OK So I built the floor and decided to leave it as a 6" floor -- it's a cabin right? -- and then began to frame my 2x6x10 walls and suddenly thought: Is this floor strong enough for such heavy walls?
Thoughts? Am I making a mistake?
Please post a picture of where you are at. That will give us all a better idea of the situation.
Words only go so far...
I ask because I'm wondering if you are doing the Little House lightweight foundation where the walls rest on cantilevered joists... That foundation was not designed for a full two story load or heavy wind or snow. The Builders Cottage plans from the Enchilada plans are better suited to such conditions.
(https://i998.photobucket.com/albums/af102/emcvay/Cabin-1stwall.jpg)
(https://i998.photobucket.com/albums/af102/emcvay/Cabin-2ndwall.jpg)
Not sure if those show well enough.
I have two walls up so far and just wondered if I was building too heavy of walls for the floor?
The wow in the wall stud by the way is an optical illusion! Each time I see this picture I cringe! hehe
So to recap: 4x8 beam made of 2 2x8's nailed and glued with a 1/2 ply between them (with proper overlaps), 2x6 framed floor and 2x6x10 walls all based on the 14x24 plans (Builder I beleive it's called)...with lofts etc.
I was just wondering if my walls made the cabin too heavy for 2x6 floor joists?
The silence is deafening...
I was thinking I might go with 2x8 floor joists but then figured this is a cabin in the woods and if the 2x6 floor would be strong enough then why change it? Now I'm just wondering what kind of load those 2x6 joists can take?
They are on 16" centers and span the beams as per the plans....so I'm hopeful it's fine -- just don't want the floor to shear the joists and become 'shorter' some day!
Hind site right?
OK, I've been reading as much as I can and I think I might have the answer:
It's fine.
Why? It seems the real concern isn't the depth of the joist for load bearing but span and load bearing over the span. Am I right?
In other words you need to span no more then 9'9" for DF#2 2x6 becuase that's max for 40lbs per foot of load right? So the span maximum is set to prevent the floor from bowing, buckling etc and not becuase of any sheer potential.
The sheer potential and bending potential of the joist is another concern of course but I suspect that becuase these joists are 2'2" from the center of the beam and have 3/4" OSB flooring on them their overall strength is much greater then a single boards strength. So they should carry the heavier 2x6x10 wall without major issue -- or I'm assuming anyway.
I suppose if it is cutting it close though, I could add an additional beam the length of the floor out near the edge of the deck thus creating an even stronger foundation?
Also, I plan to put a deck off the main floor using posts and piers so perhaps I'll just need to consider that...
Quote from: OlJarhead on October 13, 2009, 10:04:45 AM
The silence is deafening...
I've been silent because I don't have an answer backed by calculations.
John's plan does show 2x6 floor joists on 16" centers. The difference is that you have used 2x6 for wall studs instead of the 2x4 indicated in the plans. Plus your walls are taller. I imagine the roof will be much the same as on the plans so there's no additional weight there?
So, I'm thinking, guessing, that the floor joists probably have enough safety factor incorporated into the design to be able to handle the extra weight of the taller 2x6 wall studs, plus the additional wall sheathing. But that's a guess, nothing more, nothing less. 8)
Ah, yes... just checking back on this. You are putting extra weight on the cantilever at the joists. I agree with Don that I think you are within the safety factor (about 8x for DF according to Charlie Wing). For all species the safety factor varies from a low of over 7 to over 9.
However, I am not a sophisticated enough engineer (I'm not an engineer at all) to be able to check your specific situation. In this case for shear on the extension of the joists.
If you wanted to be cautious without having it checked by a local engineer you could add a 4' 2x4 to every other joist. That would increase the section modulus (beef) of the joist
Quote from: John Raabe on October 13, 2009, 11:10:31 AM
Ah, yes... just checking back on this. Let me do some calcs and check this out. You are putting extra weight on the cantilever. What is your snow situation? Are you doing the steep pitch (12:12) roof?
12:12 roof per plans -- I considered doing 2x8 roof rafters and would like to....hadn't thought of the weight I'm adding.
Snow load? Depends on Global Warming I guess...except that it was 5 degrees Saturday morning and I predicted we could see a 30 year cooling trend now....so, bearing that in mind (*chuckle*) I just read that:
Quoteminimum roof load of 40lb will stand up to the snow load in most areas of Okanogan County, however if you are placing the home at higher elevations that get more snow you may need to order your home with a heaver roof load rating.
