- Q. What is the best way to protect exterior foundation foam insulation where it projects above grade?
A. While there are a number of trowel-on or paint-on coatings on the market, I have found that most of these coatings chip easily. My choice is a strip of 1/2-inch foundation-grade (FDN) pressure-treated plywood (see illustration). It can take a lot of abuse and can be painted or stained any color.