CountryPlans Forum

Hey guys.  So I'm newly registered here but have been reading for some time.

My dad got me into reading this forum because he was planning to build a cabin this summer, but unfortunately he died of a heart attack back in Feburary so I decided I would keep his project alive and do it myself.

I'm not a carpenter by any means and am hoping to make this a fun experience for me and my family.

Here's the run up of the property right now so we have an understanding of what I choose to do to get started.

My dad used to have a 2001 Redman 30x80 double wide until some unfortunate events destroyed it.  So now we have all the piers still on the land and I decided I would build a 20x30 on the spot but after measuring I was able to use some of the piers that measured 24x32 so this is the size I'm going with.

I bought some manufactured fully concrete dek-blocks to use, which after talking with a few other carpenters, I believe will be plenty strong to hold the weight of the cabin.

I have a pier every 6-6.5 foot along the front and back making the 32 foot length and in the center there are 3 piers every 10-10.5 foot.   This makes my grid for the deck floor so that I can build on the existing piers.

I will be running 4x10x32 along the front/middle/rear for my beams and will then build my joists on top which I believe will be 2x8x24 or 2x10x24.  Just need to know which would be best, and the center spacing I can get away with for both,  12" 14" or 16" ???

Next, I want to have a loft that will cover 24x15 (maybe) which will be over the bedroom and bathroom,  but I want to have around a 3-4 foot wall in the loft  (12 foot outer walls total) and still have the peek at about 16 foot from the floor of the building.

I'm curious to know the pitch of roof I would have, or need to gain this height.   This would mean the ceiling above the bedroom and bathroom would be 8' and the roof would start at 3-4' high in the loft and go up to about 8' high peek from the center of the loft, again making about a 16' total peek in the roof.

I'm sorry if I'm not making much sense, this is all new to me and I'm trying to get this stuff figured out.


Thanks for such a great place to learn.

Let me say,  I love this build here, but it doesn't really have too many specifics listed on the walls/loft/pitch.

(https://i201.photobucket.com/albums/aa178/blondrtt/CIMG1471-1.jpg)

Hi! Welcome to the forum! This sounds like an interesting project, and a good way to honor your Dad.

First of all, I'm not an engineer, but there's a few things that jump out at me. We need to know what kind of piers are existing. I've seen mobile homes put on everything from a full basement to just a loose stack of bricks. Next- What do you mean by deck blocks? Are the the things that just rest on the ground? If so, they're fine for a deck, but when you start adding walls and a roof structure, not so much. You have to think in terms of a lot more weight, plus there are sideways and even upward forces on a cabin that a deck won't experience. There's no point in building on anything but a solid, anchored foundation.

As for floor joists, if you google 'span tables', you'll find recommended sizes and spacing for a given load.

The loft- Since the main floor will be 24X32, I assume the ridge will run in the 32' dimension. That gives you a width of 24'. If the side walls are 12'. and you want the peak to be 16', that gives a 4' rise over 12' (half the width of the roof). So the pitch would be 4/12, which is about the minimum in many areas for a shingle roof. An 8' peak will give you very little walking around space. Don't forget that your loft joists will eat about a foot of your vertical space, too.

Get some graph paper and start drawing some of this stuff out to scale. Post drawings of what you've got/want, and we'll dig in on it.

The piers are 2' round by 3' deep, solid concrete.  There are 13 I can use where I want to build at, 5 for front row, 5 for back row, 3 for center row all evenly placed.

What ways are there to build on the existing piers without using dek blocks?   I figured the dek blocks would work because I've seen a few other people use them, especially here:  http://www.countryplans.com/nicolaisen.html  and seen the durability of them first hand on home addons.  Here's another link to some more of the nicolaisen build,  http://www.coyotecottage.com/cabin/cabinconstruction/foundation.htm

I read I could drill into both the dek-blocks or the piers and insert a EPB44T bracket for the 4x4 posts.   Problem with this is, I'm afraid that drilling into the pier might crack it, or break it, then I'd be kind of screwed on using the piers.

The loft space will only be used for sleeping or hanging out for the little kids, I won't need much room for walking around in there.   If you could recommend something you think would be more convenient without making the roof appear to tall I'd be interested in hearing.

I'll go get some graph paper today and see what I can do about drawing up what I've got to work with.  Might be a few days before I can upload anything though.

I forgot to mention,  with the dek-blocks I had intended to anchor the cabin into the ground, just like they do mobile homes, underneath, just not real sure if it's the best idea, even though people are using them.

Welcome.   w*

Yes the home cheapo dek blocks "work." They are not the best, or even great.  I have them on a shed I built.  Your blocks sound a little different.  Also take note many dug down to the frost line and filled the hole with gravel for drainage and to lessen frost heave. The problem with placing piers on grade is you lose the advantage of the weight of the soil in the leverage equation with piers.  Piers on grade are good for speed, but severely lack for longevity of the structure.  If they are 3ft deep, bury them 3 ft. In addition the buildings you cite to are much smaller, lighter, and have more piers than what you have proposed. Also they should be reinforced with rebar inside.  If they crack with drilling, toss them right away.  You are about to put thousands of pounds of weight on them. You are about to spend $30,000 or more on a cabin like the one you cite in your second post.  It would probably cost only $100-$200 more for more properly sized piers with proper depth.   Mobile homes are on steel I-beams and depreciate quickly.  I would not use their foundations as a reference for a house.

It appears you are off with the concept of pier spacing and girder span.  There is a code chart and a short guide on how to use. It can be found here:
http://countryplans.com/smf/index.php?topic=10511.0
Five piers with a 4" bracket gives you an 8 foot span, for a 2 story center bearing floor structure.
Three piers would give you a 16 foot span in the center beams.  That is an extreme span for a girder.

"Just because something has been done and hasn't failed, doesn't mean it is good design." - MountainDon

It is good to ask first than an expensive fix later.

Actually, I have a total of 20 piers in my 24 (east/west) x 32 (north/south) section.  They are spaced every 8 foot  going east to west, and every 6.5 foot going north to south.  I wasn't going to use all 20 originally but now I think I might.

This would mean I would run 4x10x32 "wood" beams down 4 rows, 8 foot apart, down my  24 foot depth.

I would then run my floor joists on top of my beams with 12" centers.  Also, once the deck floor is built, we were considering anchoring the deck into the ground, much like you would a mobile home with bands, and anchors drilled down into the soil.

I contacted the mobile home company that dug and poured the piers 10 years ago and they said they are 48" deep according to their general specification.  Now, using 20 of these blocks in the span that I have, would it help any, even if the 4x4 is anchored to the blocks?   The blocks will be covered with dirt almost all the way to the top of the dek-blocks, which should give more support for movement, I'd think.

I know the image in post 2 isn't going to be a cheap build, but mine won't look exactly like that either.  I do believe that after searching and reading,  I should be able to build on top of these piers, with or without the dek blocks, which by the way are 12x12 and feel as heavy as 2 8x8x16 cinder blocks, which I feel would be pretty sturdy.

I'm not here to question anyones intelligence, only asking questions so I have an understanding.

How about a picture showing what you are saying?

It's messy as we're still cleaning up storm damage from the tornadoes...

(http://www.deathtrip.org/images/land2011/IMAG0427_small.jpg)

Ok, Let me see if I can work through the description with the picture.
First, if the concrete under the deck blocks is sunk 48" and is 2 ft around you are in great shape.  I would have just drilled into that and epoxied a bracket into them.  It would have been the strongest solution.  But I wouldn't worry about frost heave if that is what you are building over. In a high wind storm area, I would want as much as possible secured from the ground up and would not simply rely on gravity to hold the deck blocks in place over the concrete it is on top of.  Hopefully some on here more experienced with high wind can give you more detailed advice on that.

From the picture it appears that there are four spaces between the blocks going from the front of the picture to the back.  I assume this is the 32 ft direction in the picture.  This would mean that there is span of 8 ft (32/4=8) between blocks along the 32 ft wall.  I don't know what kind of roof you plan, but over a 24 ft span a gable roof is the most common.  That means there has to be a girder along the 32 ft span to carry the weight of half the roof, half the loft, and depending on how you run the floor, part of the floor, the proper safe sizing of that girder can be found in the chart I referenced above.  Most lumber sizing/span charts in the code are developed by the American Wood Council and should be used as a minimum standard for building. From the left to the right of the picture I see 3 spaces between the 4 deck piers.  I assume this is the 24 ft direction 24/3 = 8 feet span.  Under the code chart 2-2x10's or one 4x10 does not qualify for those spans on a 24 ft wide building.  Please reconsider your girder sizing or amount of piers for safety reasons. 

I know you are not here to question anyone's intelligence, and I don't think anyone would interpret your questions as such.  I came here a few years ago just getting started myself.  Through the help of the others here, lots of books, code reading, and a little building I understand much more now.  Proper beam sizing is one of the least understood concepts from new builders that come here.  I recommend reading the guide on how to use the published data in the building code on them (give a man a fish/teach a man to fish).   There is a lot of great advice from the administrators of this website and professional builders in that thread.

There are 20 blocks total,  4 rows of 5,  not 3 rows of 5.

If you look at the top far right of the photo, you can see there are 4 rows,  in the pic it's just hard to see the row on the far right.

From where I am standing, looking at the picture we are pointing to the 32' direction.  The blocks on the far right, and on the left run the 24' direction.

There is a row of 4 piers looking this direction spaced from top to bottom at 6.5 foot apart.   Now from the left side of the image to the right side of the image we are spaced 8 foot apart.

Here is a simple paint mock-up of how it appears in the image above...

(http://www.deathtrip.org/images/land2011/piers_paint.jpg)

Above I said there was a row of 4 piers spaced 6.5' apart,  I meant to say 4 rows of 5 piers which are spaced 6.5' apart, with 8' space between each row.

I dunno how to edit posts on here, it doesn't show me any options to do that.