(https://i56.photobucket.com/albums/g166/jraabe/cant-joist.jpg)
Here's one idea.
Another stiffener would be to angle a short 2x6 brace from the rim joist to the beam. Nail it to the joists. Might be easier.
(https://i56.photobucket.com/albums/g166/jraabe/cant-joist2.jpg)
Quote from: John Raabe on October 13, 2009, 12:08:30 PM
(https://i56.photobucket.com/albums/g166/jraabe/cant-joist.jpg)
Here's one idea.
Nail a 2x4 to each joist under the wall and extending over the beam? Never thought of that but it certainly would add to the shear and bend factors right?
One thing I'm wondering is how much difference does the deck make? I'm figuring on putting hangers on the rim joists and then 4' out a beam on post and peirs using PT 2x6 for the flooring just like the cabin floor.
My question is: does this change anything?
Snow load: What type of roofing material? A steep pitch metal roof will not accumulate much snow before it slides off. Shingles will accumulate some before it slips off.
Deck: with a roof? I think a row of posts and a beam at the cabin wall to support the deck without placing additional loads on the cabin structure might be a good idea.
I'm with Don. Let's not add more weight to the cantilevered wall and floor joists. Make the deck self supporting.
Quote from: OlJarhead on October 13, 2009, 11:30:30 AM
12:12 roof per plans -- I considered doing 2x8 roof rafters and would like to....hadn't thought of the weight I'm adding.
2x6 rafters will be more than adequate when on 16" centers. Of course 2x8 would allow for more insulation in a cathedral ceiling.
Tin roof -- and if 2x6 will do then we'll go with that! Save the weight/loads!
Like the idea on the deck too thanks!
Just re-read this again -- cool!
I've got lots of information here so I think I'm good. I'll do a little of both perhaps (going to borrow an air nailer to assist).
Thanks again for your replies!
Getting ready to go back and get the walls done and try to complete the roof!
The weather is supposed to be cold and rainy/snowy but I'm hopeful it isn't too much!
Quote from: MountainDon on October 13, 2009, 12:24:10 PM
Quote from: OlJarhead on October 13, 2009, 11:30:30 AM
12:12 roof per plans -- I considered doing 2x8 roof rafters and would like to....hadn't thought of the weight I'm adding.
2x6 rafters will be more than adequate when on 16" centers. Of course 2x8 would allow for more insulation in a cathedral ceiling.
Just re-read this thread (looking for something else) and saw this post....how did I miss this? :( I went with 2x6 rafters on 24" centers.
Of course the 12x12 pitch means no snow load and 6 months of being installed (without all collar ties) and the roof seems to be holding just fine.
I'm hopeful that this cabin doesn't start to sag on me in the near future but I'm thinking it will be ok -- I once had to peel the sheeting off someones roof (after removing roofing) and 'shim' the sheeting with wedges cut to the sagging rafters to clean up the roof line for a customer.
I'd advised them that they needed to replace the rafters and put a new roof on but they weren't interested, they just wanted the roof of the old house to match the new carport roof I'd built for them (with trusses) so I complied with their wishes. Their rafters were 2x4's! But after 35-40 years they were still hanging in there though I anticipate their collapse some day (to that note we did add a little extra bracing here and there to try to shore of the ridge beam and rafters but their roof is doomed sooner or later).
Anyway, I'm finding I've forgotten more then I imagined possible and have rushed past the rest in the attempt to avoid weather :(
Note to self: slow down, do it right and forget the weather.
Be sure to get the collar ties in place as they will stiffen the rafters, triangulate the forces and cut down the working span. Also spend some time reinforcing the connection between the rafters and the wall. Use a metal framing anchor or strap.
Do that and you should be fine.
Quote from: John Raabe on June 03, 2010, 01:06:41 PM
Be sure to get the collar ties in place as they will stiffen the rafters, triangulate the forces and cut down the working span. Also spend some time reinforcing the connection between the rafters and the wall. Use a metal framing anchor or strap.
Thanks John.
I used Hurricane ties on the walls to the rafters though with my installation (rafters) being so tight I couldn't get them inserted up the wall to the rafter so I had to lay them on top of the walls and push into the rafter. Which, when I think about it might even be better -- or at least exceptable.
