Shimming and air sealing sill plate
I’m getting ready to frame the garage for my project and the foundation walls aren’t dead flat and level (are they ever?) so I need to shim the sill plate. But the sill plate is part of a conditioned crawl space system so needs to be air sealed.
Best practices for sill plates, from everything I’ve read here include
– make sure there’s a capillary break between the top of the foundation and the sill plate;
– make sure there isn’t an air gap between the concrete and the sill plate
– make sure the sheathing is sealed to the plate, and that the plate is air sealed to the concrete.
In the real world, how do I do this? Questions include:
– What’s the best material to use for the capillary break? I have some 10 mil poly, or I could round up some EPDM from an unused pond liner and cut strips… or use a butyl flashing tape like Vycor. What do you use, or recommend?
– The traditional method of “shim, then grout” won’t work if the capillary break is sitting on the concrete, so it needs to be attached to the bottom of the plate. What to use for shims?
– has anyone found a good method for reliably inserting grout into the thin (shimmed) spaces under the sill plate? Should I just run a thick bead of something that will harden (like fireblock caulk) on the top of the foundation wall as the grout, before bolting down the plate?
– and, finally – having done all this, is there still value in using something like the Conservation Technology plate gasket, or should I just use a great flashing tape to seal the plate to the concrete?
Thanks for the advice – this green building stuff gets complicated quickly!