Sill seal
StephenInCalgary
| Posted in Green Building Techniques on
Can XPS rigid foam be used atop the basement wall in company with, or instead of, a sill gasket?
What is the best way, or material, for a sill gasket?
Thanks
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Replies
The foundation sill has the weight of the house bearing down on it, and is likely to exceed, the elastic compression limits of the foam.
Purpose made EPDM sill gaskets are hard to beat for air sealing, and as a capillary break between the concrete & wood.
ok thanks.
Conservative Technologies makes a good epdm gasket.
Hi Stephen -
Sill gaskets, in addition to being an air seal, should be a capillary break. To be a cap break, the material must be non-porous. EPS porosity is to high to be considered a cap break. XPS insulation on the other hand is non-porous and can function as air seal and cap break, as can the EPDM gaskets.
Peter
>"XPS insulation on the other hand is non-porous and can function as air seal and cap break, as can the EPDM gaskets."
Capillary draw issues aside, XPS should not be used under a load bearing wall without doing the math. It can't be recommended as a generic solution under sill plates supporting walls & joists the way EPDM sill gaskets can.
In addition, a gasket is applied quickly and gets stapled to the bottom of the mudsill. Cutting up xps and sticking it to the sill ( sealant?) takes more labor time.