Ask the Architect

Repairing siding


Q. We bought our house six months ago and had to repair several things. One of them is the concrete below our siding, which is falling apart in many places. It’s crumbling so much that we’re concerned that the house could fall in those places. There is some concrete left, behind the crumbling areas. About two inches of the concrete has fallen away. We haven’t noticed water in our basement, though. Two contractors gave us an estimate. One was for stucco for $600, and the other was for $2,500 to use a concrete sealer. What should we do?

A. You need to know more about what anyone who’s giving you a price is going to do. I would want to know the surface area that needs work. Is it all around the house and 90 linear feet 2 feet tall, or one side of the house and 5 feet wide and 10 inches tall? There are several different methods of repair, and depending on the method, it can be determined how long it might last and why it costs more.

Since you said that water isn’t coming into the basement, it would seem that the damage to the exterior walls hasn’t gone all the way through. The first thing to test is the integrity of the wall in the areas where the crumbling surface has fallen away. The crumbled areas should be cleaned away with a heavy-duty wire brush, and the remaining concrete can be prodded with a steel rod, gently enough to determine if the remaining wall is sound without breaking through. Two inches deep that has crumbled away means that there may be approximately 6 to 8 inches left in a standard foundation wall.

In either case, whether using a stucco finish or a sealer with a paint-like finish, the patch that’s applied must be a commercial-strength epoxy or urethane-based compound, either ready-mixed from a container or mixed on site to manufacturer’s instructions. The best time to do this type of work is in 60-degree temperatures with slightly overcast skies, because higher temperatures and direct sunlight can change the setup time, and the curing of the materials can expand too quickly in hot weather. In that case, the repair may be weakened. The stucco finish versus painted sealer finish is also best applied in 60-degree temperatures, and the more important issue is that the surface finish must be able to breathe so that the finish allows water (moisture) to evaporate.

The reason for the spalling or crumbling condition was due either to trapped moisture that froze and expanded, causing the surface to pop off, or to disintegration of a weak cement mix during the original forming of the concrete, whether it’s a concrete block or full poured wall. Concrete is porous and soaks water in like a sponge. Find out more about the chemical compounds before deciding.

© 2017 Monte Leeper. Readers are encouraged to send questions to, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.