Mold Within 2" Rigid Thermax--Polyiso
Three years ago we remodeled a basement in a 1920's vintage house. The foundation is poured concrete. In all but two little 8'x8' areas we sprayed 2-1/2" of a closed cell urethane foam over Platon drainage matt which was installed directly to the concrete wall. The Platon was channelled into a subslab drain tile that we cut into the floor. We then installed 2x4 walls, uninsulated and drywalled. Since the two little rooms were not finished with drywall and too difficult to install drain tile we decided to simply install 2" of Poly-iso (Thermax) with taped seams, glued directly over the concrete wall. Now three years later, we are adding a small kitchen addition with a full basement that connects to one of the 8'x 8' areas. When we pulled off the poly-iso to cut in the opening to the new basement, the foil face stayed on the wall and we found black mold between the foil that is in contact with the concrete and the foam itself, down the entire length of the poly-iso . The owner has never seen any bulk water at the floor so my only conclusion could be that this is an extreme condensation event perhaps as a result of vapor drives through nail punctures on the interior foil face and/or from the top and bottom of the Thermax where it meets floor and mud sill. Would adding Platon over the concrete then installing new Thermax over that prevent this from happening again even though the Platon would not be channeled into a subslab drain tile? We would also be much more diligent in sealing all nail holes, seams, etc. By the way, we did not open up the areas that were spray-foamed over Platon--(That worries me too!)
Posted Jul 14, 2011 10:26 AM ET
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