How to Clean Masonry
If you have a brick home, you probably have some problem spots in your masonry, such as mold growth or oil and paint stains. If these unsightly areas bother you, you can clean them. The most common masonry-cleaning problems and solutions are listed here:
Fungus, moss, and mildew: One quart of household liquid bleach mixed into 1 gallon of warm water, applied with a stiff-bristle brush, usually takes care of these unsightly problems. (Don’t forget to rinse the solution off with clean water.) However, sodium hypochlorite, the active ingredient in bleach, may not dissolve large masses of these types of growths. In such cases, scrape off as much of the crud as you can with a broad-bladed putty knife (or wire brush); then scrub on the killer mixture.
When trying to eliminate fungus, it’s the bleach that does the job — not the elbow grease. Make sure you give the bleach plenty of time to work before scrubbing and rinsing away. If not, fungus spores will remain and can grow back quickly.
Oils, soot, and mineral residue: Oils, soot, and white, powdery mineral residue pose a slightly more difficult problem. They’re embedded more deeply than moss or mildew into the pores of the masonry. You need a solution of 1 part muriatic acid to 9 parts water to get rid of this hard-to-remove crud. Add the acid to the water and apply the solution; allow it to set for about 15 minutes; then use a bristle brush to clean the affected area and rinse with fresh water.
Paint: Sandblasting, wash-away, or peel-off paint removers; hand or electric wire brushing; muriatic acid washing; and power-washing are just a few of the ways that you can remove paint from masonry. Sandblasting or wire brushing is hard, messy work, and paint removers sometimes create more mess than they eliminate. Instead, you can rent a commercial power washer for about $50 per day. It’s easy to operate, mess is kept to a minimum, and you don’t have to be a chemist to make it work. Be aware, however, that a power washer works fine on the outside of your home, but all that water could wreak havoc on the inside of your house. Therefore, when it comes to removing paint from brick or stone, your best bet is a chemical stripper such as Peel Away.
Applying a sealer can minimize brick or stone damage from salt air and severe weathering. It can even work to prevent efflorescence. Just as you would with concrete, you need to thoroughly clean your brick and stone before applying a sealer.