I still don't understand the math.  There are four spaces created in between the five blocks that the lumber would have to span. Four spans at 6.5 ft =  26 ft.  Are you calculating the size of the blocks into the equation?  If so, are you resting the entire beam on the block?  If so, are you planning on pressure treated wood?  I thought you said you were going to use a bracket, such as the examples you cited above? Or are you planning to leave the beams unsupported by 3 ft on each end?

Oh crap, you're right, add in one more pier/block to each row.  That makes 4 total rows of 6 piers, making 24 blocks/piers total.  I didn't calculate right, sorry been a long morning.

There is right around 6.4-6.5 foot between each block per row... and 8 foot between each row.   Now we have it measured correctly.

On the 32 ft. length you have 5 piers. Unless the beams will overhang 3 ft. at each end then those piers have got to be 8 ft. apart to make 32 ft. No big deal but you will have to size the beams accordingly.

I think it is important to describe an overall plan of the structure in order to get the best help here. If building something like the 20 by 30 with loft (like the one you mentioned) there will have to be changes in the design to accommodate the 24 ft. width. 12 ft walls may be a problem. As far as the foundation I think it depends a lot on how the roof is designed. If using a ridge board then the weight of the structure will be bearing on the two outside (32 ft.) beams.

If using a ridge beam then it would carry much of the roof load and distribute the weight to the center of the house, and also eliminate the need for rafter ties. In hindsight I wish I had used a ridge beam on my 20 by 30.

There is also the option of engineered trusses which is a good one but you will lose some headroom in the loft.

If you do use a ridge beam then the load will trace down to the center of the house, making a center beam the norm though you could probably work with the 2 center beams by beefing up the end joists, essentially making them beams to support the ridge. Not sure about that though.  ???

If you don't use the ridge beam then 2 center beams is somewhat overkill, though it would work. I think they could be sized quite a bit smaller than the end beams.

Either way I think those deck piers would have to be securely attached to the footings, not really sure how to go about that. One of the reasons I went with a pier foundation was to have a decent crawl space to run plumbing and electric, which I have found very handy in building mine. You won't have much with those deck piers, something to consider. Insulating the floor could be a problem because of restricted access, there are many threads here relating to the hazards of insulating the floor before you are dried in. Definitely use PT wood for the beams.

I am planning to use a ridge beam.  I figured it would be best to use a ridge beam because of the pier/block situation and to keep weight from being forced just on the outer piers.

A ridge beam would have to span a massive amount of weight between the 8 foot span between the two center rows of piers.  Not much wood is made to be able to accomplish that.  The charts referenced above won't even come close to that.  You would need an engineer to do the calculation.  Maybe you could do an offset ridge beam like in a saltbox design.  Also you can use the code chart from above in calculating the ridge beam size.

I agree with dug, that two center beams are normally overkill on a 24 ft wide house, but since they are already there you can go with smaller joists or wider spacing and save a few dollars on the floor joists.

What size joists do you think would work for 24 foot?  I was going to just use 2x10 but if 2x8 would work, I'd use them also.

I understand that 2 center beams are overkill, but since the piers are placed there, and the spacing is that way already, I'll use it.

Also, I'm going to anchor 4x4 posts to the dek-blocks, and my 4x4 posts will have braces to make them more secure.  Also remember, we are going to tie-down the beams/frame with anchors into the ground, under the frame so there won't be any possible lift, even in wind,  just like they do with mobile homes.  The reason why is 1, because the dek-blocks aren't anchored to the piers, and because  I already have the anchors to strap it down.

As for the ridge beam... what about something like this?

(http://www.davisframe.com/About-Timber-Framing-Post-Beam-Homes/Images/UserDir/Common-Purlin-Frame.jpg)

That looks like a nice timberframe design.  I think we were on totally different pages.  Sorry.  I thought you were stick framing it.  Timber framing is an interesting way to jump into building.  Did you design it or buy the plan?

That timber frame design was done by Davis Frame Company (DavisFrame.com)

I will use that design, so that all weight is distributed evenly, and I believe it is cost effective also from just calculating.

I think it's great that you already have those ready made footings, it was a lot of work digging and pouring mine. Are the tops all on the same plane/level?

I remain wary of the deck piers though, even with the tie downs you propose. Seems like there must be a better way to do it and end up with a more solid connection.

Even with tie downs mobile homes can flip.

Oh I know they can, but I still see having 10-15 tie downs being almost as equal as drilling 24 holes in the piers and epoxying the anchors into them, per the build plans.

I have been googling and reading and a lot of people have used the deck piers/blocks successfully without much trouble at all, if any!

Also, all of the piers are smooth surfaced, but a few of them are lower than others, my buddy is letting me borrow his laser level to mark my height on the 4x4 posts, which I hope to be doing tonight, or tomorrow morning.

You'll need to coordinate with the frame builder. Each post in that frame needs to land over a footing, not just on the floor. A timberframe collects loads and sends them down to points rather than distributing them uniformly. In other words the piers you have must coincide with their frame. The dek blocks and 4x4's will not work with this frame, It'll need to be a good bit more substantial. I see cubes of block in the background. Stop and get it planned out better before proceeding.

Tonight I spoke with a contractor who is coming out tomorrow to look at the piers and to discuss the specifics.

He also said he'll drill into the existing piers to insert 4x4 post base anchors (his words) so that we can do things right, for very cheap.

Also, I'm not sure I'm really too clear on what I'm wanting to do.

I want to build my 24x32 deck floor, which the contractor said my pier spacing and count is sufficient for that, so that's what I shall do first.

As you can see here,  http://countryplans.com/smf/index.php?topic=7477.40  TexstarJim is doing a 24x32 with less piers and more spacing than I am, so I feel mine should suffice.

As for the timber frame design... I don't want to build a timber frame home... I want to build my cabin's roof/rafters like this, with the two beams running down the top instead of 1, and make those two beams come down to rest weight onto the 2 center row of piers.

I'm going to show the contractor my ideas tomorrow and see what he says, but it really looks like this would work.

Quote from: interex on June 23, 2011, 12:12:12 AM

As you can see here,  http://countryplans.com/smf/index.php?topic=7477.40  TexstarJim is doing a 24x32 with less piers and more spacing than I am, so I feel mine should suffice.

I have a comment. But first; I'm not/not picking on TexStarJim, Jan Nicolaisen or any other member posted projects here on CountryPlans forum. I'm also not/not passing judgement on TexStarJim, Jan Nicolaisen or any other projects posted here.

My point is that I selected my signature line for very good reason.

This forum does not edit the forum content for correct engineering of the designs presented. This can be safely said of pretty much any forum that allows and encourages folks to proudly display their projects as we do. Nor does the display of any construction technique by any member convey any legitimacy to such presented techniques. We try, repeat try, to steer folks in directions that hopefully results in safer, higher quality project results. The "that looks about right" approach can not be endorsed by myself. I have learned a lot since coming on board and I continue to learn. The more I learn the more I realize there is still to be learned. "Seat of the pants" engineering used to seem to work well enough back when I had race cars in my blood; I'm not sure "seat of the pants" will get you anywhere in that field anymore.

For many things I try to recycle or re-use things I have laying about before buying new things. This goes for many things other than construction. After struggling through 65 years of life I could recount attempts made to save money by re-using "things". Some have worked fine, others I'd like to forget. Some simply were not worth the efforts and compromises made in their re-use. I'm sure some I have forgotten about.  ;D Thank goodness for the passing of years.  ;)  I have a current re-purposing project I hope to display proudly and successfully in the next month or so.

Another good signature line would be something like... The fact that many buildings are still standing may say more about the conservative nature of strength of materials ratings than the design process, or lack thereof.

I stopped commenting when I thought you were building a timber frame cabin.  I don't have much experience with that and the only knowledge I have is from helping a few builds and reading a book on it.  Don_P is and a few others have a lot more experience than many in that design.  Timberframes have many different engineering approaches to carry and distribute load and force than stickframes.  I thought your piers would connect directly to the posts to carry the load from the roof and the floors directly to the foundation.  As you can see the rafters connect directly to each other because much of the pull a part force is dealt with through cross beams with large wooden pins and joints.  These are very different principles from stick framing.  Spacing is fine in construction, but proper sizing and load distribution should go with it.

I am a little confused with the type of building you are trying to accomplish (stickframe or timberframe).  You are undertaking an ambitious project of both designing and building a large cabin from scratch.  If you would like to learn more on normal design standards for different types of building, I and many others are certainly happy to answer questions and point you in the right direction to learn more.  Pointing to another building and deciding that will work for you without knowing why is not an approach I would recommend.  TexasStarJim built with larger beams and larger posts than what you proposed. His building is only one story, with engineered trusses and beams throughout in a no snow, no wind area.  It is interesting that you point to his project because there are long discussions about sizing up and bracing beams and joists for that span.  A few have pointed to published guides that show how to determine what sizing/spacing you need.  If you do not feel you can use them, there are many plans for sale.  If you have a reputable builder doing the work and code department, you will probably need a detailed set of plans anyway.  If you have any questions, just ask.

Okay, the floor/deck is not part of my concerns anymore, right now I'm trying to figure out the roof beams.

Here's what I'm trying to say/understand...

I could do my rafter beams similar to the timberframe home's image on page1.  Meaning since I have two piers down the center of the proposed area,  I could run support up the side wall to the peek and run purlin style rafter beams to the other side, where I would have 2 at the top instead of 1,  to run my rafters over.   This would distribute the top weight of the rafters not only on the outer walls, but the end 2 center piers.

I know it's really sounding difficult coming from me, and I can't draw for anything to try and show you what I mean, but if you take just the roof from the Timberframe image I posted, you might understand the type of roof I'm talking about building.

We've already decided to have the piers drilled and anchors inserted, to do away with the dek-blocks.  I've been reading, and reading, and calculating but the thing is, over half the projects I've read through do not follow the guidelines for standard building rules/codes, so I do understand that a lot of people do build without following them precisely.

