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Zukowski
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# Posted: 23 Aug 2016 15:12 - Edited by: Zukowski
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Can someone tell me how this cabin was built without a ridge beam? http://www.countryplans.com/lemay.html
They are in a similar climate but maybe have a smaller snow load. I like this cabin and and want to do one 18x24 thats pretty similar but if i use a ridge beam I need to have a post that will take up floor space.
I see they use collar ties but from what ive been told on here thats not enough to stop the walls from spreading. The only other thing i can think of is the loft beams they use, those should hold the walls together but is it right?
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Steve_S
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# Posted: 23 Aug 2016 17:25
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Ridge Board is all you would need for something that small and no beam to foundation in centre either. A Ridge Beam is a different animal... this is very commonly intermixed.
If using 2x6 Rafter's, 2x8 Ridge board... 2x8 rafter's, 2x10 Ridge board.
Mine is 2x8 rafter with 2x10 ridge board spanning 28' length (2' each end sticking out for gables).
As for 2x4... I'd suggest 2x6 structure. 2x4 has gotten so cruddy in the past few years, knotty and very young wood... nothing like what was.
Ridgeboard with Simpson Rafter Ties and collar ties = strong.
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curt
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# Posted: 23 Aug 2016 20:06
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Shouldn't need ridge beam. Here is my 16x28.
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MtnDon
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# Posted: 23 Aug 2016 20:47
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Quoting: Zukowski The only other thing i can think of is the loft beams they use, those should hold the walls together but is it right?
Brief comment...
1. Just because someone built it does not mean it is good design. Just because there are many built in a similar fashion still does not make it good design.
2. Yes, the way they used loft beams does lend some resistance to outward rafter forces on the walls... but it is still not good design. The horizontal rafter force is pushing out on the stubs of wall studs that rise above the loft floor level. Studs are not meant to receive those forces.
You are correct in understanding that collar ties do nothing to prevent wall top spread. Collar ties tie the rafter tops together, to keep high winds from peeling the roof apart. A totally different purpose. Collar ties should be in the top 1/3 of the rafter triangle to be effective for that purpose. Higher up the better. Sounds like you probably have read that already.
3. Rafter ties should be in the lower 1/3 of that rafter triangle or they should do triple duty as ceiling joists for the lower floor, floor joists for the upper floor and be placed on top of the wall studs. That way they also act as rafter ties.
4. If that does not provide enough loft headroom consider (A) a ridge beam with proper supports down through to the foundation. (B) Build the loft as I described and use short walls and rafters, with the rafter ties located no higher than the upper limit of 1/3 the way up. You might need (guessing) 4 or 5 foot high sidewalls up there to achieve that. Try paper and pencil or sketchup. That might result in a building tall enough to present too much sidewall to high winds for the width.
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bldginsp
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# Posted: 23 Aug 2016 23:23 - Edited by: bldginsp
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Looks downright dangerous to me if it had a heavy snow load on it. Even if it never does, I bet it gradually sags.
Here's one approach to the problem
Darn- can't get photos to download...
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sparky30_06
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# Posted: 24 Aug 2016 06:53
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One thing to remember is that your roof pitch will be governed on your snow load. Down here in Texas I can get away with a 1-12 pitch on a metal roof with some small framing lumber. Now take me up to the UP of Michigan ( I miss snowmobiling up there!) and I would build a 12-12 or greater pitch to get that snow gone & with some larger framing. That is why we have codes, they are a pain and I dealt with them for almost 20 years, BUT some of them are good. You can find out what size lumber to use with what pitch on your roof once you know your load. Luck for us cabin and shack builders we don't have to worry about roof top AC & Heat units or a homeowner wanting to put a deck with hot tub on their roof.
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bldginsp
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# Posted: 24 Aug 2016 08:38
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All that you said is true sparky, but at the same time the basic design of this structure isn't stable. The only things preventing the walls from being pushed out are the collar ties (nil), the end walls (fine for the end walls, nothing much for the roof center), and the attachment of the loft floor/ledger/beams (which, if nails, will pull out). The building simply has poor geometry, and can fail as a result.
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treetech
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# Posted: 24 Aug 2016 08:58
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What if they went with a full loft and had floor joists connecting to each stud? would that provide enough support for the stubs?
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MtnDon
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# Posted: 24 Aug 2016 09:31
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No.
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bldginsp
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# Posted: 24 Aug 2016 12:59
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What that would do is make a 5 sided polygon, rather than a triangle (as with ceiling joist rafter ties. A triangle is stable, a 5 sided polygon is not. Maybe an engineer could make it work with special connectors etc, but that's expensive.
If you are building a simple building, build it simply.
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Zukowski
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# Posted: 28 Aug 2016 03:50
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Thanks everyone for the information, sorry my reply is late but tech school started up again and has taken my attention.
I really like the loft and open ceiling layout so I'm going to design something with a ridge beam. If I do 10 foot walls with a 8/12 pitch that gives me a height of 16 feet. With 2x6 walls I can't go 16 feet up with balloon framing. Will I be able to platform frame that then?
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