Poly under the sill plate
AJ__
| Posted in General Questions on
I’ve seen a few projects use poly under the sill plate with traditional sill seal on top. Steve Baczek’s passive house build featured on this website comes to mind.
When does this become a good idea? I’m soon to begin framing and undecided on whether to include this or not. What do I lose by not including it?
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Replies
Alex,
I'm struggling to think of what purpose the poly would have that the sill-seal doesn't fulfill. What's your air-sealing strategy at the bottom of your walls? Tape? Sealant?
Liquid flash from sill to framing and maybe another bead of sealant between the concrete and sill seal, or on the interior where framing meets the concrete.
Maybe someone else has an insight into why Steve Bazek used it?
Sill sealers are almost never airtight. The poly is the air control layer and is connected to the wall's air control layer. At least that's how I often detail it. There are other ways to ensure a continuous air control layer.
Thanks Mike,
So Alex is fine omitting it as his air control layer is the sheathing and he is sealing it to the stem-wall.
Is the air air control layer on the outside or inside in this case? Would taping the wall and foundation on the outside or acoustical caulk on the inside accomplish the same thing?