I plan to get collar ties on this weekend as well as additional blocking etc.
Also have to work on the foundation as one beam is bowed a little as if one pier raised up or two outside piers have sunk.
Anyway, my plan is to install a post and pier at each end of the 24' beam (the kind of block with the bolt saddle that you can ajust height with - to tighten into the beam). I'm thinking this will add additional support.
https://i290.photobucket.com/albums/ll257/loonlakebound/DSCF1310.jpg
I wanted to revisit this thread with a question:
Why could I not go ahead and nail 2x4s to the inside of my 2x6 rafters using this method (plywood/osb sheeting to tie them together)?
To clarify something: I went with the 2x6 rafters after much debate because of the cantilever floor and 6" walls. I was worried that I had too much weight on the cantilever. However after much consideration I've realized that I can solve that problem when I build my deck :) All I really have to do, correct me if I'm wrong, is put a nice heavy beam (say 4x6) down the length of the cabin under the cantilever and jack it up to the floor -- then I can hang the porch off the beam with joist hangers. This has the added benefit of removing the cantilever as well as eliminating the need to separately frame the inside wall of the surround deck (something we figured would be wise because of the cantilever).
Bear in mind that once my LT10 arrives I'll be able to mill my own 4x6 beams (I have a Fir I'm eying now) for this so cost won't be an issue (which it was previously).
Why would I want to do this? I just don't like the options for insulating my roof now and really wanted more then the R19 I'm likely to get now and by doing this I also eliminate the shelf on top of the wall as well as better tie the roof into the walls.
I'm still just pondering this and if I'm insane in thinking I need to do any of this please smack me back to reality! It's just something I've been thinking about for a long time now and I kinda thought I had the answer now :P
Quote from: OlJarhead on January 20, 2011, 01:55:38 PM
https://i290.photobucket.com/albums/ll257/loonlakebound/DSCF1310.jpg
Why could I not go ahead and nail 2x4s to the inside of my 2x6 rafters using this method (plywood/osb sheeting to tie them together)?
The biggest difference between your roof and the other roof is you used a ridge board and the other ses hand built trusses. The peak has a sandwich around the rafter points/tips made from plywood. I believe John's 20' wide has an option for owner built trusses and those were engineered if I'm correct. But they are much the same as what is used in that image you selected. Something like that, to increase the space for insulation, should work I think. The plates would be better if plywood rather than OSB I believe. Waterproof glue should be used as well as a well developed nail pattern. Would you redo the cross ties you have as well?
The beam under the side... I'm not clear on what would be supporting it and if you mean it would be under the existing main cabin side wall. I think that is what you mean and you'd have a set of posts to support it. Then you would ledger off that. ???
I think what OJ is suggesting is to put this new beam under the house side of the deck thus taking the load off the house foundation and sidewall. This is a good idea and will also allow for good flashing to keep water from the deck side getting into the house wall and floor. When the deck needs to be rebuilt (and it will age faster than other parts of the project) this will be a stand alone project.
But... use something more substantial than a 4x6, you've got a mill, that dimension is trim.
There was a previous comment in this thread that wood is 7 to 9 times stronger than the allowable design strength. This is kind of misleading. Grading shoots for 95% of pieces being at least 2.1 times design value and 5% of pieces are allowed to be between design value and the 2.1x safety margin. There may indeed be a few pieces in the pack that are many times stronger than the allowable strength rating... but it would not be a good idea for the novice to count on it.
Quote from: John Raabe on January 21, 2011, 04:16:00 PM
I think what OJ is suggesting is to put this new beam under the house side of the deck thus taking the load off the house foundation and sidewall. This is a good idea and will also allow for good flashing to keep water from the deck side getting into the house wall and floor. When the deck needs to be rebuilt (and it will age faster than other parts of the project) this will be a stand alone project.
Yes, thereby changing from two supporting beams underneath to 4. The last two right at the outer edge and under the floor directly under the wall -- using pier blocks with the 'jack' type cradles the beam could be jacked right up under the floor. I did this for wood stove support actually.
This would leave a nice beam to hang the deck off of also -- and as you mentioned, it will facility an easy rebuild of the deck in time.
DonP: I think you're saying mill a 4x8 instead? That would make a 4x8 at the outside walls (load baring) as well as on 9 foot centers under the floor.