I'm not familiar with that roof system so I really can't comment on it but I think it would be a lot simpler to use a single ridge beam. You mentioned you are not a carpenter and as a first time builder myself I can testify that even a simple design is plenty challenging. There are ways to spread the load from a single beam to the foundation you will have (pretty sure), and some really good people here that could probably help you with that.

QuoteI've been reading, and reading, and calculating but the thing is, over half the projects I've read through do not follow the guidelines for standard building rules/codes, so I do understand that a lot of people do build without following them precisely.

No doubt about that, but I (and others I bet) have done some things on my build that I've come to regret after learning more on this incredibly informative site. Folks here don't judge but will shoot from the hip.

I don't see why you couldn't run two ridge beams instead of one.  I assume the 8 ft in between the two ridge beams would need a rafter tie and a ridge board still.  Again, just like a one ridge beam the load has to be carried directly to the foundation.  You can use the beam code chart to calculate the proper sizing/spacing of this too.

Quote from: interex on June 24, 2011, 10:24:06 AM
  I've been reading, and reading, and calculating but the thing is, over half the projects I've read through do not follow the guidelines for standard building rules/codes, so I do understand that a lot of people do build without following them precisely.

Quote from: dug on June 24, 2011, 11:05:08 AM
No doubt about that, but I (and others I bet) have done some things on my build that I've come to regret after learning more on this incredibly informative site. Folks here don't judge but will shoot from the hip.

Mountaindon may not want to single any members out, but I will.
Take this one for an example.

http://countryplans.com/smf/index.php?topic=7305.0

This member wanted to do something "different."  To go with another method that was easier that he had seen in an old book.  He also traded quality and normal design for expedience.  By the 3rd year the foundation has already shifted.  He will be lucky if it lasts 10-15 years.  Try not to learn the hard way like this moron.

And I was thinking "Geez take it easy on the poor guy"  :D... we are our own harshest critic sometimes.

There's nothing wrong with a principal purlin common rafter roof, look in many older barns. The aisle was down the center with stalls on each side, this is how they were supported. The "problem" I see with using that system here is that those purlins will need to be supported through both floors on posts down to the footings. It's going to really limit your design options inside.

This is another option to throw into the mix to think about.
I've supported the main floor on your existing piers and the roof is a "cantilevered attic truss" that spans the full 24' and bears on the outer walls. The "room" downstairs is entirely open, walls can be anywhere. The upstairs "room" is drawn at 16' wide and has about 10' of width at 8' high.
(https://i180.photobucket.com/albums/x109/windyhilll/cNTTRUSS.jpg)

If it were mine there would be a full perimeter foundation to stabilize and support the structure above and the center 2 rows of piers would be used to support the main floor girders. There are more options there. I would not proceed with any work until the plan is much further along.

Okay, sorry guys been gone working a while.

We have planned a different route and I'm looking for opinions.

Would a 24x32 cottage be supported well enough on 4x4s or 6x6 post piers?

To recap, I have 20 total piers.  4 rows deep of 5 piers per row totaling 24Lx32W.

My next question is, would running my 2x10 (or 4x10) floor beams be better anchored on top of the post piers or anchored to the face/side of the post piers?

I agree with Don_P's suggestion of the attic trusses. Also, with a house of that size and in tornado country I would have as much weight bearing as possible go to a full sized and anchored perimeter concrete foundation. The piers would work great for the interior floor girders.

When doing girders that support the floor joists you want a solid 4x4, 4x6, or 6x6 (depending on the size of the girder) directly under the girder and attached with an anchor such as these: http://www.strongtie.com/products/categories/post_caps.html

(http://www.strongtie.com/graphics/categories/AC-post_caps_bases.gif)

If you finally do use the pier and beam for your perimeter foundation you will want additional diagonal bracing (4x4s?) as well. Also some way to tie the posts into the buried concrete piers. Tie all the major parts of the house together with straps and anchors (foundation, floor, wall and roof). This will give you more rigidity and protection against uplift.

After talking with a few contractors, 1 said we could use the piers to do a pier and post build with 4x4 posts anchored to the piers using 3" by 1/8" angle iron, and with the amount of piers we could get away with using 4x4.  Another said the same thing except using 6x6, but said the 2x10 or 4x10 beams could be bolted to the face of the post instead of on top to reduce any front to back movement?

I am going to use my existing piers with posts and anchors but by reading and consulting, I am unsure of the post sizes and how to anchor my wood beams to my posts, and if I should do my joists inside the beams on build them on top, if that makes sense.

Do not bolt to the face. The bearing area for the entire house load is concentrated on the upper half of the bolt(s). The steel can take it but the wood can't. Sit the bottoms of beams on something with broad contact area to avoid crushing and splitting.

4x4's are for mailboxes.

A pressure treated framed and PT plywood skirt wall connecting the posts would give a great deal of lateral bracing.

Okay, you're not really giving any answers.  You said 4x4 is for mailboxes, does that mean I should use a 6x6, 4x6, what?

Giving direct answers to questions helps a lot.

I thought that was your original plan to do 4x4 with a 4x10 across the top?  Don_P knows the science of building better than most.  He has forgotten more than I know.  The best I can do is point you towards published guides of minimum safe sizing.  Are you going with a stick built this time?  If so, please refer to the code guide posted in my original post.  It shows how to calculate how big the beams have to be and how much wood they must bear on. I would use caution with either of those contractors if they are suggesting a 1.5 story on a 4x10 over a 4x4 for an 8 ft span on a 24 ft wide building.

Also, you should refer to mountaindon's guide to planning.  Here:
http://countryplans.com/smf/index.php?topic=10675.0

Houses are designed from the top down.  Knowing how to size the foundation without knowing how and where the loads of the house will fall is just a guessing game.  

BTW.  I know a guy who did the "hang the board on the side" method.  He did it for a building with an 8 foot total width and spacing of 5'-10". It works fine for decks.  It is ok for sheds.  I would not recommend it on something you want to last.

http://countryplans.com/smf/index.php?topic=7305.0

Interex,

Don was trying for a bit of pointed humor on the 4x4 comment.  Sometimes that doesn't come through in print (grin).

What he meant was "4x4 is for mailboxes, not houses" as in, he would never consider using posts as small as 4x4 for any significantly sized structure.

As Squirl mentioned, Don is probably one of the most knowledgeable people on here regarding structure sizing and strength.  I'm a newbie myself, and if Don tells me not to do something, I'm going to really sit up and pay attention.

In this case, he is recommending you use minimum 6x6 posts, and that you lay your pressure-treated beams ON TOP of those posts (not bolted to the side).  While the contractor is correct there is a concern with lateral movement, if you attach a treated plywood skirt around the perimeter (tying together the treated beams with the posts) it will stiffen the structure up nicely.  If you want a graphic example, I'm sure there are some folks that can show you pictures of similar.

As a fellow newbie, let me say that you are starting what I would consider a pretty aggressive first attempt. 

If you can, I would start by building a smaller structure, say an 8x10 shed at the site.  This would help you get a feel for what you can do, test out how well you understand the techniques, and also how much time, stamina, and patience you have.  I am going that route. 

I'm not telling you that you can't do it successfully, but frankly it sounds like you are trying to teach yourself design AND customize the design on the fly.  That is a lot tougher and more complicated than most folks realize.  You would probably be better off buying a complete design and NOT trying to tweak it, or paying someone to make a custom design it for you, so that you can focus just on building something guaranteed to last.

Okay, so with 6x6 posts, is 4x10x32 big enough for beams?

Should they be 6x10x32, maybe even 4x12x32, or 6x12x32 ?

Remember, I have 4 rows of piers running 32 feet, with 5 piers per row totaling 20 piers, with about 8 feet between the center of each pier running the long direction (32'), and 8 feet between the center of each pier running the short direction (24')  I keep being told this is overkill but if it's overkill, wouldn't it be used in any advantage?

Reading on here, so many people are using so many different sizes for very similar builds/projects.

I'm asking questions to understand what people think, to know from people who have experience.

I've lost track of what this foundation is supporting. A refresh on the current plan would be good. Snow load for roof (available at county building inspection department)? Full upper floor or just sleeping loft? Roof type; truss framed or standard rafters with ridge board or structural roof ridge beam or what? These choices will affect the foundation design.

Someone pointed out earlier that design begins with the roof and from there goes down one level at a time. That is bang on! Design also takes into account special things like; library shelves full of books, king size water bed, mega sized gun safes and refrigerators, hot tubs, extra large bathtubs, weight/exercise machines, stone floors, etc.

Lots of folks do different things on projects that appear similar. Some of them have done a better job on design than others.

So without knowing what is to be supported choosing foundation member sizes is a crap shoot. I don't have the time to re-read the entire thread to try to figure out what the upper levels to be supported by the foundation are.

With all that said, a quick look at IRC Table 502.5(1) it would appear that for a structure with two floors with center supporting beams (only one down the center of each) and a roof resting on the side walls with 30 pound/sq ft snow ground load, the outside beams should likely be built up from (4)2x12's in order to safely span the 8 foot distance. The center two beams could likely be smaller if they were just supporting average interior loads. If they are supporting some sort of load from the roof then my guesses are out the window and an engineer could provide the best/safest answers.


I don't mean to sound harsh, but anyone needs the facts to stand a chance at providing valid advise and there are so many projects and questions it can get difficult to keep them sorted out.

I plan for the center peek of my roof to be 14'-16' from the floor of the home.  I am looking at just a single floor, with a very small loft on one end, just enough room for kids to climb up and have a little bed/cot etc.

There won't be anything inside but a small couch, tv, table, fridge, 1 man shower, toilet, wood wall panels, peel and press T&G floor planks, etc... nothing too "fancy".

Also, I want to go with rafters instead of trusses.  I want to run 2 support beams along the roof from the center row of piers along the roof on both ends... to allow weight to be distributed to the center row of piers, maybe?   Like the image below.


