How to Clean an Exterior Brick Wall

The method that works

Start by soaking the wall with plain water. Wet brick absorbs less cleaner, so the solution stays on the surface where the dirt is. Apply a cleaner suited to the problem, let it dwell, scrub with a stiff nylon brush if needed, then rinse with low pressure from the top down. Work in sections so nothing dries on the wall.

That is it. Most brick does not need high pressure at all, and many of the problems people see on brick walls after a cleaning come from using too much of it.

Brick is porous and mortar is softer

Brick is fired clay, and it soaks up water, dirt and stains. Mortar is softer still, especially in older homes, where it may be a lime-based mix. A strong, narrow stream can erode mortar joints, open small gaps, and chip the hard face off older brick. Once the face is gone, the softer interior absorbs water and weathers faster.

Before washing, run a finger along the joints. If mortar crumbles, or you see gaps, the wall needs repointing, which is repair work, not cleaning. Washing a wall with failing mortar can push water into the wall and make things worse. Fix first, clean after.

Efflorescence versus dirt

White, powdery or crusty deposits on brick are usually efflorescence: salts carried out of the brick and mortar by moisture, left behind when water evaporates. Dirt and grime are gray or brown and tend to follow drip lines, splash zones and areas under windows.

Efflorescence needs a different approach. Dry brushing removes loose salts, and a cleaner designed for efflorescence handles the rest. Adding lots of water can dissolve the salts and carry them back in, so they reappear later. If it keeps coming back, there is a moisture source to find, like a sprinkler hitting the wall or a gutter overflowing. Our guide on white stains on brick and concrete covers it in depth.

Choosing a cleaner

For general dirt and light mildew, a mild detergent or a diluted soft wash solution works well on most brick. Mildew in shaded areas responds to dwell time rather than scrubbing. For heavy mortar smears or stubborn mineral stains, there are dedicated masonry cleaners, but stronger products are harsh on mortar and can discolor some brick, so test a small hidden area first and rinse thoroughly.

Always protect nearby plants, windows, metal and painted trim. Wet them first and rinse them after, since masonry cleaners can etch glass and spot metal finishes.

Hard water is another LA factor. Rinse water with heavy minerals can leave faint spotting on dark brick as it dries in the sun. Rinsing in shade or cooler hours and not letting water bead and dry on the face keeps that to a minimum.

Mistakes that damage brick

Using a narrow tip close to the wall. Spraying at mortar joints head-on. Letting cleaner dry on a hot, sunny wall. Skipping the pre-wet. Using a wire brush, which can leave rust marks and scratch the face. Painting or sealing brick right after cleaning before it is fully dry.

Another common one: trying to fix efflorescence with a pressure washer. It looks better for a few days, then the white comes back.

Also watch out for sealers. Brick that has been sealed in the past can look blotchy after cleaning if the sealer has worn unevenly. That is not something a wash can correct; it needs the old sealer stripped or a new coat applied evenly once the wall is clean and dry.

What to expect and when to call a pro

A careful wash removes dirt, webs, mildew and most splash staining. Old rust marks, paint drips and deep mineral stains may only lighten. Brick that has been painted is a different job and should be treated like a painted wall, with low pressure only.

Tall brick walls, chimneys and anything requiring a ladder are worth handing off. For a full house with brick sections, house washing runs $0.35 per square foot of exterior wall as of October 2026; for a brick walkway or border, see our brick border and walkway guide. Say Wash It confirms the flat price before work begins, and the instant quote on this page gives you a quick starting point.