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Wakefield74
Member
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# Posted: 27 Mar 2018 16:03
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My cabin is built on spot piers, about 24 inches off grade. 2x12, 12†on center. Besides a little plumbing, nothing else will be installed in the subfloor. Need to figure out the insulation, vapor barrier and ( wire mesh?) to keep the critters out. Built in south central Virginia on clay. Any ideas?
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Borrego
Member
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# Posted: 27 Mar 2018 22:08
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This has been addressed before....
Most common approach is to brad nail a 1 x 2 to the bottom of the 2 x 12's and cut pieces of plywood (3/8" ) to sit down in the bay....then lay in the insulation, R30, and install your 3/4" plywood floor...
Wire mesh will be useless, might as well use nothing....
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Borrego
Member
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# Posted: 27 Mar 2018 22:08
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http://www.small-cabin.com/forum/2_5253_0.html
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Wakefield74
Member
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# Posted: 27 Mar 2018 22:37
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Ok. Read the threads you attached. Sounds like insulation, then sheathing the bottom of 2x12s. I actually have a good bit of PT 1/2†plywood. I have a long couple of days on my back. Drilling holes in sheathing was one idea I read. Another said to caulk the seams. Thanks for the help
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Wakefield74
Member
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# Posted: 27 Mar 2018 22:38
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Floor is already in. Cabin is dried in. Forgot to mention that
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lburners
Member
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# Posted: 28 Mar 2018 09:54
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I thought this was an interesting approach. Would be interested to see if anyone else had any luck with this.
https://www.youtube.com/watch?v=xPTJD9nuWvQ
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creeky
Member
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# Posted: 28 Mar 2018 19:48
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One thing I used was roxul batt insulation. I think you southern folks call it mineral wool. It doesn't get ruined by moisture and critters don't like it.
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Wakefield74
Member
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# Posted: 29 Mar 2018 17:24
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Borrego, this subject is driving me crazy. Just want to make sure I do this right. After I install the 3/4 plywood, should I caulk everything tight? Some people are saying to drill holes to let it breath, others say no air should pass in or out. I’m a DIY guy, but I need to understand that I’ve done it right.
Others are cutting foam insulating board, 4†thick and installing two layers. They then, spray foam insulate around the edge of second layer. The more I read, the more I’m not sure what the hell to do.
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DaveBell
Moderator
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# Posted: 30 Mar 2018 04:33 - Edited by: DaveBell
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Doing it the right way left the barn when you put the flooring on without insulating the floor. Buy some Foil Faced, 16", R19 so you can staple it. Bow it so you can staple it four inches up in your 12" OC gap. Then, put up your PT plywood and Bob's your uncle.
You should end up with a 4" space, 4" of insulation, and another 4" space. Lots of trapped air. Let it breath defeats the purpose of insulation. Later, use some outdoor silicone caulk around the plywood.
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Wakefield74
Member
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# Posted: 30 Mar 2018 12:52
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“Lots of trapped air. Let it breath defeats the purpose of insulation.“
So if I do it this way, and leave the air void above and below insulation, why even do it? I thought from what I have read, I need to fill the cavities completely with insulation and then sheath it. Followed by caulk or silicone? No air space. Another post read, said do the last step I described, but drill vent holes after completion. Understanding insulation and moisture is not my strong suit. All the help is greatly appreciated.
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snobdds
Member
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# Posted: 30 Mar 2018 12:58
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I bought a 600 BF spray foam kit and sprayed it. It filled every gap, and it keeps the floor nice and warm. It took 1 hour to do.
Don't make mountains out of mole hills...
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DaveBell
Moderator
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# Posted: 30 Mar 2018 13:35
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How dense is a rock?
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Borrego
Member
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# Posted: 3 Apr 2018 20:34
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The spray foam sounds like an easy way out.....wish i woulda done it. If that is not an option fro some reason, then as DaveBell says....use the faced insulation so you can staple it in and then nail your ply over from the bottom...
I would use R30 and not worry about drilling holes in it....
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Wakefield74
Member
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# Posted: 3 Apr 2018 21:56
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I think I’ll attach R30 from the bottom and sheet hit with PT plywood. The way he explained it in his post was 4†air space,4†insulation, then 4†airspace. That’s what confused me. R30 should fill it up. Plywood and then caulk. It’s 24-28†off the ground. Vapor barrier then rock underneath before I start.
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DaveBell
Moderator
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# Posted: 3 Apr 2018 22:54
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Spray foam dripping on you may not be worth it.
2015 IECC Table R402.1.2, Zone 4, Floor R-Value is R19, But if you want R30, go for it. Heat rises.
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