(http://i52.tinypic.com/wqv5td.jpg)

I see. Are those planned 32 ft long roof beams to be supported only at the ends, within the end walls? Or would there be intermediate support posts as well?  If only supported at the ends then the footings under the end walls may have to be substantial. Getting into unfamiliar ground as far as my own experience.

The 32' roof beams will have support inside, roughly 10-12' from one end, which leaves 20'-22' span the rest of the way through the open ceiling.

The reason why 10-12' is because this will be where the bedroom/bathroom wall is, which is also where the loft will be.

I wish I had a way to draw it out.

"I wish I had a way to draw it out."

Start with graph paper - squared paper to scale

Down load google sketch up for free, and use that - its 3D and relatively easy to do

I've only been using about 6 months

I use it for my outside views and then use Progesmart cad for the detail dwgs

there are some framing dwgs on my thread - just using sketchup, it gives you a clear view on how things will go together.


http://countryplans.com/smf/index.php?topic=9588.0

A ridge column to foundation will be a lot easier to do and complete the calculations than what you have dwn so far

Ditto what UK4X4 said about graph paper. One of the best planning tools ever invented. I use a drafting quality vellum for the serious drawings but start out with plain old graph paper for roughing out an idea. The advantage to vellum is its availability in larger sizes and the paper itself is very erasable; you can erase many times and erase fully without suffering any deterioration in the paper surface. Staples and Officemax carry it as do other like stores.

Once I get a plan I think I like, I often build a model at 1:24 scale out of 1/4" foamboard you can get at Staples. With a hot glue gun  it goes quick. I bought some cheap 1:24 scale dollhouse furniture on ebay to get a feel for the room sizes. Yes, I'm 57 years old, and I play with dolls!

 The roof can be supported on purlins as mentioned before. The posts would be better if continuous from footing to top members, think post frame construction. The walls then brace the posts extending below.

(https://i180.photobucket.com/albums/x109/windyhilll/postframe.jpg)

That is EXACTLY what I want.

That looks really good!  Thank you so much.

I don't know how to edit posts, but I forgot to ask...

On the post beams, would the posts for the loft, and the supports for the purlins not be able to be put on top of the beams? 

Would I lost support on the beams if I did this rather than had their own individual piers?

The lateral loads, usually the wind pushing on the building, on a typical foundation are carried from the house down to the ground through and around the perimeter foundation walls. Pier, girder, joist and post above would be the typical way of supporting the internal posts in platform frame construction. However that system also requires a perimeter foundation to take the racking loads down through a wall to the ground. What you are proposing and what I've drawn is quite doable but well outside of the cookbook tables and methods in the codebook. When that sketch is close enough to doodle dimensions on it's time to go talk to an engineer to work out the particulars.

So, this is my progress so far...  tomorrow all the beams and end braces will be done, then time for the joists.

May not be a preferred method, the way I bolted everything like this... but it seems to be much stronger and has so far been less expensive doing it this way.

The braces are all bolted on both sides of the posts/beams.  The beam was very sturdy and appeared to be very strong and with having 40 posts for a 24x32... I don't see myself having much of an issue with doing it on these huge piers.



(http://i55.tinypic.com/wi3fdg.jpg)

(http://i51.tinypic.com/wjxq9y.jpg)

(http://i55.tinypic.com/2pr5xmq.jpg)

(http://i55.tinypic.com/16gg1o8.jpg)

(http://i52.tinypic.com/6rn71d.jpg)

(http://i53.tinypic.com/2lxgvaq.jpg)

This is well connected but is unbraced. Welding the flat plate into T or L sections or attaching Y braces is what provides lateral rack bracing. Steel and fasteners in contact with treated should be galvanized or at least very well primed, the copper in the treated wood in contact with mild steel is a low voltage battery arcing into the steel whenever moisture is present.

Do you mean Y bracing under the beam on the sides of the post?  If so, I've not got that far yet.

As for the metal, it will all be coated with what is similar to that used on bed liners/undercoating, to prevent rusting, so that should cover the current/voltage concerns.

Coating on the face that is in contact with the PT wood is the important face.

I would suggest getting a load trace as has been mentioned earlier.

Doing solid blocking at every post, and tying beams and posts together with heavy bolted plates as you are doing is a good start. Stick framing the walls and floors and then sheathing everything with well nailed structural sheathing will also add a lot to the rigidity. Still, you don't want to get up to the loft floor and realize there is a new load coming down you hadn't anticipated.

Some questions pop up with the work so far:
• Is there enough room under the girders to get around the crawlspace and work on plumbing and wiring? Minimum is often 16" under joists and 12" under beams/girders - and more is better - especially for guys of any girth.
• Is there a moisture stop between the posts and the concrete pier?
• Do you have to consider insects such as termites?

Coating will be on both sides of all metal, even the angles on the strike anchors at the piers.

As for is there enough room?  Yea, at the north end we're at 16" high on the posts, at the south end we're at 8-9"... and probably enough to do what needs to be done.

As for a moisture stop, I have black plastic that I probably should put down... completely overlooked that part.

We haven't ever had an infestation where I live, not to say it can't happen... but any preventative measures to ensure there isn't a future problem are useful.

A piece of asphalt shingle makes a good moisture stop under a post. There are metal termite shields (http://goo.gl/Zp2je) that force the critters into some discouraging acrobatics to get to the eatable wood but that's probably not needed by the sound of things.

If they are a little larger they also double as good rodent shields. Rodents love elevated floors over posts.  The wider the better.  

(http://content.answcdn.com/main/content/img/McGrawHill/atchitecture/f0987-03.png)


I'm not sure how effective they would be at 8".

Okay...

All beams and posts came down, all metal was treated with an undercoating/bedliner type spray which was recommended to protect the metal from the elements, as well as to the PT Wood itself.

Everything turned out rather well, and is all assembled.  Once all the bolts were back in place, I coated everything on the outside a second time to fill in any gaps, etc...  And just so it is out there, each post is plated on both sides with 1/8" steel, using 3/8 (2") screw/lag bolts.  We used 10 plates and 60 bolts per beam/row.

So far my cost on the metal/coating and bolts is easily under $150.

Tomorrow, depending on the rain, I should have the beams ends cut evenly and the ties installed.

It's really strange, but using my 5' level/ruler everything is perfectly level from end to end on all beams... but using my 2' level/ruler, a lot of it is off level here and there on each beam.


(http://i56.tinypic.com/16kwfpt.jpg)

The longer the level the more accurate... if the level is accurate to begin with. Turn them around and double check when in doubt. A short level is finicky. Our mason brought out his machinists level to show this past week. It's good to 5 ten thousandths per foot and cautions about walking near or even breathing on it... too much accuracy for my work! A transit, water level or laser would be best for your girders if you can get hold of one. Do brace the piers both within the row and 90 degrees to that, from row to floor before getting much weight on them.

Quote from: Don_P on September 04, 2011, 06:57:34 AM
Do brace the piers both within the row and 90 degrees to that, from row to floor before getting much weight on them.

You lost me here... can you explain a little more?

The posts can be pushed over either front to back or side to side so they need to be braced within the row and between rows, make sense?

You want to triangulate the posts with 45º braces to the beams. This adds rigidity to the floor and foundation framing. Installing braces the other way - from the posts into the floor joists - helps brace the other direction.

Right, I just haven't got that far, for the 45 degree braces under the beams.

Today was a good day, we got a lot of things done, and hopefully tomorrow I will be able to get all the bracing done.

Curious, can SYP (non-PT) be used for the joists instead of PT ?

I'm putting black plastic down over the beams before I put the joists down, and will be putting insulation between the joists.

Just making sure I don't over do it, nor under do it, ya know?

Treated is required if the bottom of the joist is closer than 18" to the ground. You don't want plastic on the bottom, cold, side of the floor assembly, it'll condense.

Measuring today, it appears that the top of each beam is 18" or above in every location except one, where it is almost 17 1/4 inch.  I'm probably going to just dig that mound of dirt out and make it the same.

Therefor, untreated SYP should be okay.   

Another concern... if I put the joists up today and it rains before I can get the insulation down and covered, will the joists be okay, being untreated?

Lastly, if putting insulation down between the joists, how do I hold it up if I can't use plastic?

QuoteAnother concern... if I put the joists up today and it rains before I can get the insulation down and covered, will the joists be okay, being untreated?

Once it is up and nailed in place standard lumber can take quite a beating from the elements and still be fine, I lost count of how many times my framing got soaked. A bigger concern would be keeping the insulation dry, which is not as easy as it may seem. Tarping will work O.K. until you start getting the walls up, but then becomes difficult to impossible. I think it's worth considering waiting until the roof is up before insulating the floor, even though it may be harder then.

QuoteLastly, if putting insulation down between the joists, how do I hold it up if I can't use plastic?

There is a thread that covers that pretty well here-

http://countryplans.com/smf/index.php?topic=11124.0 (http://countryplans.com/smf/index.php?topic=11124.0)

Thanks for the reply Dug.

Looks like I'm off to buy my floor joist lumber today since it's the last day of a really good sale, I'll be saving about $130 compared to off-sale price.

Would it be safe to put down something like 1/4" mesh on top of the beams, before the joists are installed, to cover the entire span of the foundation?

QuoteWould it be safe to put down something like 1/4" mesh on top of the beams, before the joists are installed, to cover the entire span of the foundation?

Not sure what this is asking. Is the mesh wire? Are you trying to keep the foundation dry?.. protect the beams?

All I'm trying to do is keep the floor warm in the winter time.

I'm asking what measures I should take in order to do that.

Quote from: interex on September 04, 2011, 07:22:03 PM
Right, I just haven't got that far, for the 45 degree braces under the beams.

One thing to remember is that any bracing or connection is usually only as strong as the fasteners.

