Waterproofing Roof Cap Stone, EIFS Siding and Terracotta Block

LESLIE: Heading on over to Clint in Texas with a question about waterproofing. How can we help you today?

CLINT: Would like some recommendations on a good waterproofing for the cap stones on my roof. My house is a commercial-style building with a flat roof and the parapet is crowned with cap stone. And I need to waterproof that. And I have an exterior that is EIFS and it needs a good waterproofing. And then part of the home’s exterior is also terracotta block. I think the concrete is letting water soak down into it and then when it freezes, it shatters.

TOM: Alright. Well, starting with waterproofing, OK, at the parapet wall, what you want to use is simply a silicone-based sealer for that, since it’s a masonry product. So a silicone waterproofing sealer for masonry is what you would use there.

Now, the more difficult matter is when you mentioned that you have EIFS. And EIFS is exterior insulated foam siding. This is that siding that looks like stucco but it’s not; it’s foam.Now, do you happen to live in a home that’s masonry or is it a wood structure?

CLINT: No, it is built all out of these huge concrete blocks that you would normally see in commercial …

TOM: Alright. Good. Because if you were living in a wood structure that had that same type of siding, I would say you had a serious waterproofing problem on your hand, because the EIFS leaks like a sieve.

I am not sure what the appropriate coating would be for EIFS over a masonry surface but I know that there’s not as much concern about leakage. Because even if it does get in, it typically gets into the joints. It’s going to strike the masonry underneath and not cause rot. The problem with that stuff is when you put it on a wood house, the moisture gets into the sheathing and studs and it causes decay, which is serious trouble. So I can’t help you about that.

Now, what was the third part of your question, about the cracks?

CLINT: I have some terracotta – some decorative terracotta – in the walls, around mostly the pool. And that terracotta has a concrete cap stone, also. But water is seen to getting – it’s getting into some of the terracotta. And then when it freezes in the wintertime, it breaks the terracotta apart.

TOM: I wonder if there’s ever been a sealer put on that. Because if you put the wrong sealer on it, that very condition happens. If you put a sealer on that’s not vapor-permeable, which is a type of sealer, the water gets in but it doesn’t evaporate out. You’re never going to completely 100-percent waterproof your terracotta block but if you put the type of sealer on that’s vapor-permeable, then that allows moisture to evaporate out. So I think that’s what you’re going to need to do.

CLINT: Alright.