I am an Architect and am working on a historic building. The building was built with no building paper substrate. The plaster was applied over 3 inch thick ceramic tiles over studs. If we provide elastomeric paint, will this provide a waterproof membrane with a warranty?
Elastomeric paint will form a film that prevents moisture penetration. Plus, it will allow any accumulated moisture out of the walls, a major plus for any old building. With a good brand it will last for many years and be easy to maintain.
A good brand that should be readily available in your area is Kelly-Moore. Their 1128 Elastomeric Coating is a great product, one that I have used many times. I believe Kelly-Moore offers a factory warranty.