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Ask the Expert Question-and-Answer Archive

by Ron Joseph

June, 2006

Elastomeric Paints Over Acrylic Latex

Q. We have been in our house 10 years. A painter identified the paint system on our stucco house as being a Tex-Cote type. He says that if it is recoated with an elastomeric the build-up of tension in the new coating will overwhelm the original one and possibly destroy old and new together. Can you corroborate this? If so, would a exterior acrylic latex paint extend the life of the elastomeric by protecting it, or would it just make it look better until the original coating fails underneath the new? If the latter were likely, it would suggest stripping the old coating off the house. If it comes to this, do you recommend a particular stripping process?

A. I guess that the painter is referring to the potential incompatibility between paints that have different degrees of elasticity, cohesion and/or adhesion. It is possible that if the cohesion between individual or multiple coats of paint exceed their adhesive bond strength to the substrate (in this case the stucco wall) you might experience extensive peeling. Since I am not able to examine the coating system my answer is strictly generic. You might need to experiment with the coating system.

You would not want to apply a non-elastomeric coating over an elastomeric one, because if the undercoat expands and contracts with the movement of the substrate, the non-elastomeric topcoat will crack.

Again, since I have no idea of the condition of your house I can't advise whether or not you should remove the old paint, but that option is certainly a possibility. For similar reasons I can't suggest a method for removing the old paint.

I hope I have give you something to think about.

Best wishes,

Ron Joseph

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