A few posts back in the thread it was mentioned that the steel plates were fastened to the beam and poier material using 3/8" diameter lag screws that were 2 inches long. The engineering advice I have seen on lag screw diameter and length to develop maximum strength calls for the Length of the threads engaged in the main member to be at minimum 8X the diameter of the lag. That would be three inches of thread should be engaged in the main member for a 3/8" diameter.  

The main member here would be the beam or the post and the steel plate is what is known as the side member, or member to be secured to the main. The main member is the larger member, the side member is the piece that the lad passes completely through.

The maximum strength being talked about is the shear strength of the connection. Withdrawal strength is much less than shear, as a rule; especially so if the thread depth in the main member is less than ideal. Maximum strengths are developed with proper sized pilot holes in the main member; 9/32 in softwoods for 3/8 lag.

http://countryplans.com/smf/index.php?topic=6925.0

Just threw all that in for future readers/viewers.



Half inch is the minimum recommended diameter in code, if I recall correctly.

I used 1/8" steel with 2" lag bolts, so that means I have 1 and 7/8" bolt into my post and beam, is that not acceptable?

Also, while 1/2" diameter might be recommended, will not 3/8" diameter be acceptable?

I have a total of 12  3/8" diameter (2" long) per post... 3 on front, 3 on back per post,  and 3 on front and 3 on back per beam...on the plating. 

To answer the earlier question about insulating the floor. Go ahead and install the joists and subfloor and then all framing and all up to the roof. Once fully died in and your joist cavities have all the plumbing and wiring installed then do the insulation and fill to (at least) the bottom of the floor joists. Then put a product that is an air barrier but not a vapor barrier, such as Tyvek on the bottom followed by the mesh you suggest which will be the critter barrier. If you are doing a critter proof skirting you can eliminate this last step. This assembly will keep air from carrying away heat from the floor insulation yet allow the flooring to continue to dry out.

RE the bracing bolts. What is acceptable is a question for your inspector or perhaps an engineer who knows all the specifications of your specific soil, lumber and local wind and earthquake zone. The information Don is sharing are guidelines for getting the the most bracing support out of the bolts and hardware you might consider using. Certainly using shorter bolts is better than no bolts or using just nails.

Just to make sure I get the right joist ties... Are the Simpson Strong Tie Hurricane Z-MAX ones from the link below okay to use, to secure the joists to the beams?

http://www.lowes.com/pd_90575-72913-H1Z_0__?storeId=10151&Ntt=90575&UserSearch=90575&productId=3047195&N=0&catalogId=10051&langId=-1

I believe those are some of the stronger standard hangers simpson makes for uplift.  Also they give better lateral support many other hurricane ties that size.

http://strongtie.com/products/connectors/H.asp#tables

It looks like it is stronger than many, but less than all.  It depends on the application.

That would be a good choice.

Thanks for the replies.

I'm going to just get the Tyvek and roll it out and staple it to the beams, then install the 2x8s.

Then this weekend I will run the water/waste pipes, then insulate and install the flooring and just tarp the floor if it looks like it will rain.

I will only need to T off the water pipe going up into the bathroom, then over into the little kitchen as we have 2 small tankless electric heaters to supply both areas.

Okay, so today I decided not to put down the Tyvek and started working on my joists.

I have triple checked my beams over and over again and they have maintained a very fair amount of levelness.

Tonight, I installed 3 of the joists and they all seem to be fairly level with eachother, except one, which shows it is much lower than the others in one spot, not the entire length.

I'm starting to get worried about it, but someone else tonight told me not to worry about it.   Is this a sign of undersized 2x8s or possible warping?

Another thing I'm thinking of, while I'm at it...  what does everyone do to cover/hide the posts?  I can't use blocks because there won't be any room, and I don't really like underpinning all that much.

I could go with something like half log, or quarter log from the beams all the way to the ground, but that may not even be the best idea... I really only have about 1 and a half, to 2 inches to work with the north and south walls, and about 2.5 - 3.0 inches on the east and west walls, at the footing.


(http://i52.tinypic.com/kf5mx3.jpg)

Sight down the length and crown all joists, or horizontal members, up. Pich a crown direction and have a "rule" for studs crowning them all in the same direction. If there are any joists that are significantly off either reject them or slide your level around on its neighbors while planing, sawing or hewing it down to level.

I've seen them hidden by almost everybuilding material under the sun.  Don't use OSB.  One person I saw on here used rocks built up like a mortarless stone wall.  My preference would be pressure treated 1x boards or PT plywood.

This morning I was actually thinking about PT plywood and some really thin white stone mortared to it... But I dunno anywhere locally who sells stones like that cut so thin.

Okay, so lastnight we got the joists all done.

I noticed that the last 3 or 4... we didn't keep them straight and that have a very slight angle to them... and I have no idea why... might be that my guide board warped in the last day or so, but I don't think it will hurt too much.

I didn't get a chance to get a picture because it was after 9PM when we finished, but hopefully tomorrow I can get some.

Before I lay down my sub floor, what is best to put atop the joists?  felt paper?  And what thickness of t&g plywood should I use?

Use a 3/4" T&G subfloor panel. Install with the appropriate space between the joints. Many people will put down the T&G with construction adhesive and ring shank nails or screws.

Here is more step by step info: http://www.diyonline.com/servlet/GIB_BaseT/diylib_article.html?session.docid=1463

Your lumber yard may have more specific information on what products work best locally.

Just for knowledge sake...

How thin can wood siding be on the outside?

My local saw mill said that 7/8" is good for homes around here if properly treated... but I want to ask here.

The saw mill can cut 7/8"x12"x14' at $0.45 per board foot, making it about $4.73 per board.

Check your math, he'll be billing for 4/4, or 1" thick, X1' wide X 14' long X.45 =$6.30 per board.

That will be fine thicknesswise, do plan out your window and door trim, likely 2x material. Many old farmhouses here are slapboard sided with 5/8x6" poplar siding. I've removed some from as far back as 1865, it was done but had held up for a mighty long time.

He said they would bill at the exact board foot measurements or 3/4 or 7/8 inch, which ever I choose, not rounded up if I ordered large quantities.

I will double check to make sure tomorrow, but even if I went down as low as 5/8 or 0.63 inches... and they didn't round up, that's an even bigger savings.

Also, is $0.45 per board foot good or too high?

Sounds pretty good to me, depending on the type of wood.. We pay $0.35/bf for rough-sawn spruce, (and it's really roughly sawn...). Twice that for cedar.

It does depend on species and grade but that is quite reasonable. Generally 4/4 and below gets billed as 1" thick so he's also being quite reasonable if he's billing for exact thickness. I paid .50/bf just for portable sawing service last year, my logs.

I wouldn't go down in thickness at that width.

His price is $0.45/bf for his logs, or $0.25/bf for my own logs.

We have several acres of trees but none that would be that beneficial for our cabin.

You're saying 5/8 is too thin for 12" boards?  What about 5/8 for 8-10" boards?

Okay, so I've got my foundation all finished, all my joists tied and boxed in.   I have purchased 18 sheets of advantech 23/32 plywood (subfloor) and 2 rolls of 15# felt paper.

I'm ready to lay my floor down but lastnight I spoke with my general contractor friend and he was asking about the beams I want to run above the loft, the 32' span (longways).

I have posts to set the beams on but there will be close to a 24' span over the main area where there won't be any posts to rest the beams on...  so my question, or concern is... how big of a beam would I have to make or use in order to have the proper support over this 24' span?

My friend said to build a plywood box beam, but still said he was unsure if that would even be enough.   I was thinking about making  4x10 or 4x12 beams but need to know what the forum thinks about this.

We figured out roof pitch would be close to 6/12 and while it does snow here during the winter months, it isn't generally enough to really bring a lot of concern with.

You need to get some local engineering help with the beams and posts before you go further.

The engineer will do a load trace following and accumulating the loads of the roof down into the planned beams. Then those beams need to be supported by posts and foundation pads. The sizing of a beam with a span of 24' is likely to be quite large and its support will be an important part of your design. This is well outside any "rules of thumb".

All 6 posts going up to support the ridge beams will be sitting on top of the concrete piers underneath.   The piers are rather large as stated previously back in the thread.

The only other option I have is to run a single ridge beam at the very top center instead of running two 8' in from each side.

I dunno which would be better though, I thought running two would be easier, and give 8' span between the beams in the loft, and still look nice.

I don't currently know any engineers who could help me figure out the ridge beam issue.

You are definitely in engineer territory.  24 feet is a pretty extreme span for any beam, especially in a snow load area.  In my calculations, I couldn't find any engineered beams that fit. The largest size beams in code charts on only a 20 ft wide building is rated for 14'-1".

In addition you need to check the load to the piers and soil.

Soil load is rated in psf.  Averages range from 1500 to 3000.  Even at your pier size with a 24' span on only a few piers, it sounds like you are exceeding the rating of most soil.  You have to calculate the load from the roof, plus the load from the floor on those piers, divide that by the square feet of soil that each footing rests on.  If that is greater than the bearing capacity of your soil, you have a problem of those piers sinking.

Okay, so a single ridge beam at the top center to tie the rafters together is better than trying to run 2 beams 8' in from the outside walls and resting the rafters on top of it?

Just trying to make sense of this.

Neither you are trying to put too much weight with too little support.  A 4x12 would be so severly  undersized for that span as to risk failure. I am trying to say that without understanding the principles of the design and load distribution, an engineer is needed.  You are taking your life or someone elses in your hands if this collapses.  My recommendation is to not just wing it.

Danger Will Robinson.

To put it in perspective you are distributing tens of thousands of pounds of roof load or 3/4 of the roof load to six posts.  In addition these posts piers will be holding some of the floor load.  While concrete is rated to handle that kind of load, wood and soils are not.

I'm asking about doing a standard rafter setup, like this...  disregard the 2 beam setup from before.

My outer walls should be able to handle this.

