Published on October 13th, 2014 | by Henri


Repainting a house that lacks vapor retarder

Q.   In an earlier post, you commented on a house with wood siding that paint would not adhere to, peeling off within two years, probably because it lacked a proper vapor barrier on the warm side of the walls. This is an issue we are aware of in our home. We are about to repaint our home and I wondered if you could offer any suggestions as to how we may best deal with this.

In my search for useful suggestions on this subject (my thought process hoping for some sort of advanced product to use in our painting) I ran across a product “permanent coatings,” but they were in Vancouver. I didn’t know if that could be an answer or if it is even sold in the states. Nevertheless it made me even more curious as to whether or not there may indeed be a technologically advanced product out there that could bring us salvation!

A.  I do not know anything about the product you mention, but I am very wary of the hoopla about some products that claim miracle solutions. Moreover, this coating is for exterior application in lieu of regular paint. It does not solve the convection and diffusion of moisture into the exterior wall cavities, which are the cause of the problem.

A vapor barrier is needed on the warm side of the exterior wall to prevent moisture from migrating into the wall cavities and causing major paint peeling, and potentially worse problems.

The most important thing to do, to provide an effective barrier to moisture convection into the wall cavities, is to check for cracks and minor openings on walls and ceilings; where different materials meet, such as window and door trim and baseboard; around electrical ceiling fixtures, switch and receptacle boxes. These openings, however minor, should be caulked.

Hardware stores sell closed-cell gaskets that are installed under the cover of switches and receptacles. The walls can be painted with B-I-N, followed by your choice of finish paint or two coats of a low-perm paint.

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