Soft washing your roof or siding isn't like pressure washing your driveway—get it wrong and you risk expensive damage. The difference between a skilled operator and a careless one can mean the difference between a clean roof that lasts 20 years and shingles stripped of their protective granules. Before hiring, you need to ask the right questions to separate professionals from cowboys.
Do They Understand Roof vs. Siding Differences?
A competent soft washing company should immediately explain that roofs and siding need different approaches. Asphalt shingles, for example, can't tolerate the same pressure or chemical mix that vinyl or fiber cement siding can handle. Ask them to walk you through their specific process for your roof material. If they give you a generic answer about their "standard soft wash," that's a red flag—you want someone who knows whether you have architectural shingles, three-tab, metal, or tile, and adapts accordingly.
What Cleaning Solutions Do They Use?
This is where chemistry matters. Ask directly: what's in their cleaning solution? Legitimate soft washing companies use biodegradable, surfactant-based cleaners (often containing sodium hypochlorite or similar algaecides) rather than harsh pressure alone. They should be able to name the product or at least describe the active ingredients. Avoid anyone who's vague about chemicals or claims they use only "water." Also ask how long the treatment lasts—quality soft wash jobs on roofs typically prevent algae and moss regrowth for 12–24 months, depending on climate.
Are They Insured and Licensed?
Request proof of liability insurance (at least $1 million coverage) and general business licensing. A slip off your roof or chemical damage to a neighbor's property can cost tens of thousands of dollars. Legitimate companies carry insurance because they work at height and handle chemicals. If they brush this off or claim they're "too small" to need it, walk away. Also ask if they're bonded—it's less common but adds another layer of protection.
What's Included in the Estimate and Timeline?
A concrete estimate should break down:
- Pre-treatment inspection
- Chemical application and dwell time
- Rinsing process
- Post-treatment sealing or protective coat (if applicable)
- Any repairs they'll flag but not perform
Ask how long the job takes. Most residential roof soft washes take 4–8 hours; siding jobs vary by square footage but typically run 6–12 hours. Get a timeline in writing. Also ask what happens if weather delays the work—will they reschedule at no charge? Good companies have policies for this.
Do They Offer a Warranty or Guarantee?
Reputable soft washing firms stand behind their work. Ask what they guarantee:
- Against damage (shouldn't be an issue with proper technique)
- Against incomplete cleaning (if algae or staining returns within 30 days)
- Against premature regrowth (some offer 90-day touch-ups included in the price)
A 12-month workmanship guarantee is standard. Anything less suggests they're not confident in their process.
Will They Inspect Your Roof Before Starting?
A professional should climb up or use a drone to assess your roof's condition before quoting. They're looking for loose shingles, damaged flashing, moss-covered valleys, or areas where soft wash solutions might seep into compromised spots. This inspection should be free and documented. If they quote over the phone without seeing the property, they're guessing—and guesses often lead to surprises.
What's the Price Range?
Soft washing a typical residential roof (1,500–2,500 sq. ft.) costs between $400–$900, depending on region, roof pitch, and contamination level. Siding runs $300–$800 for similar square footage. Steep roofs, heavy moss, or multiple stories push prices higher. Get at least three quotes—this helps you spot outliers. If someone's 60% cheaper than competitors, ask why; it might mean lower-quality materials or inexperience.
Frequently Asked Questions
Q: Can soft washing damage my shingles or siding? No, if done correctly. Soft washing uses low pressure (below 500 PSI) and chemical solutions to kill algae and stains rather than blast them away. Damage happens only when contractors use high-pressure or apply solutions improperly.
Q: How often should I soft wash my roof? Most homeowners benefit from soft washing every 18–24 months, depending on climate, shade, and humidity. If you live in a damp, forested area, annual washing may be worthwhile.
Q: Do I need to stay home during soft washing? You don't have to, but it's useful to be available so the crew can point out findings (loose flashing, damaged gutters) and answer questions. Most jobs take most of a day.
When you're ready to compare and hire, platforms like Mercoly help you find and vet trusted soft washing providers in your area side by side.