House Washing Made Safe: Siding, Stucco, and Painted Surfaces

Dust, salt haze, and desert algae accumulate quickly on building exteriors. In hot, sandy climates, the wrong washing approach can drive water behind siding, soften paint, or scar delicate stucco. This guide details soft washing for siding and stucco, safe PSI guidelines, and step-by-step methods that protect windows, sealants, and interiors.

Safety and Preparation to Prevent Water Intrusion

Exterior cleaning starts with controlling where water and chemistry go. Plan for shade or cooler hours to reduce chemical flash and streaking, and mask vulnerable points.

• Close windows and doors; check weatherstripping and weep holes.
• Cover door thresholds, outlets, and fixtures; use GFCI-protected circuits.
• Pre-wet plants and metals; set up gentle runoff paths away from thresholds.
• Work top-down in manageable sections to maintain wet edges.

Sensitive building elements to protect

• Light fixtures, doorbells, intercoms, and camera housings.
• Fresh paint (less than 14 days old), hairline stucco cracks, and open joints.
• Vents and soffits with gaps—approach from a downward angle only.

Soft Washing vs Pressure: Choose the Right Method

For most home exteriors, soft washing is the default. Pressure is a limited tool for rinsing only.

• Vinyl and fiber-cement siding: Soft wash application with low-pressure rinse.
• Stucco (traditional or acrylic): Soft wash with controlled dwell; low-pressure rinse to avoid surface erosion.
• Painted masonry or wood cladding: Soft wash and extremely gentle rinse; avoid lifting paint or forcing water behind boards.

Safe PSI and nozzle guidance

• Application pressure: typically under 100 PSI via soft-wash pump or low-pressure nozzle.
• Rinse pressure: stay well under 800 PSI on siding; 400–600 PSI on stucco and painted surfaces.
• Use 40° or 25° tips; keep generous standoff. Never use turbo/rotary nozzles on walls.

Roof-Safe Chemistries Adapted for Walls

Walls often carry a mix of dust, soot, algae, and hand oils near entries. Use a balanced solution and protect surrounding finishes.

• Base cleaner: Sodium hypochlorite (SH) at 0.5–1.0% on surface for organic films, paired with a neutral surfactant for cling and even wetting.
• Painted surfaces: Favor the low end of the range; test in an inconspicuous spot.
• Rust, sprinkler stains: Oxalic/ascorbic spot treatments; rinse and neutralize.
• Grease or hand marks: Mild alkaline degreasers; agitate with a soft brush.

Always keep solutions wet during dwell—heat accelerates evaporation and can cause streaks. Rinse metals, glass, and plants thoroughly.

Detailing windows and frames

Avoid saturating window edges. Mist glass with clean water before and after chemical exposure to minimize spotting. For oxidized aluminum frames, test gently—do not rub aggressively, which can create bright spots.

Step-by-Step House Washing Workflow

1. Inspect and stage

• Identify cladding type, cracks, failing sealants, or chalking paint.
• Move furniture and cover electronics; ensure safe ladder footing.

2. Dry prep

• Blow off dust and cobwebs with a blower or soft brush.
• Remove wasp nests with care; avoid smearing residues on porous stucco.

3. Chemical application

• Apply solution from bottom-up for porous stucco to reduce streaking; for sealed siding, top-down is fine.
• Maintain even coverage and re-mist to prevent drying in sun or wind.

4. Agitation (as needed)

• Use a soft-bristle brush on stubborn areas, under eaves, and around handles and switches.

5. Low-pressure rinse

• Rinse top-down with a wide-angle tip, keeping distance and avoiding upward angles at laps and soffits.
• Flush weep holes lightly to clear loosened dust without flooding cavities.

6. Detailing and spot treatments

• Address rust drips or sprinkler lines with dedicated remover; neutralize and rinse.
• Squeegee or towel-dry glass to prevent mineral spotting in hard water areas.

Common Mistakes That Cause Damage

• Spraying upward under siding laps or into soffit vents.
• Allowing SH to dry on hot stucco—leads to uneven bleaching and residue.
• Using high PSI that etches stucco or lifts paint.
• Neglecting to rinse metals and windows, causing oxidation or spotting.
• Rushing in full sun; always manage dwell and keep a wet edge.

When to Call a Professional

• Hairline stucco cracking that may require patching before washing.
• Heavy oxidation on colored aluminum or chalking on paints.
• Multi-story homes needing safe access and controlled overspray.
• Sensitive landscaping or water reclamation requirements.

Pros bring proportioning systems for precise dilutions, low-pressure rinse strategies, and staging to protect interiors while speeding up the process.

Maintenance Cadence for Hot, Sandy Regions

• Light dusting or gentle rinses monthly in windy seasons.
• Annual soft wash for shaded elevations; every 18–24 months for sun-baked walls.
• Promptly clean sprinkler spotting to avoid permanent mineral bonding.
• Reseal or repaint per manufacturer intervals to maintain cleanability and UV protection.

A careful, chemistry-led approach keeps siding, stucco, and painted walls clean and intact—without risking leaks or surface damage.