You can apply over most acrylic/latex, polyurethane, alkyd paint, epoxy paints/coatings with proper cleaning/preparation techniques. Keep in mind that when you apply over an existing coating or paint, if that coating/paint peels, our coating will peel with it as it is bonded to the existing coating/paint and not directly to the substrate.
It is recommended to remove oil based or recently applied coatings with high solvent content prior to applying your Ziollo products. (oil interferes with bond/adhesion and solvents can deteriorate our sealant). If there is an existing Silicone Roof Coating on your RV you should be able to bond to it with Ziollo RV Roof Sealant but not with our Lap Sealant or Seam Tape