How to Clean Exterior Bricks? | Safe, Step-by-Step Methods

Most exterior brick doesn’t need harsh chemicals or expensive equipment. A bucket of warm water, a squirt of dish soap, and a stiff brush handle the majority of grime, mold, and dirt buildup. The trick is knowing when to stop—aggressive methods like pressure washing or acid treatments can permanently scar the masonry. Here’s the safe sequence that works across typical residential and commercial brickwork, plus the mistakes that cause lasting damage.

What You Need Before You Start

Gather your supplies first so the job goes fast and you’re not leaving cleaner on the brick while you hunt for tools. You’ll need a stiff bristle brush (a long-handled one saves your back), a bucket, mild detergent or dish soap, and a garden hose with a spray nozzle. A pump sprayer helps apply cleaning solution evenly across larger walls.

For tougher stains like rust or heavy efflorescence, you may need a dedicated cleaner. The Brick Industry Association recommends choosing the gentlest effective method for the job at hand. If you’re comparing products, our tested roundup of brick cleaners covers which formulations actually work without damaging masonry.

The Step-by-Step Cleaning Method

The general procedure is simple: wet the brick first, apply the cleaner, scrub, and rinse thoroughly. Here’s the order that gets results without causing damage.

1. Wet the brickwork fully. Use a garden hose to saturate the wall from top to bottom. Damp brick absorbs less cleaning solution, which prevents the chemicals from penetrating too deep and keeps the cleaner working on the surface where the dirt is.
2. Mix your cleaning solution. Add a small amount of mild detergent or dish soap to a bucket of warm water. This is strong enough for most exterior grime, mold, and mildew.
3. Apply the solution. Working from the bottom of the wall upward—this prevents dirty runoff from streaking over already-cleaned brick—apply the solution with a brush or pump sprayer.
4. Scrub with a stiff bristle brush. Work the brush in a circular motion, focusing on stained areas. For rough-textured brick, scrub a little harder; for smooth brick, ease off to avoid scuffing the surface.
5. Rinse thoroughly with clean water from top to bottom. This washes away both the dirt and the cleaning solution. Never let the cleaner dry on the brick—it can leave a residue that’s harder to remove than the original grime.

One full pass usually handles a year’s worth of typical dirt. For stubborn buildup, repeat the process rather than switching to a harsher chemical.

What Not to Do

The fastest way to ruin brick is to reach for the wrong tool. Wire brushes and metal scrapers scratch the surface and can gouge the mortar joints. Harsh acids cause even worse damage. The Brick Industry Association specifically warns against unbuffered muriatic (hydrochloric) acid and hydrofluoric acid on brickwork—these dissolve the surface of the brick and leave permanent discoloration and spalling.

GoBrick’s maintenance guidance echoes that warning, noting that muriatic acid should not be used even in diluted form. Pressure washing is another common mistake. GoBrick advises leaving pressurized water to experienced professionals because improper power washing can permanently damage masonry by eroding the mortar and scoring the brick face. If you must use a pressure washer, keep the nozzle at least 12–18 inches from the wall with a wide fan pattern—but know that a brush and hose is safer for the brick and often just as effective.

Dealing With Stubborn Stains

Sometimes plain detergent isn’t enough. For rust stains or heavy efflorescence, the General Services Administration’s technical procedure outlines a stronger approach. Wet the masonry first, then apply a solution of 1 lb (0.45 kg) of oxalic acid crystals dissolved in 1 gallon (3.79 L) of water, or a mix of 9 parts water to 1 part muriatic acid for certain treatments. Scrub with a stiff bristle brush and let it dwell for 5 to 10 minutes before rinsing thoroughly.

These acid treatments work, but they demand respect. The GSA procedure is written for trained masonry technicians working on historic structures—the chemical strength that strips rust stains will also burn skin and kill nearby plants.

Before applying any acid-based cleaner, take the safety steps seriously:

• Protect nearby plants and grass with plastic sheeting; acid runoff will kill vegetation.
• Cover windows, outlets, fixtures, and metal trim to prevent staining and corrosion from overspray.
• Wear rubber gloves, safety goggles, and long sleeves.
• Test the solution on a small, inconspicuous patch of brick first.

If the stain is still there after an acid treatment, stop. The residue may be locked into the brick itself, and further chemical attack will only degrade the masonry.

Keeping Brick Clean Longer

After you’ve done the work, simple habits extend the results. Keep gutters and downspouts clear so water doesn’t cascade down the wall and drag dirt with it. Trim bushes and vines back from the brick so leaves don’t accumulate and trap moisture against the surface. When you see a stain form, treat it quickly—surface dirt is easy to brush off, but once it’s baked in by sun and weather, it takes a chemical treatment or professional equipment to remove.

The most important rule applies from the first wash: gently does it. A soft approach with soap and a brush handles the overwhelming majority of brick-cleaning jobs, and it never risks the one thing you can’t replace—the brick itself. When tougher problems arise, concrete steps in the right order work better than a harsh chemical used wrong.