Jarhead, in white pine the log home companies would send a 6x8 is a porch roof carrying beam that can support about 8' of roof at 8' post spacing, floors require more beam than that. I've rarely been able to get enough info to size parts here, look at the girder tables in the deck guide or code book and go bigger for solid sawn timbers. If you've got a mill you can make real timbers, don't think small, use the tree ;).
... unless he's got trees like me. :( The ones that would make good 8+" beams are those we want to keep.
The trees I'm sawing next weekend average around 16" in diameter over 8 feet...I have some that are about 18-20 at chest height. However I have some I need to drop that are about 60 feet tall and probably over 14 inches above 30 feet!
Not sure if I mentioned it earlier but I'm buying a woodmizer Lt10 in the neat future if all goes well :)
As I understand what you are proposing; When you jack up and support the cabin on a beam under the wall, the weight of the main floor half the distance to the existing beam, the wall, half the upper floor and half the roof will bear on the beam, as will half the deck load. For myself, I'd count on a future porch roof as well.
This is BTW a good plan, I'm just trying to smack you into dimensional reality.
My beam and column calcs are here;
http://windyhilllogworks.com/Calcs/beamindex.html
You are probably looking at using the top, simple beam, calc. If you can give me the species you are going to be using I'll give you the design strengths to plug in.
A bandmill will make shorter work than the chainsaw mill, the lt10 is a hobby sized mill. I saw where you were talking about a sideline business with it, you'll rethink that pretty quickly with that mill. Also look at the Norwood, a local retiree is doing a pretty good sideline biz with his. Find an ag show or similar where you can watch or play with them all.
This is a shot at the end of the day today, we've begun playing with the timbers on the job. These are 6x8 beams and 6x6 posts. Simplifying the layout a bit, there will be a floor above, joists spanning about 15' from the window to the beams, the posts are about 6' apart there is no floor on this side bearing on the beams. They are pretty much maxxed in white pine with just the upper floor load.
(https://i180.photobucket.com/albums/x109/windyhilll/beyerbams122003.jpg)
The mountain of rocks outside the front is some of what we've gathered from the field edge piles, the mason is using them for porch walls [cool]
Thanks Don.
My intent is to continue to use the original beams also thus having 4 beams rather then two. The initial two are in accordance with the plans at ~9' apart (I'll have to check exactly but I think it's 9' on the nose on center) so the next two would be under the outer walls about 13'6" on center.
Yes, the load path shifts, think about what I described and it should make sense.
The 4x8 beams in the lightweight 14x24 plan (from the Little House plans kit, not the 14x24 Builder's cottage which has a perimeter concrete foundation and engineered I-joists) are only spanning 4' - there are 6 piers on each side under the beams and the floor joists span a bit over 9' between the beams. In the first photo you posted it looks like that is what you have built.
In the first page of this thread I think we decided you should not be adding new weight to this foundation and that the deck should be free standing and not adding to the wall load with hangers. If I understand what you are suggesting, you plan to use much the same foundation plan for your deck as you used for the house?
Decks should be designed to carry even more load than house floors (typically 60 psf rather than 40) because they can have very heavy loads during a party or such. Not that there aren't thousands of existing decks that are built less strong than house floors - there are. Usually this will not be a problem if lightly used. But a failure, especially when the deck is high in the air and loaded with a bouncing crowd at a party, can be devastating.
Quote from: John Raabe on January 24, 2011, 04:10:36 PM
The 4x8 beams in the lightweight 14x24 plan (from the Little House plans kit, not the 14x24 Builder's cottage which has a perimeter concrete foundation and engineered I-joists) are only spanning 4' - there are 6 piers on each side under the beams and the floor joists span a bit over 9' between the beams. In the first photo you posted it looks like that is what you have built.
In the first page of this thread I think we decided you should not be adding new weight to this foundation and that the deck should be free standing and not adding to the wall load with hangers. If I understand what you are suggesting, you plan to use much the same foundation plan for your deck as you used for the house?
Decks should be designed to carry even more load than house floors (typically 60 psf rather than 40) because they can have very heavy loads during a party or such. Not that there aren't thousands of existing decks that are built less strong than house floors - there are. Usually this will not be a problem if lightly used. But a failure, especially when the deck is high in the air and loaded with a bouncing crowd at a party, can be devastating.
