Exterior brick is best cleaned by starting with water, a brush, and the mildest compatible cleaner because excessive pressure and acids can erode mortar or alter color. Before cleaning a whole wall, identify whether the problem is dirt, algae, efflorescence, or a specific stain and test a small area.
Start by brushing and wetting the surface
Remove dust, webs, and loose material and pre-wet the brick from the bottom upward before applying cleaner. Partial saturation reduces rapid product absorption and helps control streaking.
Use a nonmetallic brush and compatible cleaner
Work in small areas with a firm nonmetallic brush. Avoid generic acidic cleaners on mortar, older brick, or unknown masonry until compatibility is confirmed.
Pressure washing can damage mortar when used too aggressively
If pressure washing is appropriate for the brick condition, use a wide fan, distance, and moderate pressure. A concentrated jet can erode mortar, damage soft brick faces, and drive water behind the wall.
Efflorescence needs a moisture diagnosis
White salt deposits return when water keeps entering and evaporating through masonry. Brushing can improve appearance, but leaks, caps, or drainage problems need correction to prevent recurrence.
Sources
- American Cleaning Institute — Cleaning Tips — Household cleaning methods, product use and dosing, and material compatibility.