Pressure washing safety

Chemicals. Soft washing is a chemical process. Today's Homeowner's mixing guidance uses a quarter gallon of chlorine to a gallon of water (roughly 1:9) with a 25 to 30 minute dwell, or a quarter gallon of bleach to a gallon of water with a 15 to 30 minute dwell, and is blunt about the protective equipment needed because the chemicals can cause second- to third-degree burns. ARMA's roof method uses a 50:50 mix of laundry-strength liquid chlorine bleach and water and advises appropriate PPE plus precautions to protect landscaping.

Plants. Bleach solution running off a roof or wall lands on whatever is below it. Today's Homeowner's practical advice is to over-hydrate plants before cleaning so they absorb less of the solution. A professional crew should be pre-wetting, covering and rinsing plants as a matter of routine — ask what they do.

Heights. Most roof-cleaning injuries are falls, not chemical burns. Combine a wet surface, a bleach solution and a ladder and you have a genuinely dangerous job. Malarkey also notes that excessive walking on shingles dislodges granules and prematurely ages them — so even a successful DIY roof clean can cost you roof life.

The machine. A pressure washer stream can injure skin and drive contamination into a wound. Never point it at a person, never use it from an unstable ladder, and be cautious near electrical service entries, outdoor outlets, light fixtures and meters. Polymeric Exteriors guidance specifically cautions around windows, doors, electrical wiring and plumbing.

Cold weather. There's a safety and damage angle here. NPS guidance advises that water cleaning of masonry should never be done in cold weather or when frost is likely, because water in the masonry can freeze and cause spalling and cracking, and notes a masonry wall may take over a week to dry.

How to choose

Treat soft wash solution as a hazardous chemical

Gloves, eye protection, long sleeves, boots. Today's Homeowner warns these solutions can cause second- to third-degree burns.

Ask the crew about plant protection before they mix

Pre-wetting, covering and rinsing. ARMA advises protecting landscaping from the bleach solution — a good contractor already does this.

Hire out roof work

Wet shingles, a ladder and bleach is not a DIY combination. And walking the roof damages granules even when nothing goes wrong.

Keep the stream away from people, wiring and openings

Guidance for siding specifically cautions around windows, doors, electrical wiring and plumbing. The same applies to meters, fixtures and vents.

Don't wash masonry in freezing weather

NPS advises against water cleaning in cold conditions or before a frost, because trapped water freezing causes spalling and cracking.