Sub Slab Vapor Retarder: Is two layers of 6 mil poly acceptable alternate to one layer of 10 mil poly?
johnringel
| Posted in Building Code Questions on
The 2021 IRC requires sub slab vapor retarder to be 10 mil poly. I am told by masons this is very expensive product, and does not come in convenient sizes, nor is it readily available. They request to use two layers directly on top of each other with staggered seams as a more manageable and economical option.
Is this an acceptable alternative.
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Replies
Stego is readily available to anyone with the internet in 10mil or 15mil.
Would 5mil double pass? I don't know.
Will 5 mil alone that is rated as a vapor barrier be a vapor barrier? yes.
If asking is two 5 mil = the same strength of 10 mil, no.
That is silly, it is .06/sf for 6 mil vs .08 for 10 mil at Home Depot in the exact same size, 20x100
Also I would say no, that is not a good alternative
5mil does not meet the Class A vapor barrier.
Double stack therefore is not correct.
If it passes, it shouldn't have.