Brick House Washing with Safe Low Pressure — How to Clean Brick Without Damage

By Jason Geiman, King of Pressure Wash | 142,000+ views on YouTube

Brick is one of the most common exterior surfaces you’ll encounter as a pressure washing operator, and it’s also one of the easiest to damage if you don’t know what you’re doing. High pressure on brick can blast away mortar, chip the brick face, and force water deep into the wall cavity where it doesn’t belong. The right approach is low pressure with the right chemical — and the results are better than anything you’ll get by blasting it.

I’ve been washing brick homes professionally for over 15 years, and I can tell you that the key to a great-looking brick house isn’t more pressure — it’s the right technique. In this post, I’ll walk you through how to safely wash a brick home using low pressure methods that protect the surface while delivering professional results.

Why High Pressure Damages Brick

Brick and mortar are more fragile than most people realize. The mortar joints between bricks are especially vulnerable — they’re softer than the brick itself and can be eroded or blown out by high-pressure water. Once the mortar is compromised, water can get behind the brick and cause serious structural issues including mold, efflorescence (white salt deposits), and even wall failure over time.

The brick face itself can also be damaged. Many bricks have a harder, fired surface layer that protects the softer interior. High-pressure water can chip away that surface layer, exposing the softer brick underneath to weather and moisture damage. Once that protective layer is gone, the brick deteriorates much faster.

Even if the damage isn’t immediately visible, forcing high-pressure water into brick drives moisture deep into the wall. This moisture can take weeks to dry out, and in the meantime it can cause mold growth, paint bubbling on interior walls, and other moisture-related problems.

The Low-Pressure Method for Brick

Step 1: Pre-wet the brick

Before applying any chemical, wet the brick surface with plain water using low pressure. This prevents the brick from absorbing too much chemical and helps the solution spread evenly across the surface. Start from the bottom and work your way up to prevent streaking from dirty water running down dry brick.

Step 2: Apply your cleaning solution

Use a downstream injector, X-Jet, or 12-volt pump to apply a mild sodium hypochlorite (bleach) solution with a surfactant. The chemical does the cleaning work — not the pressure. Apply from the bottom up so the solution doesn’t run down and streak the dry brick below. You want an even coat across the entire surface.

Step 3: Let it dwell

Give the chemical 5-10 minutes to work. You’ll see the algae, mildew, and dirt starting to break down and lighten. Don’t let the solution dry on the brick — if it’s a hot day, mist the surface with water to keep it wet. The surfactant helps the chemical cling to the surface and stay active longer.

Step 4: Rinse with low pressure

Rinse the brick from the top down using a wide fan tip at low pressure — 500 to 800 PSI is plenty. You’re just washing away the chemical and the loosened grime. The chemical already did the hard work. A 40-degree nozzle at a reasonable distance from the wall gives you a gentle, wide rinse pattern that cleans without damaging the mortar.

Chemical Selection for Brick Cleaning

Sodium hypochlorite (bleach) is the go-to chemical for most brick cleaning jobs. It kills algae, mildew, mold, and other organic growth on contact. For most residential brick cleaning, a mild downstream mix is all you need. The exact strength depends on how dirty the brick is and what kind of growth is on it.

Add a surfactant to your bleach mix. The surfactant helps the chemical cling to the vertical brick surface instead of running off immediately. This gives the bleach more dwell time to work and produces a more even clean. Use a bleach-stable surfactant designed for pressure washing.

For heavy staining beyond organic growth — things like rust stains, efflorescence, or heavy mineral deposits — you may need a specialty brick cleaner. These are typically acid-based products that dissolve mineral deposits. Be very careful with acid-based cleaners on brick — they can etch the surface if used improperly. Always follow the manufacturer’s instructions and test on an inconspicuous area first.

Common Mistakes When Washing Brick

Using too much pressure. This is the biggest mistake and the one that causes the most damage. You do not need 3,000-4,000 PSI to clean brick. Let the chemical do the work and rinse at low pressure. If the chemical doesn’t remove the stain, the answer is stronger chemical or more dwell time — not more pressure.

Not pre-wetting the surface. Applying chemical to dry brick allows the chemical to soak deep into the pores. Pre-wetting fills the pores with clean water so the chemical stays on the surface where it’s needed.

Applying chemical from the top down. This causes the chemical to run down over dry brick below, creating streaks. Always apply chemical from the bottom up. Rinse from the top down.

Letting the chemical dry on the surface. Dried chemical can leave white residue or discoloration on the brick. Work in manageable sections and keep the surface wet until you rinse.

Ignoring the mortar condition. Before you start, inspect the mortar joints. If the mortar is already crumbling, loose, or deteriorating, even low pressure can dislodge it. Let the homeowner know about the mortar condition before you begin so there are no surprises.

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