How to seal 4″ EPS foam at slab edge (radon concerns)?
Basement concrete 4″ slab to be poured on top of 10mil poly, 4″ EPS (2 layers staggered seams), and gravel at bottom with perimeter drains connected to vertical radon vent pipe. Building in a high radon zone, will the poly be sufficient covering the 4″x4″ foam perimeter strips not covered by concrete at the slab edge? Should I be tapering the foam edge instead of keeping the full width of 4″x4″ strips?
Tips for poly location at edge detail during pour (ie. multiple creases going over the 4″x4″ foam perimeter strips or just keep the poly flat until it meets the foundation wall and put the 4″x4″ foam perimeter strips on top of the poly?) How do you recommend sealing the poly to the foundation wall?
Will eventually be covered with a thick (5 1/2″ – 7 1/4″ depending outside grade) EPS foam and drywall, so aesthetically not a concern. But worried that radon may leak through – what to use to seal 4″?
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