Sealing inside of house sill plate
Hill_Builder
| Posted in General Questions on
Tried to find the answer on what to use to seal between the concrete (slab on grade with in floor heat) and sill plate inside the house. I am assuming to just use caulk. If so, is there a preferred type of caulk?
Silicone, latex or others?
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Replies
Acoustic caulk. And not an acrylic base one. The traditional acoustical caulk is latex based and stays flexible (forever?)
thanks
Hill_Builder,
Another option is a gasket on the underside of the plate.
Whether it's even necessary depends on where your primary air-barrier is. If it's the sheathing then you should either seal between it and the concrete below on the exterior, or if you do seal on the inside of the plate make sure the sheathing is sealed to that plate at the exterior or you will have a bypass.
We already have the sill gasket and we sealed the outside where the sheathing meets the concrete blocks with Prosoco. We want to seal the inside too. Belts and suspenders approach to make sure we don't miss anything as we are on a super windy hill with lots of bugs too.
I distinctly remember a past Q&A discussion similar to the one I link below (although there may be more) that discussed how manufacturers actually recommended urethane caulks over acoustical for this purpose:
https://www.greenbuildingadvisor.com/question/polyurethane-vs-acoustical-caulk-for-air-sealing
We had already purchased Tremco 116 to use, but now see it says definitely not for indoor use.
If it's sandwiched between the sill and the top of a foundation wall, I'm not so sure I'd consider that to be "indoor" use. Indoor would be something like a countertop or bathtub where the bead of caulk is entirely exposed to the living space.
It's been my experience that urethane cualk is far, far more durable than latex, and even silicone. I like to use it for anything that I need to last, which includes sealing up air barriers that are concealed within other assemblies.
Urethane sealants are pretty stinky when first applied and during the curing process, but after a few days the stink is pretty much gone.
Bill