A reader wants to resurface a concrete wall that has crumbling faux-brick plaster. (Reader photo)

Q: We would like to resurface the concrete walls next to the steps leading to a walk-out 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?

Woodbridge, Va.

A: When a topping such as your faux-brick material bulges or becomes coated with crusty mineral deposits, it can be 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 (xypex.com), a company in British Columbia, Canada, 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 discoloration. The only dark streaks are where the handrail connects to the wall, and that’s probably rust caused by rainwater interacting with the metal.

Dave Ross of Xypex Chemical Corporation suggests cleaning the wall, patching the places where the coating has broken off, repainting, and then installing flashing that wraps over the top of the concrete and the top edge of the faux brick to help keep the edge from crumbling again. (Reader photo)

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 ($7.78 at Lowe’s ). It’s three pounds of dry mortar mix packaged so that you can just open the thick plastic bag, add water (1¼ cup) and knead through the plastic to mix 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 ⅜ - or ½-inch-wide for $6.15.

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 labeled for use on exterior brick, such as Behr Multi-Surface Interior/Exterior Primer and Sealer ($22.98 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 ($21.98 a gallon at Home Depot).

It’s possible, of course, that there is more damage to your wall than the pictures show. If the topping is bulging out or if there is heavy efflorescence, you will need to chip off as much of the existing topping as you can. Once that’s off, inspect the concrete to see where moisture is getting through. If you find a few cracks or rust stains around remnants of tie wires (these are what held the forms in place when the concrete was installed), chip out a recess about an inch deep and at least an inch or so wide and patch it with one of the mortar products. If possible, undercut the edges of the recesses to help keep the patches in place.

If you find that moisture is seeping through the wall in a general way, rather than through a few specific spots, you’ll need to seal the concrete. There are lots of masonry waterproofers on the market, but my brother, who is a masonry contractor, said the best product he’s found is Xypex Concentrate. It causes crystals to form in the pores of the concrete, turning a porous surface into one that moisture cannot penetrate. It’s sold through distributors that cater to contractors. One online source is DHC Supplies (dhcsupplies.com), where a ­
20-pound pail
costs $75.

Once the wall is sealed, you can then install whatever topping you want. Stone veneer or brick veneer, which are manufactured products about ½-inch thick, can look classier than a faux treatment. Hire a mason if you don’t want to tackle this job on your own.