# Advice for Spray Foam Insulation on Liquid Rubber coated walls



## Kenora_Reefer (Sep 8, 2015)

I live in Central Canada near Winnipeg. We get a wet spring and fall and -40C winters.

I have a basement apartment connected to my house that was constructed below grade with Foundation Grade Plywood for the exterior walls.

We have just had a huge flood and its time to gut and redo the suite.

My plan would be to apply a liquid rubber coating to the inside surface of the floor, exterior walls and studs to waterproof. Then on top of the rubber layer, apply Closed Cell Spray foam insulation, then drywall.

Would this cause any problems with letting the walls breathe or sweat?


Is this something that would work?


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## Windows on Wash (Aug 30, 2011)

Biggest problem is that it won't work. Interior waterproofing coatings don't work. Plain and unfortunately simple. You have to fix the leak from outside. 

If there was no leak and your just asking about the coating, skip it.


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## Gary in WA (Mar 11, 2009)

Welcome to the forum!

Not on the walls, as the vapor barrier should be on outside face of plywood, with *closed-cell* SPF or unfaced XPS on inside face; http://www.buildingfoundation.umn.edu/FinalReportWWW/Chapter-7/7-recs-main.htm
Not on the studs, either- as they absorb/release stored moisture as a cavity buffer- they also dry to the inside.

The rubber coating can be used on the concrete slab, before foam board/plywood or wood flooring; http://www.buildingscience.com/documents/insights/bsi082-walking-the-plank/?searchterm=slab%20vapor%20barrier

Well known in the building trade- - *no ocSPF below grade *on walls, too vapor open, pp.6; http://www.ct.gov/dcs/lib/dcs/offic..._management_files/fa11_spray_polyurethane.pdf

Gary


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