Soft Washing Brick: The Safe Way to Clean Your Home's Exterior

Brick homes are a staple of Kitchener-Waterloo neighbourhoods, and they look stunning when clean. But many homeowners make a costly mistake: renting a pressure washer and blasting away years of grime, not realizing they're also destroying the mortar that holds everything together. Here's why soft washing is the only sensible approach for brick — and how the process works.

Why Pressure Washing Damages Brick

Brick itself is fairly hard and can tolerate moderate pressure. The problem is the mortar joints. Mortar is significantly softer than brick, and at pressures above 1,500–2,000 PSI, it begins to erode. At the 3,000 PSI that many consumer pressure washers reach, mortar can be visibly dislodged in a single pass.

The damage isn't always obvious immediately. Sometimes the mortar simply becomes porous and weakened — you can't see it with the naked eye, but water now infiltrates freely. In Ontario's climate, that infiltrating water freezes in winter, expands, and accelerates spalling on the brick face itself. Within a few seasons, you'll see chunks of brick surface flaking away.

Spalling is the term for this brick face failure, and it's expensive to repair. Tuckpointing (mortar replacement) and brick replacement can run into thousands of dollars for a full facade. Aggressive pressure washing on older brick homes — particularly those built before 1950 using softer historical brick — can cause immediate, irreversible surface damage in a single session.

There's also a risk with older brick homes that have been painted or sealed. High-pressure water can blast off paint coatings, which then have to be stripped and re-applied. This is especially relevant in Cambridge and parts of Kitchener, where you'll find many pre-war brick homes.

What Is Soft Washing?

Soft washing is a cleaning method that uses very low water pressure — typically under 500 PSI, and often as low as 60–100 PSI — combined with a specially formulated cleaning solution to do the work that pressure alone cannot safely accomplish.

The key insight is this: pressure is a mechanical cleaning method. It works by physically blasting surface material away. Soft washing is a chemical cleaning method — the cleaning solution breaks down and kills organic growth (mould, algae, mildew, lichen) at the cellular level, then the gentle rinse carries it away.

The result is cleaner for longer, because the cause of the staining — the living organisms — has been eliminated rather than just temporarily blasted off. With pressure washing, algae and mould regrow quickly because the root structures remain in the pores of the brick. Soft washing kills those roots.

The Soft Washing Solution: What's Actually in It

Professional soft washing solutions are primarily composed of two components: a biocide and a surfactant.

The biocide is typically sodium hypochlorite (bleach) at a concentration appropriate for the surface being cleaned. For brick, this is typically a diluted solution — around 1–3% sodium hypochlorite concentration. This is enough to kill mould, algae, mildew, lichen, and bacteria on contact without damaging the brick or mortar.

The surfactant (a wetting agent, essentially a specialized soap) does two important jobs: it helps the cleaning solution penetrate into the pores of the brick for deeper cleaning, and it creates a foam or "cling" that keeps the solution in contact with the surface long enough to be effective rather than simply running off.

Professional soft washing companies mix these solutions on-site in proportions matched to the specific surface, level of contamination, and environmental conditions. A heavily mould-contaminated north-facing brick wall needs a different treatment than a lightly soiled south-facing wall.

Some companies add neutralizers to the rinse water to prevent any bleach residue from affecting nearby plants or landscaping. This is particularly important for brick homes with mature foundation plantings — a common feature in Waterloo Region's established neighbourhoods.

The Soft Washing Application Process

A professional soft wash of a brick exterior follows a methodical process:

1. Pre-rinse inspection: The technician examines the mortar condition, checks for damaged or loose brick, and identifies any areas with particular concentrations of biological growth, efflorescence, or rust staining.
2. Pre-wet surrounding vegetation: Before any cleaning solution is applied, nearby plants, shrubs, and garden beds are thoroughly pre-wetted. This dilutes any solution that drips or drifts onto them.
3. Apply cleaning solution: The soft wash solution is applied to the brick surface using a low-pressure pump sprayer. Coverage is thorough, ensuring the solution reaches all mortar joints and recessed areas. The solution is applied bottom to top — starting at the top and letting solution run down the dirty lower sections creates uneven cleaning and can cause streaking.
4. Dwell time: The solution is left on the surface for 5–15 minutes (longer for heavy biological growth). During this time, the sodium hypochlorite is actively killing the organic material embedded in and on the brick.
5. Rinse: A thorough, low-pressure rinse removes the cleaning solution along with all loosened organic material. The pressure stays under 500 PSI, protecting the mortar completely.
6. Post-rinse plant flush: Surrounding vegetation is rinsed thoroughly with clean water as a final precaution.

