Q: The interior walls of our 1934-35 garage are deteriorating. They appear to be made with multiple rows of terra-cotta blocks separated by single rows of bricks. A former owner of the property drilled into the blocks, leaving holes, and is probably the one who painted the interior white. Outside, the walls are faced with painted brick that have some moisture showing because of our neighbor's tall trees.

The garage is infested each year with camelback crickets, which we exterminate annually. We'd like to keep our new car in the garage when we're out of town or in advance of bad weather. We don't want the car infested with crickets. Is there a way to repair or bug-proof the garage, fill the holes and paint/stabilize it with some sort of moisture-proof paint?

Washington

A: About the crickets: Although they might look scary, they are generally harmless. In fact, some people rear them in aquariums as pets or as fish bait. And there are even recipes for converting them into snack food. (Do a Web search for “dry-roasted crickets.”)

That said, these crickets are also known as cave crickets. They’re called camelbacks because of their humpback shape; their second common name refers to the kind of environment they frequent. Get rid of the cavelike moisture in your garage, and they will probably go elsewhere.

However, the only sure way to eliminate the moisture is to waterproof the exterior of your garage, which may be more work than you want to tackle. It would require digging down along the building, adding waterproofing to the outside and directing water away in a buried pipe or by sloping the soil. It would probably mean re-landscaping the area, too.

Short of that, there are simple steps you can take to improve the situation, at least for a while. Begin by scrubbing the walls and scraping off loose parts of the previous white coating. Avoid using a power washer, because too high a pressure can damage the bricks and mortar. Instead, scrub by hand with a scrub brush. Use a stiff putty knife to knock off loose chunks of the coating, which appears to be thicker than regular paint. It could be an old cement-based product.

You should wash the walls with a product that removes mildew. On the unpainted areas, you also need to use a product such as Drylok Concrete and Masonry Etch and Cleaner ($7.84 for a 12-ounce container at Home Depot). But you might want to do as much of the cleaning and scraping as you can using plain water first, and then follow up with the other cleaners. With water, you don’t have to worry about fumes or splashes. With mildew remover and concrete etcher, you’ll need eye and skin protection.

Let the walls dry, then test whether the surfaces are sufficiently sound to hold paint: Press masking or packing tape at various places on the walls, including both painted and bare areas. Quickly yank off the tape, and check whether it has taken off old coating or bits of the blocks or mortar. If this happens, you’ll need to scrape down to a sound surface, probably with a wire brush. Test the paint first to ensure it doesn’t contain lead, and be sure to protect yourself against breathing dust. An N95 disposable respirator with a vent valve works great in this situation, and using it won’t cut into the supply of vent-free masks needed for protection against the novel coronavirus.

Once the walls are clean and sound, patch the holes the previous owner cut. Terra-cotta blocks are made with a honeycomb structure that leaves air gaps running horizontally, rather than the vertical cavities found in concrete blocks. But mortar works fine for patching holes in both types of blocks. Mortar mix is often sold in bags that weigh 50 pounds or more, but a 20-pound pail of Quikrete Fast Set Repair Mortar Mix ($19.18 a pail at Home Depot) should be more than sufficient. This product is formulated for patching even overhead cracks or holes, so it should be stiff enough to grip the relatively large holes in your wall. But if you find that the mortar keeps pushing through, squirt spray foam insulation, such as Great Stuff Gaps and Cracks ($3.78 for a 16-ounce can at Home Depot), around the back of the holes to give the mortar something to rest against. Or use pieces of broken bricks to plug part of the holes and mortar around them.

For holes where water seeps through, you need a different plugging product: hydraulic cement, which expands in place as it becomes moist. (Drylok Fast Plug costs $9.70 for two 1.5-pound containers at Home Depot.) One of the pictures you sent hints that water seeps in along the bottom of the wall where you store your ladder, a place you definitely need to plug.

At last, you’re ready to paint, but you might want to wait 30 days after you’ve patched, so the mortar fully cures. (Or just avoid painting the patched areas and coat those later.) Use a product such as Behr DryPlus Masonry Waterproofer. The instructions say it’s best over bare concrete or masonry and that it can also be used on previously painted masonry walls, provided the old finish is sound. But the company does not guarantee the results over old finish, which is a good hint that you might find yourself needing to redo the finish frequently, especially on the bottom rows of blocks.

If there is electrical service in your garage, you might want to keep a small shop vacuum in a corner to remove water that gets in after heavy storms. Even if you don’t do it daily, keeping your garage as dry as possible will make it less cavelike — and thus less hospitable to the crickets.

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