I'll have to go back to the beginning of the thread but this sounds correct, which is why I decided to increase the strength of the foundation itself. My thinking was that 4 beams supported as you stated (on 4 inch centers) would be twice as strong as two. However, if i understand DonP correctly then in reality the new beams would really be taking the load leaving the old beams to take only the load in the center of the house -- which is ok.
So, if that's correct I'll be looking at heavier beams which I'll toss into DonP's calculator to see how well they work...so maybe some 4x10s to start -- and of course since they would be Pine they might need to be heavier still. But I have LOTS of tall pines :)
Just need to order an extension bed for the LT10 when I get to ordering :D
If you are putting new beams under the wall line and parallel to the beams about 2' inside the walls, then yes - those new beams will be carrying a bit of the main floor load (about 1' wide) and all of the wall, plus 1/2 the roof and loft loads. The existing beams will now support most of the main level floor loads. This would be a good way to carry the taller 6" walls and the extra weight of a loft.
Quote from: John Raabe on January 25, 2011, 03:07:59 PM
If you are putting new beams under the wall line and parallel to the beams about 2' inside the walls, then yes - those new beams will be carrying a bit of the main floor load (about 1' wide) and all of the wall, plus 1/2 the roof and loft loads. The existing beams will now support most of the main level floor loads. This would be a good way to carry the taller 6" walls and the extra weight of a loft.
That's the plan :) Kinda feels good to have one!
You got it ;)
I am going to resurrect this topic:
If I beefed up the entire floor could I build what oljarhead has built? larger beam than 4x8, and larger 2x8's or 2x10 floor joists?
Could you describe what it is you want to build; L x W x height, # of floors and so on? That would probably result in a better, more accurate and clear answer. We'd have to re read what OJH has done anyway, at least I would as I don't remember all the details of his project.
New topic of your own would be fine too. :)
ok, I am trying to build something relatively small, something between OJH 14x24, or rick's in vermont 10x16. I am thinking 12x18 or 12x20 with 10 foot sidewalls to have a sleeping area upstairs big enough to put in a real bed, even if not on a real bed frame. I am in the UP of MI where there is a considerable amt. of snowloading. I want a 12/12 pitch roof (metal). I have come to find that the ground is a crummy loamy soil, not good for much. most neighbors have very old cottages on slabs built on/ or built up off grade, not dug down below. I am thinking that if I use a shallow base, foundation piers, or dig down 3feet or so and backfill with gravel and then put these pirs on top that will eliminate frost heaving. I am not sure if burying 4x4's in this loamy soil is a good idea, like rich in vermont did. I have asked about beefing up the foundation to have the taller walls, I dont need the beams cantilevered, I can run the beams all the way to the edges if need be. This is why I am asking about beefing up the original little house plans (12x18 or 12x20)
Dreamer:
I think your suggestion of getting down 3' (I assume this is below frost depth) and building a crushed rock footing is good. You could do concrete tube or block piers or 6x6 foundation grade PT posts (see this article (http://countryplans.com/foundation/index.html)). Brace these piers to sturdy built-up beams and use 2x8 or 2x10 joists @ 16" o/c for your floor (assuming a 12' span). You should be good to go on your platform.
What size should the beams be, or is what is listed in the little house plans good enough?
They would need to be deeper than the Little House design since you have more loft load if I understand correctly. To be accurate you should do a load trace and consider the snow loads as well. Don_P has some links to beam calculators (http://theownerbuiltcabin.com/)if you want to do this yourself. If you just want to have plenty of beef you could use built-up beams of 3 laminated 2x10's. If you are using 6x6 posts you could shim out this 4.5" wide beam with a couple of 1/2" ply shims to fit a 6" saddle for the pier to beam connection. You can then bolt in 4x6 braces between beam and post.
Does it matter if those spacers for the beam are plywood, or just cut from a 1 x 10? Other references to this technique also mention plywood. Thanks.
Those spacers add little to the strength of the beam and don't have to be continuous for the length of the beam. In other words you can just use small pieces of what ever thickness needed to fill the open space at the brackets. You run your screws or nails through these spacers and into the beam.
I was typing and interrupted myself :D
So, I ditto what John just said. The plywood or whatever is simple spacing material. Strength of the beam is calculated on the lumber used and that's it. Place any splices in the dimensional lumber over the supports.