(https://i223.photobucket.com/albums/dd127/MaineRhino/Mountain%20Camp/10-22-2007017.jpg)

The example shown is a standard ridge board with nothing I can see to tie the walls together except the rafter tie in the foreground. In the loft area the joists should run the other direction and tie the load walls, and rafter ties need to be on every rafter in the open area. I built my roof this way and used beams only every 4 ft., but I learned here recently that IRC now says ties on every rafter.

I understand that, I was meaning to run one ridge board at the top, instead of two ridge beams spaced 8 foot apart as initially suggested by myself.

The roof you have shown is not one to copy.

All depending on how far southern, If mid southern you are probably 20 pound per square foot snow load. assume 15 psf for dead load, the weight of the roof materials, or 35 psf total load. As I remember your pier layout dictated the 2 rows of roof support beams, I'm guessing your friend doesn't know this. Using 2 24' span roof beams lowers the load per beam and the load per pier. Lets do some cyphering.

With 2 rows of roof beams, they are 8' apart. If we take a slice across the 24' wide building in the 24' long open span the left wall supports 4' of the roof + the overhang (I'll assume 2')... 6'.
6' of tributary width x 35 psf= 210 pounds per lineal foot on the outer walls.

Each roof beam supports4' of roof between the wall and the beam and halfway to the next beam, 4' for a total tributary width of 8'.
8'x35psf=280 plf on the beam

The span of the roof beam is 24'.
280 plf X 24 feet= 6720 lbs uniformly distributed on a 24' span.

If you look at the roof table for LVL's it should show that a double 14" LVL (3.5" x 14" total beam dimension) will work for each roof beam at that span and load. The supplier will do this math.

Each end of those beams will then be supporting 3360 lbs, add this to any floor loads for the load being delivered to the footing. This all seems in range.

Okay, remember, we're working with 32' long by 24' wide.

In the illustration you made shown below...  you can see where the 6 posts would be to support the roof beams.  We have 6 post total, 4 on the south end, and 2 on the north end.  The south ones are 8 foot apart side by side, and north to south... and the north ones are 8 foot apart side by side.

The span for the southern 8 foot will be covered on the southern 4 posts, and the other 24 foot will be on the northern 2 posts.

I understand that LVL is a strong wood, but why is it better to use as opposed to built box beams, or making 4"x14"x36 (total) beams?  

Would a home built beam of that size not be able to support that weight, or the total uniform weight of the roof, and if not, why, if it could be explained better.


(https://i180.photobucket.com/albums/x109/windyhilll/postframe.jpg)

LVL's are stronger and stiffer than "dimensional", sawn 2x lumber. 2x lumber is in turn stronger than solid timbers. This has to due in part with the grade of material used. In part it is due to the distribution of defects, one large defect in a timber controls the strength where if that same defect were sawn into boards and the location if the defect was not continuous through any one ply the beam would be stronger. And in part the stiffness is due to the glueing of the plies together in an LVL.

Fb is the value for bending strength,
In an lvl fb= ~2750 psi
In a typical SPF 2x it is ~1250 psi
In an oak timber it is about 750 psi

Stiffness is in lvl about 2.0, in dimensional about 1.6 and in heavy timber about 1.4

Horizontal shear in an lvl is about 275 psi, in dimensional about 150 psi and in a solid timber about the same as dimensional.

It will take a much larger sawn timber to do the same work as an lvl.  (these numbers are approximate from memory but are close). We can size it in sawn or heavy timber, but it'll be a monster.

Depth is very critical to the strength and stiffness of a beam. In determining the section modulus used to find the shape of a needed rectangular beam width is multiplied by depth SQUARED, depth makes a beam stronger and stiffer much faster than making a beam wider.

The beam most likely can be 36' long, the supplier of an lvl can do all the checks required. They will be able to give you a printout showing the load reactions on each of the 6 posts to aid in your load trace.

Basically the short answer is that it is not going to make much sense to try to fabricate a beam of that size on site. The lumber would be very special order.

Edit;
I just checked it very quickly on Ilevel's Forte software;
A double 14" lvl checked for me if 36' long but required a triple if it is just spanning the 24'. Interesting if you think about it, the 8' backspan is helping to counter the load on the 24' span. this comes with a cost, the reactions are -109 lbs at the south post in the loft, the beam is actually pulling up slightly. The interior loft edge post is experiencing a ~5000 lb load and the north end posts carry ~2400 lbs.

No solid sawn combination passed, a 6x14" glulam also checked.

I thought you had a slightly higher snow load of 30 psf.  I had worked through a few calculations, but do not have the knowledge surity to do the calculations that Don_P does.  My calculations were coming up with 10,000 lbs per beam.  Or 5,000 lbs per foot with additional weight of two floors.  I re read the beginning and the concrete piers bear on 3 sq. ft. of soil.  If you have very low bearing capacity to the soil, with the floor load this could still be a problem.  Just something to double check.

BTW don, which product guide are you looking at?

LVL perform a lot different than glue lams.
http://www.americandreamconsulting.com/Charts/AnthonyGlueLam.pdf

Squirl,
I have GP's residential floor & roof systems product guide, 2.23 mb if you google it should pop up.
I was also playing with it on Ilevel's Forte software, a free download.

The codebook snowload map shows 20 psf from around Rockford south.

Your Anthony products link is a good read and compares other materials I didn't above. Go to pg 11 and scroll down to 24' and over to better than 280 lb total load. A 3.5"x 15.25" or a 5.5"x 12.375" passes there. I'd step to the 13.75" deep beam, it was close with the 12", deflection would be getting heavy.

This gnawed at the back of my brain while I was working on this yesterday and I ignored it. I had an email from PEte that I agree with. I'm late at the moment and have the client's in so may not get back to this for a little bit but this is worth posting to think about.

Quote
RE: 24x32 in Southern Ill., reply #101
Take a look at your AITC Timber Const. Manual, at the beam formulas for a symmetrical two span continuous beam, your 12' rafters, probably formulas #29: I would leave the ext. wall reaction at (2'+4')(horiz. projected roof load), that is their R1 or V1. This allows for some ice build-up weight on the overhang. But, notice that the center reaction on the cont. rafter is actually (10wL/8), their R2 = 2V2; which is the load on the LVL you are talking about. Furthermore, the location of your LVL is just about at the location, w.r.t. the ridge, where a snow drift is deepest on the leeward side of the roof. I'd bump that LVL loading up a bit. Finally, watch out for the gable wall post on the short 12' loft span and the possibility of uplift from the LVL beam. Then design the rafters for the full 12' span, or maybe 10', and then allow a small birds-mouth over the LVL.

I'm seriously thinking about scrapping the roof beams all together.

I think it would be too much on weight, and work to have them.

Engineering, more advanced than I.  Normally engineers charge out the wazoo for information that Don can give.

So I will describe my original concern about the piers a little better and hopefully someone can weigh in on my calculations.  Don_P Came up with an interior loft post carrying 5000 lbs from the roof load.  Now for the loft floor, it looks like it carries 4 ft evenly around each posts for the loft.  So each post would carry 4ftx8ft area or 32 square feet. At a load of 40 p.s.f. that would be an additional 1280 lbs per center post for the loft.  Now to add in the first floor.  This look like it carries an even load of 4 ft around but the floor is complete and a half like the loft so an additional 2560 per post.  This adds up to 5000 + 1280 + 2560 = 8840 lbs per concrete pier.  With each pier bearing around 3 square feet on the soil, that is roughly 3000 pounds per square foot in my equations.  You would have to have pretty good soil, at least better than the clay soils I deal with.

Interex, describe plan B, the load isn't going away, how are you thinking of building it?

The way ive seen this.done in timber frame with trying to keep the beam size down is to.use three.beams. One in the middle and one each side of it half way to the wall.

It would help to.extend the loft out to the middle point of the building so you had a central support making it 17' its always a tradeoff to have that big open cieling. I was watching a house.build the other day and i swear the ridge beam had to be 8" x 24" or more.

Quote from: Don_P on October 08, 2011, 08:33:39 PM
Interex, describe plan B, the load isn't going away, how are you thinking of building it?

Honestly, I'm not concerned with the load/weight of the building on the piers.  The piers held a 2x6 wall constructed 1 story 2330 sq ft double wide with no problems at all, granted I know it's not the same thing as what I'm doing, but the piers seem solid, the soil seems solid, and I really don't see anything sinking.  

So, I'm going to move away from the piers/soil concerns.  

I was wanting to run two beams down the center of the building, but since that 24' open span came into question, I am going to have to scrap that idea and just go with plain rafters and collar ties, like this....

(http://www.crodog.org/garage/ridge2.jpg)

That will work if the rafter ties are in the lower third of roof height, on every rafter pair, across the 24' open area. If you want ties higher in the ceiling then the situation is basically the same as what I described above. The ridge now becomes a beam and needs to be sized to support half the roof. If the high ties try to restrain the roof spreading forces they do 2 things. The joint forces connecting the tie to the rafter can become very large, beyond what nails can safely do over the course of time. Look at chapter 8 of the codebook in the rafter tables. Read the footnotes.Table R802.5.1(9) details the number of nails required in the connection and the footnote shows how much to increase thae nailing to account for raising the tie through the lower third of roof height. Second, the tie is causing the rafter to bend inward under load where the tie is connected. Instead of at one end where the bending stress is low in the rafter the tie is bending it right where it is weakest. Engineerable but this is why those scenarios step outside of the normal provisions of the code.

Trusses are another way of uniformly loading just the side walls and restraining the outward push of a roof. They do make them with a clear open ceiling.

Myself I would do the truss thing and let them worry about the engineering on the top part of the building.  Truss companies engineer for wind, snow and seismic where required.  Also if you still want the two beam look in the open area you could frame a couple faux beams in there.    

You could always do a hybrid.  Rafter Ties over the great room and Ridge beams for the shorter 8 ft loft area. 8 ft shouldn't be difficult to span with 2 - 2x8's or 2x10's.

