Going to the wall
Time to consider resurfacing concrete barrier with peeling, crumbling plaster
Q We would like to resurface the concrete walls leading down the steps to a walk-up basement. When the house was built 15 years ago, the builder covered the walls with some type of faux-brick plaster, which is now crumbling and peeling. What can we do to bring the walls back to a nice appearance?
A When a topping such as your faux-brick material bulges out or becomes coated with crusty mineral deposits, it’s a sign that water is getting into the concrete from soil pressed against the other side of the wall. If that were happening, it might be worth chipping off the coating, addressing the moisture issues and applying a new decorative treatment.
But judging from the pictures you sent, your wall is in pretty good condition, said Dave Ross, head of technical services for Xypex Chemical Corporation, a company in British Columbia, that makes concrete waterproofing products.
Describing himself as “an extremely lazy do-it-yourselfer,” he said you probably do not need to redo the faux brick or use waterproofing products. He couldn’t detect any evidence of the mineral deposits, known as efflorescence, or streaks of discolouration. The only dark streaks are where the handrail connects to the wall, and that’s probably rust caused by rainwater interacting with the metal.
Ross suggested that you just clean the wall thoroughly, patch the places where the coating has broken off, repaint, and then install flashing that wraps over the top of the concrete and the top edge of the faux brick to help keep that edge from crumbling again.
Make the patch from mortar, which is probably what is in the existing coating. Mortar mix is usually sold in bags that weigh 40 pounds or more, but some stores carry 10-pound bags. To patch a very small area, you might want to buy a product such as Quikrete Zip and Mix FastSet Repair Mortar ($9.49.at Lowe’s.) It’s three pounds of dry mortar mix packaged so that you can just open the thick plastic bag, add water (11/4 cup/310 mL), and knead through the plastic to mix the mortar into a smooth dough. It even includes a plastic trowel.
Whichever product you use, trowel the surface flat, then press in faux-mortar joints that line up with the existing ones on the wall. Home Depot sells a brick jointer that shapes joints 3/8- or 1/2-inch-wide for $8.75.
For the flashing, stay away from aluminum, which may corrode in contact with concrete or mortar. Galvanized steel or even plastic flashing is fine. Stainless steel and copper are also good options if price isn’t an issue. If you can’t find suitable material, a sheet-metal company can custom-bend what you need. The flashing should cap the top and extend down the sides enough to cover the top of the brick layer. This will guide rain runoff down the outside of the faux brick and keep it out of the joint between the brick and the concrete. The freezing and thawing of moisture seeping in there is probably what caused the damage.
To repaint, wait at least one month for the mortar patch to cure. Then prime at least the bare mortar, or you can coat the whole wall. Use a water-based primer and sealer labelled for use on exterior brick, such as Behr Multi-Surface Interior/Exterior Primer and Sealer ($20.97 a gallon at Home Depot). For the top coat, use an exterior water-based paint for masonry, such as Behr Masonry, Stucco and Brick Paint ($43.97 a gallon at Home Depot).