"We've cleaned brick homes in Kitchener-Waterloo that haven't been touched in fifteen years. After a proper soft wash, they look like new construction — and the mortar is completely intact."

— David, D&D Home Services Co-Founder

Efflorescence vs. Mould: Different Problems, Different Solutions

Two of the most common issues on brick exteriors in Ontario are often confused because they can both appear as discolouration, but they require completely different treatments.

Efflorescence is the white, chalky, salt-like deposit that appears on brick surfaces. It's caused by soluble salts migrating from within the brick or mortar to the surface as water moves through and evaporates. Efflorescence is very common in Ontario due to our wet springs and the salt-laden winter environment. It is not harmful to the brick structurally, but it is visually prominent and indicates moisture is moving through the wall.

Soft washing solution does not effectively remove efflorescence — sodium hypochlorite won't dissolve mineral salt deposits. Efflorescence requires a different treatment: a diluted muriatic acid or specialized efflorescence remover applied carefully, then thoroughly rinsed. This is a treatment that requires caution — muriatic acid can etch mortar and brick if not properly diluted and rinsed.

Green, black, or brown organic growth (mould, algae, mildew, lichen) is biological in nature and is exactly what soft washing is designed to eliminate. Black streaking on brick is almost always Gloeocapsa magma algae. Green growth is typically algae or moss. Soft washing at the appropriate concentration kills all of these and prevents rapid regrowth.

Many brick homes will have both issues simultaneously — especially on north-facing walls and in shaded areas. A professional will treat each issue appropriately rather than applying a one-size-fits-all approach.

Drying and Results: What to Expect

Soft-washed brick typically dries within 2–4 hours on a dry, sunny Ontario day. The full brightening effect becomes most visible once the brick has completely dried — wet brick appears darker and hides the cleaning results temporarily.

In most cases, homeowners are pleasantly surprised by the difference. Brick that had appeared permanently darkened by decades of organic staining returns to something close to its original colour. The mortar joints clean up particularly well and provide a visual definition that was completely lost under years of grime.

Organic growth will eventually return — that's simply the nature of an exterior surface exposed to Ontario's humid summers and wet falls. However, because soft washing kills the growth at the source, results typically last 2–4 years before re-treatment is needed, significantly longer than the 6–12 months that pressure washing provides before regrowth returns.

When DIY Is Risky and When to Call Professionals

For newer brick homes (post-1980) with a standard clay brick and good mortar condition, a careful DIY approach with a garden pump sprayer and diluted sodium hypochlorite solution is possible for homeowners comfortable with mixing chemicals safely. The key rule: never exceed 500 PSI for any rinsing, and test a small hidden area first.

However, we recommend professional soft washing for:

• Older homes (pre-1970): Softer historical brick and aged mortar need expert assessment before any cleaning.
• Painted brick: Painted surfaces require specific solution concentrations and technique to avoid paint damage.
• Multiple-storey homes: Safe access to upper sections of a brick facade requires professional ladders and equipment.
• Heavy mould or lichen infestations: These require stronger solutions and potentially multiple applications — chemical concentrations that are safer in professional hands.
• Brick with visible mortar damage: Tuckpointing should be done before cleaning, and a professional will identify these areas during inspection.
• Heritage or historic homes: Many older brick homes in Cambridge and Kitchener require specialized care. Some heritage districts have specific guidelines on cleaning methods.

Our professional soft washing service covers brick homes throughout Kitchener, Waterloo, Cambridge, and Guelph. We inspect the brick condition before quoting, use the appropriate solution concentration for your specific situation, and protect your landscaping throughout the process.

D&D Home Services TeamExterior Cleaning Experts

D&D Home Services is Kitchener-Waterloo's trusted exterior cleaning company serving Kitchener, Waterloo, Cambridge, and Guelph.