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What is soft washing, and how is it different from pressure washing?
Soft washing cleans roofs and siding with a bleach solution, sodium hypochlorite mixed with water and a surfactant, sprayed at low pressure, left to dwell, then rinsed. The bleach kills the algae behind black roof streaks and the moss; pressure washing relies on water force, which strips granules off shingles. Everflo's soft-wash pumps top out at 60 to 70 PSI. Ask what mix strength the cleaner uses on your surface and how they protect your plants.
What is in a soft-wash mix?
Household bleach (6% sodium hypochlorite), a soft-wash surfactant and water. Everflo's chart mixes it to 1% for siding and screen enclosures, 2% for fences and decks, and 3% for roofs, brick, stucco and concrete, and says never to exceed 3% in its sprayer. SoftWash Systems' chart runs from 1% for vinyl siding and soffits up to 4% for shingle roofs. ARMA's homeowner recipe is half laundry bleach, half water.
The surfactant makes the mix cling, and SoftWash Systems says its additive lets the bleach clean at a lower concentration. Everflo has the mix dwell about 10 minutes without drying; ARMA allows 15 to 20 minutes before a low-pressure rinse. If a cleaner uses one mix for roof and siding alike, ask why.
How low is soft-wash pressure?
Everflo's soft-wash pumps are rated at 60 or 70 PSI maximum, depending on the model. The chemical does the cleaning; the pump only has to deliver it. That is why shingle roofs get soft washed: ARMA, the asphalt shingle makers' association, says never to clean a shingle roof with a pressure washer, because it causes granule loss and very likely premature failure of the roof.
Everflo's instructions spray roofs top to bottom and siding bottom to top, in 10-foot-wide sections, applying only enough to wet the surface, then rinse from the top down until no suds are left. Everflo also says its mix is not for painted wood. Ask what the cleaner uses on painted trim and what pressure they rinse with.
Will soft washing kill my plants?
Bleach runoff burns the plants it soaks into, so the protection is plain water. Everflo's steps soak every plant the mix could reach before spraying, soak the ground around the downspouts when a roof has gutters, and rinse the plants again afterward. ARMA also calls for protecting the landscaping from the bleach solution. Ask who does the soaking and rinsing, and where the roof runoff goes.
Everflo has outlets and light fixtures covered and decorations taken down before spraying. Move pots, cushions and the grill before the crew arrives. If a painted surface or a color worries you, ask for a test spot first; Everflo calls for testing the mix somewhere out of sight.
What does a soft wash cost, and what should the quote list?
HomeGuide puts washing a house exterior at $170–$360 per job and Angi at $213–$449 per job; Angi names the home's size, the number of stories and the siding material as what moves the total. Ask whether that price is a soft wash of the siding only, and whether the roof, gutter faces, windows and driveway are separate lines. The quote should name each surface and its mix strength.
Send this with photos: Please quote a soft wash of the siding and attached garage shown here. What mix strength will you use on this siding, how will you protect the plants, and does the price include the porch ceiling and the outside of the windows? Please list any roof treatment or return visit separately.
Frequently asked questions
How long does a soft wash last?
Until algae blows back in. ARMA says the spores travel on wind and animals from roof to roof, which is why whole neighborhoods streak, and shade and damp debris bring it back sooner. Trim overhanging branches and keep the roof and gutters clear.
Why is my roof still streaked after a soft wash?
The algae is dead but not gone yet. ARMA says it washes away with the rains that follow, and moss loosens over time and comes off with a leaf blower. Heavy moss can take more than one treatment; ask whether a second one is in the price.
Does pressure washing void a shingle warranty?
Read the warranty's exclusions before anyone touches the roof, and hire a cleaner who soft washes shingles. Get the method and the mix strength written into the quote, so you have a record if you ever file a claim.
Sources
- Asphalt Roofing Manufacturers Association: Algae and moss cleaning · Checked
Bleach and water treatment, dwell time, a low-pressure rinse, no pressure washers on shingles, plant protection and why algae returns.
- SoftWash Systems: Green Wash 6X · Checked
A maker's bleach-compatible surfactant and its recommended bleach strengths by surface.
- Everflo: Soft-wash pump manual · Checked
Mix ratios by surface, dwell time, spraying and rinsing steps, protecting plants (pages 19–21) and maximum pump pressures of 60–70 PSI (page 27).
- HomeGuide: pressure washing prices · Published · Checked
Driveway washing by cleaned area and house washing by the job, with different prices for different surfaces.
- Angi: house pressure washing prices · Published · Checked
House pressure washing by the job, with area, stories and surface material affecting the total.
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