Air Sealing top and bottom plates?

Old 07-10-18, 01:38 PM
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Air Sealing top and bottom plates?

In my basement finishing project, I have an exterior wall which I'll be framing over and insulating with fiberglass batts in the stud cavities. I'm reading through MN code, and I've come across the following line:

R402.1.1.7 "2. The top and bottom plates shall be air sealed to the foundation wall surface and the basement floor."

Can anyone explain to me what that means and how I'd go about implementing it? I haven't been able to find much clarifying information.
Old 07-10-18, 02:25 PM
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Bottom plates generally get set on top of a "sill sealer" gasket as the wall is being constructed. It's probably underneath the plate already. If it isnt, you will want to caulk the plate to the floor with something like Loctite S10.

If you have a side wall, as most walkout basements would have, the same thing would apply to the sides of the framing where they meet the concrete foundation walls.

Not in the code, but it's often a good idea to caulk the exterior sheathing (do this from inside) to the top of the bottom plate. That's also a prime spot for air infiltration and that cold air usually causes mold behind the baseboard when it hits warm air.

Double studs can be caulked down the middle (king and trimmer... header ends) and the seam between the double top plate. If you have electrical outlets it's often good to stick a little square of rigid foam in the space between the box and the sheathing... better than fiberglass.

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