Rafter ties have a few advantages.  From a practical framing standpoint, they can create a platform to work from, as in the picture you posted.  This can be a lot easier than scaffolding.  I know some who incorporate this into the design to hang things like lights or fans.  Also, if you are working completely alone, you can put the roof together one board at a time as opposed to renting a crane for ridge beams or trusses.

I got the floor done lastnight.

I need to trim around the outer edges to cut off overhang, but other than that it's pretty firm, and my 5' level shows we're level everywhere, but a few places have a little bounce to them so I'm going to crawl under and nail in some extra 2x8 pieces to "fudge" the joists where the floor isn't as firm as the rest.

Something I'm wondering about doing rafters with ties,  if I have a 10 foot wall, and my loft starts at 8 foot, and my roof is 16 foot from the floor, how low into the loft would the rafter ties be... and what kind of pitch would my roof have, being 24 foot wide?   I'm thinking 6/12 or so, but not too sure.



(http://i55.tinypic.com/2d2ac0m.jpg)

I don't understand why the floor feels spongy if everything from the ground up was sized correctly?   ???


Draw it out on a piece of paper using a scale. Use 1/4" per foot or whatever you can fit on the paper at hand. That's what I would be doing.  Remember when using rafters with a ridge board the rafter ties have to be in the lower third of the roof triangle.

(https://i139.photobucket.com/albums/q305/djmbucket/construction/framing.jpg)

Loft floor joists dropped down the wall don't qualify as a rafter tie. There are other methods like using factory built trusses.

How many rafter ties must there be, and what size should they be?

It appears I'm going to run into the same problem holding the outer walls in, as I would have with the roof beams.

One tie for each rafter according to current code.


What thickness floor sheathing?


On a wide building you may be getting into dangerous territory with a dropped floor loft at 8 ft on 10 ft high walls using standard rafters, especially considering the snow loads possible, as well as wind loading possible.

Rafter ties have to be in the lower third of the rafter.  So 10ft wall 16 foot ridge = 6 foot rise for the rafters.  6/3 = 2 feet.  So anywhere from 10 ft to 12 ft.  

Normally for loft areas people take different approaches.  They either go for a truss or ridge beam.  Trusses can be purchased or built.  I believe John has a home built truss design included with his 1.5 story plans.  Beam sizing we have covered.

Your roof pitch can be whatever you want.  The concept is, as force (wind, snow, weight of the materials) push down on the angled rafter, it pushes this force outward.  This pushes outward on the top of the wall, pushing your walls apart.  The rafter tie counteracts this by creating a triangle.

A ridge beam/wall supporting the rafter at the top and bottom stops outward force.

http://www.structural101.com/Structural-Ridge-Beam.html

Don, my floor sheathing is 3/4" Advantech T&G.

My loft floor has (will have) 4 posts coming up from the piers in the ground, plus the outer walls, and the loft floor would be used to tie the walls together at the loft, so I was thinking I could get by without having any rafter ties over the loft, and sticking with only collar ties.

As for the 24x24 foot span over the open area, I was just trying to figure out how to keep it looking nice and keeping a semi-open look to the top.... like a cathedrial style with 3 ties going across every 8 foot.

Maybe a look like this...

(http://lh5.ggpht.com/_19r4bBcvxdk/TDel-LW1z7I/AAAAAAAAFs8/tm0RoeKssPI/s640/IMG_0851.JPG)

(https://lh4.googleusercontent.com/-e6jGxdv6ipw/TbSoyyx4HkI/AAAAAAAAF2w/mS4iT6IwiWA/s800/IMG_1973.JPG)

(https://lh4.googleusercontent.com/-rXYAcFnKBPM/TbSpCemC37I/AAAAAAAAF28/NrlHFb0v1r0/s800/IMG_1976.JPG)

Quote from: interex on October 12, 2011, 12:20:00 PM
My loft floor has 4 posts coming up from the piers in the ground, plus the outer walls, and the loft floor would be used to tie the walls together at the loft, so I was thinking I could get by without having any rafter ties over the loft, and sticking with only collar ties.

Are you still going with ridge beams for the loft area?  If so, you don't need a rafter tie.  At least not below the ridge beams.  I'm not so sure about the 8 ft span above.  I am with MountainDon.  Your building is wider than many posted, including the one referenced.  Also note, in the build you referenced it says that if he had longer lumber, the rafters would have been lower into the room.

Quotes from that build:
" I have no experience in construction. I am doing a lot of reading and doing all the work from information I get from the Internet. "
"I used 16' lumber for my rafter ties if I had used 20' lumber it would be sitting right on top of my wall."

Many people on here, especially moderators will make recommendations based on generally accepted building design and code free of charge.  Some such as Don_P will go out of their way to give more advanced calculations and design people would generally have to pay an engineer for.  Some people just build things not in line with generally prescribed practices.  Sometimes it works, sometimes it doesn't.  You rarely hear about it when it doesn't.  I just wouldn't expect recommendations of methods outside of generally accepted principles of framing.

I could make my rafter ties come down lower (making them longer) if need be, as long as I could find a way to make use of 2 or 3 only and not 5-10 of them... I can have 20' rough cut log beams cut, or even make them myself.  We have several saw mills (lumber mills) in my area which I have contacted about pricing and sizing in the past.

I understand what you are saying about advice given, and structural codes... and the only thing I can think of is... those who give advice do so freely and I am reading what is said, just thinking that so much code is referenced, but it doesn't appear anyone here follows most of it.

I'm only showing pics of what I think looks nice and how I could go about doing my own build.

Also, I was planning to go with the 8 foot ridge beams over the loft.  I can easily make 2 3"x10" by 10 foot beams for over the loft.

Your plan for the loft area sounds like it would work.  Don_P could give more exact calculations, but I wouldn't be uncomfortable if I were in that position.  I believe two 2x10's would work if were a single ridge beam for 8 ft, since it is two beams, a true 3"x10" should be pretty close.  Why not just size up to a 4x10 if you are going to have a 4x4 post?

I try not speak to why other people went a different direction.  They could explain that.  Sometimes they can't.  They point to someone else on the internet as to why they did it, or misinterpreting a picture on the internet. I would disagree that most people don't follow most of the code.  Most people follow most of it.  Designing roofs seems to be one of the most confusing parts.  Some people don't look into the physics of how the load is transferred.  They follow a picture of how they perceive someone else has done something without knowing the why.  Over the past few years of frequenting the site, I have noticed a few things.  Many people built cabins and houses to John's plans.  They aren't overly complicated, but he spent a lot of time working out the calculations on sizing, load distribution, and design.  Other people could see the pictures, but not these details, so when they tried to copy this, they missed some of these details.  This leads me to the two most common areas of missed details that I noticed as being beam sizing on pier foundations and roof design.  There are many who use their loft floor to combat lateral force without rafter ties.  On smaller buildings, even though it is against code, it sometimes works, because the lateral load is smaller the thinner the building.  The wider you go the outward force can rise greatly.  You can see this in nailing requirements. I believe this was MountainDon's worry because your building width is wider than what most people build on here.

Now to what you are looking for.  I believe many of the origins of the design of larger rafter ties space farther apart were from timber framing and plank & beam framing of larger rafter ties spaced farther apart with thicker plank sheathing.
http://awc.org/pdf/wcd4.pdf
p.3 of the .pdf

I'm not saying it can't be done.  I know enough that there is always something I don't know.  I do know that it would be a more advanced framing and load technique.  If Don_P and MountainDon said to put it at every rafter pair, I don't know how many other people have that advanced knowledge to be able to help.  I assume it you did the rafter tie every 8', the rafter would have to be as large as possible. It would probably even be doubled or tripled with 2x T&G lumber roof sheathing or a plywood panel rated for an 8 foot span. 

Those that did follow the methods described.

Site built truss design.

(http://www.countryplans.com/images/mcelroy-1.jpg)

Both a Structural Ridgebeam and rafter ties combined.
(http://www.countryplans.com/images/amydan/fireplace.jpg)
http://www.countryplans.com/amydan.html

Site built truss design.
(http://www.countryplans.com/images/cowan-dorm.jpg)

Quote from: interex on October 12, 2011, 03:50:29 PM

I understand what you are saying about advice given, and structural codes... and the only thing I can think of is... those who give advice do so freely and I am reading what is said, just thinking that so much code is referenced, but it doesn't appear anyone here follows most of it.

1.  It's not fair to say that no one follows most of the code; many do, some may not. Codes also evolve; what was prescribed one or more versions ago may now be different and therefore some illustrated works may not be current.

2.  Read the line in the "News" section in the upper area of every CountryPlans Forum page:  
• Postings on this forum may or may not meet local building codes. Confirm structural questions with your inspector.

3.  Code is a prescription; build it as prescribed and it should be safe under the design conditions. There are other ways to achieve the end result in any construction detail; but to know that it is at least as strong as what is prescribed takes engineering knowledge and calculations, not simply casting an appraising glance at it and saying "hmmmm, that looks about right".

4. Read my signature line.

Best of luck.

5. Anyone can build in any manner they choose; future readers/viewers of all projects should reference numbers 2 and 5 above.

Don, I understand that very well.

As for the image below, I like how this is, and would like to achieve something similar to it.


(http://www.countryplans.com/images/amydan/fireplace.jpg)

I started this before dinner, the conversation has moved on, hopefully I'm not flogging a dead horse but there might be something of use, ignore the rest. I have an old post up on another forum that might help explain some of this. I'll need to move some pics and will post it in a little bit.

Squirl, that is not a truss, it is a rafter pair that has too high a tie. I know you didn't label it and I don't want to step on toes but calling a table a chair does not change what a thing is. Can it work? Maybe, but as either a truss or a high tied rafter it needs to be checked by a registered design pro. As the span increases the load goes up, also as the pitch lowers the thrust increases. Add it up and this puts the tie and its' connections into more tension.

