Should stucco be power-washed before painting in Ottawa?

Yes — pressure washing is an essential step before painting stucco in Ottawa, but it needs to be done carefully. Too much pressure or the wrong technique can damage older stucco, blow out mortar joints, or force water deep into the wall assembly where it causes problems for weeks afterward.

How to Properly Pressure Wash Ottawa Stucco Before Painting

Why it's necessary: Ottawa stucco accumulates road salt residue, mineral deposits, pollution film, pollen, and biological growth (mildew and algae) that standard paint won't adhere to. Even stucco that looks clean to the eye usually has a film of contaminants that will cause paint to peel within 1–2 seasons. Skipping this step is a false economy — you'll be repainting years earlier than necessary.

Pressure settings: Use 1,500–2,000 PSI for stucco in good condition. For older or softer stucco (common on pre-1980s Ottawa homes), drop to 1,000–1,500 PSI. Newer acrylic stucco finishes can handle up to 2,500 PSI but there's rarely a reason to go that high. Use a 25-degree (green) or 40-degree (white) fan tip — never a zero-degree tip on stucco. Keep the nozzle 12–18 inches from the surface.

Dealing with Ottawa-specific issues:

• Road salt residue: Homes near busy roads (Carling, Bronson, Bank, Baseline) accumulate salt spray all winter. A detergent wash before pressure rinsing helps dissolve salt deposits that plain water misses.
• Mildew and algae: Very common on north-facing walls and anywhere shaded by Ottawa's mature tree canopy. Pre-treat with a mildew cleaner or TSP solution (1/2 cup per gallon of water), let it dwell 10–15 minutes, then rinse. If you paint over mildew, it will grow right through the new paint.
• Efflorescence: Those white powdery deposits are mineral salts leaching through the stucco. Pressure washing alone doesn't remove them — you need an efflorescence cleaner (muriatic acid diluted 10:1, about $15 per gallon) applied and scrubbed before rinsing. Wear proper PPE.

Timing considerations: Schedule washing for a stretch of warm, dry weather. You need a minimum of 48 hours of dry conditions after washing before priming — and in Ottawa's variable spring weather, budget 3–5 days to be safe. Never wash when overnight temperatures will drop below 5°C, as water trapped in the stucco texture can freeze and cause micro-spalling.

Cost: Professional pressure washing for painting prep runs $200–$500 for a typical Ottawa home (1,200–1,500 sq ft of stucco surface). This usually includes detergent treatment. Renting a pressure washer for DIY costs $75–$150 per day, but be aware that improper technique on stucco is a common source of damage claims.

What washing alone won't fix: Pressure washing removes surface contaminants but doesn't repair cracks, fill voids, or address delaminated stucco. Those issues need separate repair work after washing and before priming. Think of washing as step one of prep, not the entire prep process.

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Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• 613Bins
• RenoMotion Inc.
• Jaiko Cleaning Services
• Humble Homes - property maintenance
• Geerts Roofing Inc

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