Pressure Washing Tips — The Honest Homeowner's Guide (2026)

Every spring we get calls from Oakville, Burlington, Milton, and Mississauga homeowners who rented a unit from Home Depot, gave it a good go on Saturday morning, and ended up denting vinyl siding, etching concrete, or blowing pointing out of their brick. Pressure washing is more finicky than it looks, and the mistakes are expensive to fix.

This is the honest guide — what to do, what not to do, and when to hand it off.

The single most important concept: matched pressure

Every surface has a maximum safe pressure, a preferred detergent, and a distance + angle range. Get any of those wrong and you damage the surface. Here's the cheat sheet:

Surface	Max PSI	Tip	Distance	Detergent
Vinyl siding	500	40° fan	12–18"	Soft-wash sodium hypochlorite + surfactant
Fiber cement	500	40° fan	12–18"	Soft-wash
Aluminum siding	500	40° fan	12"	Soft-wash
Engineered wood siding	500	40° fan	18"	Mild soft-wash
Painted wood	800	40° fan	18"	Oxygen-based brightener
Pressure-treated deck	1200	25°	10"	Wood-safe detergent
Cedar deck	800	40°	12"	Oxygen brightener (no bleach!)
Composite decking	1500	25°	8"	Manufacturer recommended
Concrete driveway	3000	15° or surface cleaner	6"	Degreaser for oil, standard for organic
Interlock pavers	3000	Surface cleaner	6"	Biocide for moss, muriatic for efflorescence
Stamped concrete	1500	25° or soft brush	12"	pH-neutral (no acid!)
Brick (modern)	1500	25°	10"	Soft-wash
Brick (pre-1960)	500	40°	12"	Soft-wash only
Stucco	500	40°	12"	Soft-wash
Asphalt	DON'T	—	—	—

The five mistakes we see every year

1. Using high pressure on vinyl siding

The #1 mistake. A homeowner sees a stubborn algae stain on the north side and thinks "more pressure will fix it." High pressure doesn't lift biological staining — detergent chemistry does. High pressure on vinyl dents panels, forces water behind the siding, and creates long-term mold problems inside the wall cavity.

Right approach: Soft wash with sodium hypochlorite + surfactant blend. 8–12 minute dwell time. Low-pressure rinse.

2. Spraying upward into siding laps

Vinyl, fiber cement, and engineered siding are all installed overlapping downward. Spraying upward pushes water UP into the laps, which the system was never designed to handle. Three months later you have mold inside the wall cavity.

Right approach: Always spray downward or at a 45° downward angle. Never upward.

3. Using bleach on cedar or stained wood

Bleach (sodium hypochlorite) is the right detergent for vinyl and algae. It's the wrong detergent for cedar, redwood, or stained softwood. It kills the wood fibres and leaves a dull grey that won't re-stain evenly.

Right approach: Oxygen-based brighteners (percarbonate) for wood. Or a dedicated wood-safe brightener.

4. Pressure washing interlock without re-sanding

Pressure washing an interlock driveway at 3000 PSI is the right technique — but it displaces the joint sand. If you don't re-sand after cleaning, your driveway is now less stable than before you started. Weeds will come back twice as fast.

Right approach: Clean → dry 24 hours → install polymeric sand → activate with mist. Two visits minimum.

5. Not pre-wetting vegetation

Sodium hypochlorite at cleaning dilution is hard on plant leaves. Pre-wetting the leaves gives them a water-film barrier and prevents detergent uptake.

Right approach: Pre-wet all shrubs, flowers, and grass within 10 feet of the work area. Tarp sensitive specimens. Rinse thoroughly when done.

DIY vs hire — how to decide

DIY makes sense for:

• Single-section driveway (concrete) if you're physically capable
• Small deck or patio
• Furniture and outdoor equipment

Hire a professional for:

• Second and third storey siding (fall risk)
• Whole-house siding cleaning (chemistry + even coverage are hard)
• Interlock (unless you're prepared for the multi-visit process)
• Heritage homes (soft brick, limestone, stucco)
• Anything where you're unsure of the right pressure

What a real professional service should include

• Written, fixed-scope quote BEFORE arrival
• Property walk-through before work starts
• Surface-matched pressure and detergent
• Plant protection
• Appropriate detergent chemistry (not just a generic cleaner)
• 18-inch rotary surface cleaner for concrete and interlock
• Rotary surface cleaner for concrete/interlock
• Soft-wash capability for vinyl/fibercement
• Hot water for oil/grease stains (diesel burner units)
• Post-rinse and neutralize
• Walk-through and sign-off
• Before/after photos
• Insurance ($2M general liability minimum)

If a quote lacks any of the above, keep shopping.

When to schedule

Spring (April–June): Winter salt, road grime, pollen. Our busiest season. Summer: Driveway cleanings and deck prep for staining. Fall (September–October): Post-summer dust + winter prep. Winter: Off-season in the GTA; interior window cleaning and planning consults continue.

Bottom line

Pressure washing is a legit maintenance activity with real benefits — curb appeal, material longevity, health (mold/algae). Done wrong it causes thousands in damage. Done right, it's one of the best value-per-dollar home maintenance spends.

If you're going to DIY, read the table above twice. If you're going to hire, look for the checklist. And if you live in Oakville, Burlington, Milton, or Mississauga and want a written quote, we're happy to help.