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QUESTION: I’m building a shed roof addition off of my house. I want to build the (one) bearing wall directly on the 2 X 8 floor joists and then put the addition under roof before I put down the subfloor. Is there any reason I shouldn’t do this? I plan to rip a piece of 3/4″ plywood to put under the bottom plate of the stud wall.
The addition will be on a crawl space and won’t have access from below.
The reason I want to do it in this sequence is because I’m insulating the floor and when I built the main house structure the insulation got wet and I had to pull the floor up and replace the insulation. Since I’m working by myself I won’t be able to get the roof up very quickly and so I want to delay insulating the floor until it’s protected.
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I can't think of any reason not to do this. The only problem I can imagine is that your joists may tend to roll or spread without the sheathing in place but as long as the floor is eventually sheathed up to the sole plate of your load bearing wall, I think it would be fine.
*Michelle,Reminds me of a situation I got talked into early in my career. During an addition project for which the homeowner wanted to insulate ( the guy was loaded, probably cost him more than if my sub did it!) and talked me into letting him do it before I put the subfloor down. I spent a bunch of time and money to keep it dry but it inevitably got wet. What a mess! Not only is providing access to your crawlspace smart, but is required by BOCA 1211.1, and probably other codes. 18x24 inches to be exact. I can see no reason to insulate the floor prior to subfloor. It is costing you time and its just plain goofy. Believe me, I'm all for innovation but I think your past experience and mine begs that you don't reinvent the wheel.Pour a mudslab on sand and vapor barrier, float it reasonably smooth, and modify a creeper to install the fg if you insist on doing it yourself. Better yet, hire an insulation sub, he'll supply and install for just a few cents over what you'd pay to buy the stuff at the home center.Tom
*I always insulate before putting down the floor. I hate working in a crawlspace. I can insulate a floor in an hour that would take me half a day from below. I staple the insulation in place with the kraft paper above (supported on either sticks nailed to the underside of the joists or now, Ijust lay down plastic sheeting first and let it sag between each joist), I then do another layer of plastic over the insulation, pulled tight and stapled.I then sheath and keep building. I do take a knife and cut alot of slots in the lower piece of plastic every few inches. If water ever gets into the insulation, I don't want it trapped between two layers of plastic.
*Sounds like you'll be creating a bit of a headache when it comes time to sheath the floor. How will you support the edge of ply that butts to the strip? Use blocking, or will the strip be the groove end of T&G? Also, placing remainder of the ply will be a pain when you get up to the other wall. Further, it seems like it would weaken the floor diaphragm-3 1/2" strips have no shear value. Could you compromise and put in a full 4' sheetunder the wall? That's not too bad of a crawl situation and it would be nice to have something to put your ladder on when you do the roof too.
*Thanks for all the comments. I am planning to add an access panel to the crawl space, I just don't want to go down there and insulate if there's another way. And I do plan to tack down some 4X8's for walking on, setting ladders, etc. until I get the addition roofed.There are no codes where I am building so no inspections. I am trying to do everything to code or better but there is some leeway if necessary. Hiring a sub out here in the boonies for any small subcontracts just doesn't work; business is too good for them to fool around with small jobs like this.