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Placing poly on concrete wall and slab

b4316207 | Posted in General Questions on

So I am building a new home zone 5 philadelphia area , construction started foundation wall are poured ,

basement and foundation are about 60% below grade 40 % above grade
at present placed 2″ xps around whole foundation question is about insulation and placing poly on inside

I was reading article on GBA air seal mudsill assembly

in it they use EPDM gasket as part of mud sill assembly plus poly plus Acoustical sealant
1)is that still recommended way to go ?

2) if yes then poly is run from top of mudsill to inside wall and gets taped to slab , will this air seal technique cause mold build up on foundation wall if it all gets sealed in.
as side note I was reading on web site where they even tape poly to cover xps on exterior of foundation wall

3) if the above is ok to do was planing on placing 2″ xps on inside wall of foundation should wall be
A) concrete , poly, xps, or
B) concrete , XPS , poly,
I plan on finishing the basement

as always thank you for the great help

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Boris,
    I'm not sure which GBA article has the polyethylene detail you are talking about.

    In general, I don't advise installing any polyethylene near the rim joist, mudsill, or as part of an insulated foundation wall.

    For information on insulating basement walls, see this article: How to Insulate a Basement Wall.

    For information on insulating rim joists, see this article: Insulating Rim Joists.

  2. user-2310254 | | #3

    Boris. That article addresses building to Passive House standard, and the drawing you cited concerns how to detail an insulated above grade slab and crawlspace. The links Martin provided are appropriate for the type of foundation you are doing.

  3. b4316207 | | #4

    OK thank you, So the question stands should poly be used on the above grade portion even if you are not building to passive house standard

  4. GBA Editor
    Martin Holladay | | #5

    Boris,
    Steve is correct. The article is talking about a slab on grade. A slab on grade always requires polyethylene under the concrete slab. Extending the polyethylene under the mudsill (for this type of foundation) is possible but optional.

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