Insulating rim joist over thick rock foundation
I am working on a 1923 three story farmhouse with a rock foundation in climate zone 4. The foundation walls vary between 18″ and 20″ thick, conveniently covering the joist bays. In spots, I have approx. 1 1/2″ clearance between the top of the foundation walls and the joist. Some of these spots are jammed with fiberglass batts, others are sealed with spray foam. Flooring is 3/4″ pine over 8″-10″ subfloor run diagonally (lots of spots for leakage). Walls are uninsulated plaster and lathe. My issue is that the homeowner wants to insulate and air seal the joist bays to stop drafts coming through to the first floor. I have no access to this joist bay from any angle. There is not enough room to get a spray gun in reliably through the entire joist bay. Need a creative solution to tackle this one. Pictures are attached.
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Replies
You can use that stuffed in batt as a backer for spray foam if your primary concern is air sealing.
If you can’t get in there with a “real” spray foam gun, you could try canned foam with the straw. If you still can’t get in there, get some flexible vinyl tubing to make an extension for the straw. This tube can be several feet long if needed, and can be poked into hard to reach spots. Sometimes using some stiff wire like a wire coat hanger or a wood dowel will work as a tool to guide the tubing. You can use the wire to make the tubing formable so that it will hold bends you make if you tape the wire and tube together.
The downside is that the longer you make the extension tube, the more foam will ooze out the end after you stop pushing the valve down on the can. Basically longer tube gives better reach, but also more mess. Sometimes it’s the only option to get into screwy places though.
Bill