what to do with bottom of vapor barrier?
I’ll be putting a sheet of vapor barrier over the studs in a gable wall. The stud bays go below floor level. Joists are next to the studs with ~1/8 in of space between stud and joist. What do I do with the bottom of the vapor barrier at the bottom of the stud bays? Run it below floor level between studs and joist and silicone+staple it to the side of the joists facing the stud bays?
edit: fixed photo orientation
Replies
You can just slip it down and hold in place against the stud with the insulation you put in the cavity
lay it on the floor while you install the insulation.
if you think you need to seal at the bottom, you can cut flaps on the bottom so they lay on the bottom of the wall cavity. Depends on what is below.
Sorry, don't follow. Do you mean slip it down and hold it place against the joist with the insulation in the stud bays? What's at the bottom of the wall cavity is the top plate of the wall below. There's probably a gap between that and the bottom of the stud, I might be able to get a canned foam gun nozzle in there to seal it.
Also, in the picture, the flooring projects into the stud bays a bit but i can trim that back.
is the wall below complete with a continuous vapor barrier on the interior side of the wall?
My suggestion is based on your description that there is a gap between the wall studs and the floor joist.
You can plan for the vapor barrier to be long, and cut a single slit at each stud location to let the ends sit on the top of the top plate below. The slits would be as long as the top plate is wide. The vapor barrier would then be continuous on the inside surface of your stud wall. Batt insulation would hold this in place. You could add a few staples through the vapor barrier into the top plate to keep things in place as you install the insulation. You can fold or roll the rest of the vapor barrier to sit on the floor as you install the insulation. Then unroll/unfold and install the vapor barrier.
Another option is to make the slits shorter, and tape the ends to the top plate of the wall below.