24x32 in Southern Illinois - New member.

[interex]

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.

[interex]

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

[MushCreek]

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.

[interex]

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.

[interex]

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.

[Squirl]

Welcome.  

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.

[interex]

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.

[Texas Tornado]

How about a picture showing what you are saying?

[interex]

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

[Squirl]

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.

[interex]

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...

[interex]

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.

[Squirl]

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?

[interex]

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.

[dug]

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.

[interex]

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.

[Squirl]

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.

[interex]

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?

[Squirl]

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?

[interex]

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.

[dug]

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.

[Texas Tornado]

Even with tie downs mobile homes can flip.

[interex]

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!

[interex]

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.

[Don_P]

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.