I am new and interested in the value of the rigid t&G foam over the subfloor. I am doing a 14x24ft addition to the rear of my house. 12'x12' was an old patio, I removed the patio slate, that leaves a sand filled base. I didn't want to hammer out the stone wall and remove all the sand. Also it holds up the balance of the patio which is being left in place. I don't know how to insulate this area. The rest of the building has a crawl space of 2 1/2 to 3 1/2 ft. Maybe the best thing would be for me to do the t&g rigid form board over the whole thing. I have pressue treated 2x12 floor joists. Will that work? or is there some other insulation that I could use in that old patio area. I'm placing black vapor barrier on the whole ground, including the old patio.
Are you looking at putting T&G Insulation on top of the floor joists? If so you may need to put a subfloor down first, then the insulation then another layer of osb or plywood. Even though T&G insulation can be rated for upwards of 250psi, I'm not sure I'd feel comfortable having it laying directly on joists. Also you could put the foam insulation between the joists.
What part of the country are you located ?.
I was putting 3/4 inch t&G advantec subfloor down on the joists. I was going to use the foam insulation on top of that, between it and maybe a hardwood finished floor. I am in WV.
Thanks.
I'm assuming you can't work from the bottom of the joists and that the joists are open at this stage. I would not put a hardwood floor down on top of foam board. You would have to face nail it with big hunkers and even then it would want to move and pop the nails.
How about if you put wire retainers between the joists, drop in fiberglass batts and then put down the subfloor. If these are 2x12s you could get R-38 in there for the cost of R-10 formboard and with a lot less hassle.
But then again, I may not have the right picture in my head. d*
I think your right, maybe the old post I read had the person putting down the formboard on the subfloor, then putting another 1/2 subfloor on top of that. That's too much subflooring.
I'll try to get photos out here this weekend, if I don't get frustrated and throw the camera and computer over the hill.
As a mechanical engineer friend (?) told me, that he would have demolished the patio -stone wall and removed the fill and sand- back to ground level to have a sufficient crawl space under there. I wanted to leave it in place because I'm only using half the patio, and the balance of the patio is still in place. I did dig out a one foot wide space and filled it with concrete to help support the remaining patio, in case I have to remove the old fill. I already have the joists nailed in. I removed the patio slates and graded the sand to slope off, in case any water got in there. I figured it would run down the 6mil vapor barrier like a water slide.
The space between the treated 2x10 floor joists and the sand is anywhere from 2" to 6". I can still put in wire retainers and the insulation, but it will be close to the vapor barrier. If do this and get some type of moisture problem, I can hammer out the stone wall and remove the sand fill. Nothing like digging on hands and knees like a coal miner.
Like I said, I'll try to get photos.