I'm not sure where the problem was with the two purlins spanning the length of the room, that is a viable option. The loading would be a bit different than what I checked but it is quite do-able. In older timberframing one way to break that 24' long purlin beam span down further was to build one or more heavy timber trusses across the room and span the purlins across them with the common rafters supported by the purlins. This is one way large halls were spanned.

The ridgebeam option is also workable, obviously the load on one beam is going to be larger than the load on two purlin beams so the ridge would need to be larger. There is also a problem with foundation alignment below, that can be solved.

This is a picture of my current job. The room is 20' wide x 36' long. We installed heavy timber trusses that are really supporting a structural ridgebeam that in turn the common rafters hang from. Since my trusses are only about 6' apart a double 2x12 was adequate as a ridgebeam. The spacing was dictated by the architect's design, the trusses shown could have carried the roof at a greater spacing.
(https://i180.photobucket.com/albums/x109/windyhilll/Beyer8_15_11001.jpg)

(https://i180.photobucket.com/albums/x109/windyhilll/Beyer8_26_11012.jpg)

Using typical lightweight trusses spanning the width of the room the entire roof load is borne by the exterior walls. Something to consider with respect to the pier loadings. Do bear in mind the load never goes away, you do have control over how it is borne.

I think I'm seeing the thought that "since others here ignore building to code minimums, why shouldn't I". As far as I'm concerned you can build whatever you wish. What I try to point out is what is considered to be good construction, to our minimum standards. I often see owner builders venture outside of standard construction. This is fine but they are sometimes reinventing the square wheel out of a lack of knowledge of why things are done the way they typically are. Some are out there on the bleeding edge, there are some laws one simply cannot break, gravity comes to mind  :D. Some of the things I see done wrong may not show up at all for most houses most of the time, some may take years, some will only fail in a serious natural event. I do try to help those who are willing to help themselves but am nothing more than a carpenter. I try to steer you all in the direction of least bureacratic entanglement when we discuss design, that is why I reference the codebook's prescriptive design options whenever possible. When we step outside of that basic method of building the plan should really be checked by an engineer.

I've been working with a potential client and their designer and was writing an email
today. Seemed like alot of work not to bore someone else with it ..

I've attached some quick sketches of various ways to frame the greatroom roof.

These show a couple of approaches. I have a little example that helps
me explain how they work structurally.

Place a Christmas card on a smooth table, tent fashion. This is a
roof. Push down on the fold of the card, the ridge of our roof. The
feet of our roof slide out and it collapses. The vertical load travels
down the rafters and becomes a horizontal outward thrust when it gets
to the walls.

If you put some tape from side to side across the rafter feet and
repeat the experiment the roof will be stable. Notice a string or
piece of tape will work for that bottom chord, it is a tension member.
The 2 sides of the card, our rafters, are compression members. A
triangle is immutable, we have just built the simplest truss. If you
flattened the card you've ventured into strength of materials. In the
case of our greatroom trusses, the horizontal force, the tension in
the bottom chord is roughly 1000 lbs under a very full load. The
joinery at the rafter heeljoint needs to be capable of restraining
that force, the rafter, or top chord of the truss is trying to slide
off the bottom chord with a half ton of force, I have to hook it to
the bottom chord with a connection capable of restraining that. I've
drawn a birdsmouth that hooks the rafter feet down into the bottom
chord. This typically has an open mortise and tenon joint at the ridge

(https://i180.photobucket.com/albums/x109/windyhilll/tongueandforktruss.jpg)

Now look at the kingpost picture. A kingpost, the vertical member, is
sometimes called a kingrod in this orientation, its function is not
what it seems at first. It is not a post sitting on the bottom chord
and holding up the rafter tops.

(https://i180.photobucket.com/albums/x109/windyhilll/kingposttruss.jpg)

The kingpost is pinched between the top chords and hangs down to the
bottom chord. It is usually connected to the bottom chord and helps support
it from sagging. Think of it as a rope lashed around the rafter tops and slung
down under the bottom chord to hold it up. It is actually another tension
member. The reason we do not have to have one is that the greatroom span
is not so great that the bottom chords need help to prevent them from
sagging. We can add them as a decorative element but they do get into the
view from the loft rail.

(https://i180.photobucket.com/albums/x109/windyhilll/strucridge-1-1.jpg)

The third picture is a structural ridge. Go back to our Christmas
card. With no ties and pushing down on the fold we know it has
unrestrained thrust. Now put a pencil under the fold and support each
end on books. Push down on the ridge and there is no thrust. If we
support the ridge on a heavy beam and hang the rafters from that then
we need no ties, there is no thrust. I drew it with a 7x12 glulam
ridge and 4x8 rafters on 4' centers. The ridge beam is supported by a post
at the far end, we would support the near end in a heavy steel hanger
attached to a beam in the loft wall.

Those are nice looking timber trusses and could be used to get the open beam effect shown in the earlier photo. They would likely require an engineering workup to meet the local snow and wind loads.

I'm one of many members who appreciate the posts of Don_P and all the building information and experience he has shared on this forum. He doesn't play building inspector, but he does have a good understanding of buildings and how the construction of them has evolved.

Not all the houses posted on this site have followed all the elements of all the code requirements. When you build your own house, especially in a non-code area, you have choices and options. Build responsibly - forum members like Don will try to help you do that.

While I don't post much on this site, I do try to visit every few days and see how everyone's projects are progressing.

It amazes me that there are people here daily (like Don_P, John Raabe, Glenn K, MountainDon, and many others) who freely donate many hours of their time, and offer their suggestions & advice to others who are trying to accomplish a project. 

I sincerely hope everyone appreciates this "free" knowledge, and the ability of these folks to articulate their knowledge in a helpful & professional tone ... never condescending or critical for the sake of being negative.  These folks are true professionals, their knowledge is spot on, and in my humble opinion, this website is without equal.

Quote from: PA-Builder on October 12, 2011, 09:29:10 PM
While I don't post much on this site, I do try to visit every few days and see how everyone's projects are progressing.

It amazes me that there are people here daily (like Don_P, John Raabe, Glenn K, MountainDon, and many others) who freely donate many hours of their time, and offer their suggestions & advice to others who are trying to accomplish a project. 

I sincerely hope everyone appreciates this "free" knowledge, and the ability of these folks to articulate their knowledge in a helpful & professional tone ... never condescending or critical for the sake of being negative.  These folks are true professionals, their knowledge is spot on, and in my humble opinion, this website is without equal.

^^ What he said... Round of applause! :)

I can't thank them enough.  They have both taught me to fish and given me a few. (figuratively)

I thought you would have been interested in the second picture.  That is why I left the link below it.

(https://i31.photobucket.com/albums/c371/casonjimmy/7b39re2.jpg)

You can see the very large structural ridge beam.  It looks to be supported by the stone fireplace.

So Don, how do you size those timber frame trusses?

Sorry about the nomenclature on the trusses.

Don't get me wrong, I appreciate everyone's responses, they are a great deal of help and guidance.

I do like it, very much so, but the problem comes in with the 24 foot span and the beams needed to handle the weight. I can't see myself spending $800 or more per beam or tie, for veneer or lamented wood.

Quote from: interex on October 13, 2011, 12:19:04 AM
I can't see myself spending $800 or more per beam or tie, for veneer or lamented wood.

Quote from: interex on October 13, 2011, 12:19:04 AM
Don't get me wrong, I appreciate everyone's responses, they are a great deal of help and guidance.

I do like it, very much so, but the problem comes in with the 24 foot span and the beams needed to handle the weight. I can't see myself spending $800 or more per beam or tie, for veneer or lamented wood.

That is the cost of having the wide open room.  You could alleviate almost all of the concerns by adding posts and cutting down the 24' span.  IIRC you have foundation piers every 8 ft.  Two extra posts would cut the 24 ft down to 16 ft, which by my reading and some of Don's calculations could be spanned by dimensional lumber.  It would  be a pretty cheap fix too.  I have seen many people incorporate these posts into the cabin feel by using trees with the bark peeled off.

You are lucky.  You are in a 20 lb snow load area.  I'm in a 50 lb snow load area.

Adding posts in the middle of the room doesn't look too appealing to me.

I like the rafter tie idea most, and if I can do it at every 8 foot, so that our weight is more in line with the piers below, I think this is the route I will take in the open room area.

I am going to contact an engineer to find out how big of a tie I will need, and if I can make it from 2x10s or 2x12s with plywood/glue/nails... and how high up the rafter I can safely go to keep me from having a 24 foot beam resting on the 10 foot walls.

I greatly appreciate all the responses and opinions, just trying to see what I can do and still make it look nice, and keep things sturdy.

  I looked into the cost of a 24' parrallel scissors trusses to handle this vary issue.
  I discoverd that the cost difference was not vary great when you priced out the ridge beam and #2 fir 2x12's long enough to span the 24' room.
  I could not set the trusses myself so I would need to hire a framing contractor to set them.
  You can look at rdzone's build (Finally Pictures of our 20'X30' 2 Story) and look at page 8 and see them.
  Your local building supply will do all the engineering for you as part of the deal. I found out this was going to be fairly easy to get approved by the building inspector.
  In the long run I concluded that the cost of the cathedral ceiling was more than it was worth to me.

Don P,

Thanks for taking the time to explain this.  Your Christmas card illustration and Sketch Up examples really helped explain the forces at work, and why and how various methods are used to accomodate them. 

Don... great post/pics/example! that was very easy to follow and very helpful.

Y'all are quite welcome, thanks for the kind words.
Now for the humble pie  d*. I've redrawn the structural ridge pic above to make it more clear. I placed the ridge under the rafters and drew a level seat cut at the bottoms of the rafters.

I would like to see what your engineer comes up with interex. I doubt one would design this site unseen but do make sure they visit the jobsite so they can check the entire load path.