Exterior Building Cleaning
Exterior Cleaning · exterior-cleaning
Siding material dictates the method. Vinyl, wood, stucco, and EIFS get soft washed — chemical cleaning at low pressure. Brick and masonry can handle pressure washing at 2,000–3,000 PSI. Any biological growth (mold, mildew, algae) gets a chemical treatment regardless of substrate. Identify the material before you pull the trigger.
Siding Material Identification and Method Selection
Vinyl siding gets soft washed to prevent water intrusion behind panels. Wood siding (cedar, pine, lap) is soft wash only — high pressure causes splintering and fiber damage. Brick and masonry handle pressure washing at 2,000–3,000 PSI without issue. Stucco and EIFS (synthetic stucco) are soft wash only — pressure cracks or dislodges the material. Fiber cement (HardiPlank) takes low-pressure washing at 1,300–1,600 PSI; avoid direct hits on seams. Metal siding (aluminum, steel) pressure washes at 1,500–2,500 PSI — watch for dents and paint damage. When in doubt, start with soft wash. You can always increase pressure if the surface can take it.
Chemical Treatment and Soft Wash Process
Soft washing kills and removes biological growth with chemicals rather than force. The primary agent is sodium hypochlorite (bleach) at 1–3% concentration for most residential work. Add a surfactant to improve adhesion and dwell time on vertical surfaces. Apply from bottom to top to prevent streaking, allow 10–15 minutes of dwell time, and monitor to ensure the solution does not dry on the surface. Rinse from top to bottom with low-pressure water under 500 PSI. Heavy mold or algae may require a second application before rinsing. Never mix sodium hypochlorite with other chemicals — dangerous gas reactions can occur. Store all chemicals in original containers and follow SDS guidelines.
Soft Wash Mix Ratios
Correct chemical concentration varies by surface. These ratios use sodium hypochlorite (SH) as the primary agent with a surfactant for adhesion. Verify your SH source concentration before mixing — supplier strength varies.
Soft Wash Mix Ratios
| Surface | SH Concentration | Surfactant | Rinse Required | Notes |
|---|---|---|---|---|
| Vinyl Siding | 1–2% | Yes — 4–6 oz per 5 gal | Yes — low-pressure rinse | Apply bottom to top; rinse top to bottom |
| Wood Siding (Cedar/Pine) | 1% | Yes — 4 oz per 5 gal | Yes — thorough rinse | Do not exceed 1%; wood absorbs chemical quickly |
| Stucco / EIFS | 1–2% | Yes — 6 oz per 5 gal | Yes — gentle rinse | Never pressure rinse stucco; use garden hose if needed |
| Brick / Masonry | 2–3% | Yes — 4–6 oz per 5 gal | Yes — medium rinse | Higher concentration OK for heavy biological growth |
| Concrete (Flatwork) | 3–4% | Optional | Yes — pressure rinse | Can follow up with pressure wash for embedded stains |
| Roof Shingles (Asphalt) | 3–4% | Yes — 6–8 oz per 5 gal | No — let rain rinse | Never pressure wash shingles; apply and walk away |
| Roof (Tile / Metal) | 2–3% | Yes — 6 oz per 5 gal | Optional — light rinse | Avoid pooling on metal; can cause discoloration |
| Fence (Wood) | 1–2% | Yes — 4 oz per 5 gal | Yes — thorough rinse | Rinse both sides; chemical can seep through boards |
| Gutters (Exterior) | 2–3% | Yes — 4 oz per 5 gal | Yes — rinse immediately | Black streaks may need additional oxidation remover |
| Awnings / Canvas | 0.5–1% | Yes — 2 oz per 5 gal | Yes — gentle rinse | Test a small area first; fabric can bleach unevenly |
Plant and Landscape Protection
Cleaning chemicals kill plants fast. Pre-wet all vegetation, shrubs, and grass within 10 feet of the work area before applying any chemical. Cover delicate plants with plastic sheeting or tarps during application. Rinse all vegetation thoroughly with clean water immediately after the job and apply a plant-safe neutralizer (diluted hydrogen peroxide) to anything exposed to bleach. Reposition downspouts or block drain paths if runoff could flow into garden beds. Schedule sensitive jobs during cooler parts of the day to reduce chemical evaporation stress on plants.
- Document any pre-existing plant damage before starting work
- Communicate plant protection measures with the customer upfront
Checklists
Exterior Building Cleaning Checklist
- Identify siding material and select pressure wash or soft wash method
- Inspect for loose siding, open seams, or damaged caulking
- Close all windows and doors on the building
- Pre-wet surrounding landscaping and cover sensitive plants
- Mix cleaning chemicals to appropriate concentration
- Apply chemical from bottom to top
- Allow proper dwell time (10–15 minutes)
- Rinse from top to bottom with appropriate pressure
- Inspect for missed areas or streaks and re-treat if needed
- Rinse all surrounding landscaping with clean water
- Perform final walk-through with customer