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entertreestand
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# Posted: 23 Mar 2014 18:05
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Ok so I think Ive finally decided what I want. My plan is a 12x16 stick built cabin. Im thinking about putting it on skids so I can move it but I havnt yet decided. I was thinking of using 2x12s on all my outside boards of the foundation and then using 2x8s 16"oc. Would I need a support down the middle or would that be a good span? All of this wood would be pressure treated. Would my sub floor need to be treated? It would be 3/4 inch thick. 2x6 walls also 16" oc packed full of insulation. I was thinking a 8-10x12 loft. Id like to have a functional bath and kitchen. Figured id have a 12/12 pitch to get the most head room in the loft. This is all I can think of right now but hows my plan sound?
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bldginsp
Member
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# Posted: 23 Mar 2014 19:10 - Edited by: bldginsp
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Sounds good. One way or the other, make sure air can flow underneath so you don't get moisture build up. Span issues in buildings this small are not crucial unless you get a lot of snow, and with a 12/12 pitch you'll lose the snow quickly. Your 2x8 floor joists will be fine at 12 feet, if not quite to code tables (which are a bit overkill anyway. I think a major pitfall in these small cabins is the issue of ventilating a vaulted ceiling. Big potential for mold, if you heat the space in a cold climate. You thought about this one?
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entertreestand
Member
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# Posted: 23 Mar 2014 19:17
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I live in Michigan right around the thumb area so we do experience a good bit of snow in the winter and sometimes pretty cold temps. Planned on wood heat inside and windows at each end of the house at the peak. if I insulated the floor and sheathed underneath would I have moisture problems? another thing that really confuses me is vapor barriers. where and how should they be installed in a small cabin like this in Michigan??
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bldginsp
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# Posted: 23 Mar 2014 19:27 - Edited by: bldginsp
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The basic problem is that warm air holds more moisture than cold air, so when warm moist air from inside the cabin contacts a cold surface, like the roof plywood underside, the moisture condenses, it gets wet, and if there's no way for it to get out mold forms. Moisture barriers are supposed to keep the moisture from the interior air from getting to where it could condense, but they only slow the rate of moisture transfer, not stop it altogether. It's usually in ceilings where the problem is most pronounced, but if you put plywood on the bottom of your floor joists, below insulation, you could trap moisture. So, the place to put the moisture barrier in that scenario is on top of the floor joists before the plywood, I guess. But no one does that ever here in California. Vaulted, insulated, unventilated ceilings are where the worst problem is. You can put a moisture barrier on the rafter undersides, and or ventilate above the insulation, or use spray foam insulation. Or, instal ceiling joists and have a ventilated attic, but there goes your loft.
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entertreestand
Member
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# Posted: 23 Mar 2014 19:44
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I would ventilate every rafter joist with attic vent and also have full ridge vent and soffit.
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bldginsp
Member
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# Posted: 23 Mar 2014 19:49
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That's the best way to go, I think. Get good cross ventilation across the top of the insulation. Then, even if the moisture gets there, it has a way out
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entertreestand
Member
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# Posted: 23 Mar 2014 22:22
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I agree. Ill put them in each roof joist cavity soffit-ridge cap. It will give me good ventilation up and down each joist and across them all.
Any more tips and tricks would be greatly appreciated
Thanks Kyle.
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bldginsp
Member
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# Posted: 23 Mar 2014 22:27
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They make these plastic pans for the purpose- they go up in the joist bay against the plywood, and keep the fiberglass insulation from hitting the plywood. You should keep 1 inch space above the insulation. If you use rigid foam, you don't need the pans. Rigid is a lot more expensive but gives you a lot more R value per inch thickness.
Send pics!
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entertreestand
Member
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# Posted: 24 Mar 2014 11:37
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Is this what you're referring to?
http://www.menards.com/main/building-materials/insulation/accessories/provent-48-plas tic-attic-vent-chute/p-137193-c-5776.htm
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bldginsp
Member
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# Posted: 24 Mar 2014 14:03
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Exactly, there are various brands, its just a sheet of molded plastic, I think I've seen them cheaper
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Just
Member
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# Posted: 24 Mar 2014 14:24
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cut a of 4 in. piece of big 0 into 16 in lengths . cut the short pieces in half along their length . insert upside down between rafters .about 25 cents each.
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Wilbour
Member
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# Posted: 30 Mar 2014 15:27
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Just...
Can you say that again in Canadian? 
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Just
Member
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# Posted: 31 Mar 2014 23:14
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Quoting: Wilbour say that again
I'll try
If you cut a 4 in plastic tile in half along its length then cut the c shaped tile into 16 in peace's, Place one in each rafter space at the wall perimeters . This allows air from the soffit vents into the attic space to keep it cool and dry. often this space is blocked by insulation .
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