Hiring someone to clean your roof feels straightforward until something goes wrong. Stripped shingle granules, voided warranties, damaged landscaping, streaked siding, and results that last six weeks instead of two years are all outcomes that homeowners deal with after hiring the wrong company. The roof is one of the most expensive components of a home, and cleaning it incorrectly can shorten its life rather than extend it.
The problem is that exterior cleaning is a low-barrier-to-entry industry. Anyone with a pressure washer and a truck can list "roof cleaning" as a service. That does not mean they understand the difference between soft washing and pressure washing, know what cleaning solutions are appropriate for different roofing materials, or have the insurance to cover damage when something goes wrong.
These seven questions help you separate the companies that know what they are doing from the ones that will learn on your roof.
1. What method do you use to clean roofs?
This is the most important question, and the answer should be specific.
The correct answer is some version of soft washing: a low-pressure application of cleaning solution that kills biological growth without mechanically disturbing the shingles. The solution does the work. The rinse just carries the dead growth away.
Answers that should concern you:
- "We pressure wash it." Pressure washing asphalt shingles strips granules, forces water under shingle edges, and is explicitly prohibited by major manufacturers.
- "We use a low-pressure setting on the pressure washer." A residential pressure washer on a low setting still delivers more force than a soft-wash system. The delivery method matters, not just the PSI number.
- "We scrape the moss off first and then treat." Manual scraping of established moss damages the shingle surface beneath it. Light brushing of very loose debris is different from aggressive scraping, and the distinction matters.
The answer you want includes the words "soft wash" or "low-pressure treatment" and describes a process where chemical application comes before any rinsing.
2. What cleaning solution do you use, and is it safe for my landscaping?
A professional roof cleaning company should be able to name the type of cleaning solution they use, explain how they protect surrounding plants, and describe their rinse process after application.
Standard professional roof cleaning uses a sodium hypochlorite-based solution diluted to an appropriate concentration for roofing. This is effective against moss, algae, and lichen. It can damage plants if not managed correctly, which is why pre-wetting landscaping, controlling application, and rinsing foliage afterward are all standard practice for a competent crew.
Concerns:
- A company that cannot name their cleaning product or says "it's proprietary" without further explanation
- A company that does not mention plant protection at all
- A company that uses unusually strong concentrations to speed up the process
Ask specifically what happens to plants and landscaping during and after the cleaning. The answer should describe a deliberate, multi-step protection process, not a dismissive "it'll be fine."
3. Are you insured, and can you provide a certificate?
This question matters more for roof cleaning than for most other home services because the risk of damage is real and the stakes are high.
A roof cleaning company should carry:
- General liability insurance that covers damage to your property
- Workers' compensation insurance that covers their crew if someone is injured on your property
Ask for a certificate of insurance, not just a verbal confirmation. Any legitimate, insured company can provide this quickly. A company that hesitates, makes excuses, or says they "don't need it" is telling you something important.
If an uninsured worker is injured on your roof or an uninsured company damages your shingles, the liability can fall back on you as the property owner.
4. How long will the results last, and what affects that?
This question tests both honesty and local knowledge. A company with experience cleaning roofs in the Hillsboro and west Portland metro area should give you a specific, realistic answer based on your property's conditions.
Honest answers typically sound like:
- "One to three years, depending on shade and tree cover."
- "Two years is typical for most homes in this area. Heavily shaded roofs may need attention sooner."
Answers that should raise a flag:
- "It'll never come back." Moss and algae return in any Pacific Northwest environment where shade and moisture persist. Permanent results are not realistic.
- "Five years, guaranteed." Very few roofs in this climate stay completely clear for five years. Overpromising suggests either inexperience or willingness to say whatever closes the deal.
A good company will also explain what the homeowner can do to extend results: trimming overhanging branches, keeping gutters clear, and considering zinc strips along the ridge.
5. Do you walk on the roof, and how do you handle safety?
Roof cleaning methods vary in how much roof access is required. Some soft-wash systems can be applied entirely from the ground or from ladder positions at the roof edge. Others require some roof walking.
Questions to ask:
- Will anyone need to walk on my roof during the cleaning?
- If so, what footwear and fall protection do they use?
- How do they handle steep or high-pitch roofs?
A company that walks a wet, mossy roof in regular work boots without fall protection is creating a serious risk for their crew and potential liability for you. A company that applies treatment from the ground or roof edge minimizes the most significant safety hazard in the process.
6. Will this void my shingle warranty?
The answer depends entirely on the method used.
Soft washing performed according to manufacturer specifications does not void asphalt shingle warranties. Owens Corning and other major manufacturers specify that low-pressure cleaning with appropriate chemistry is the accepted method for maintaining roof surfaces.
Pressure washing, on the other hand, can void warranties if it is determined to have damaged the shingles. Aggressive manual removal that strips granules can have the same effect.
A reputable roof cleaning company should be familiar with manufacturer guidelines and be confident that their method is compliant. If a company cannot answer this question clearly, they may not know enough about roofing materials to be cleaning them safely.
Our article on low-pressure roof washing for asphalt shingles covers the manufacturer perspective in detail.
7. Can you provide references from homes similar to mine?
This is especially useful for homes with specific conditions: heavy shade, steep pitch, multiple roof levels, tile or metal roofing, or older shingles that may be more fragile.
A company with local experience should be able to point you toward satisfied customers in Hillsboro, Aloha, Beaverton, or nearby communities who had similar conditions. If a company has been cleaning roofs in this area for any length of time, references should be easy to provide.
Checking the company's Google Business Profile for reviews from local homeowners is another way to verify experience with properties like yours.
Bonus: What do you recommend for my property beyond the roof?
This is not a trick question. It reveals whether the company is evaluating your property holistically or just selling one service.
A company that only cleans roofs may not mention that your gutters are contributing to the problem, or that the siding below the roofline is showing the same biological growth, or that the walkway is developing the same moss that the roof has. A full-service exterior cleaning company can assess the entire property and recommend a practical plan that addresses connected issues rather than isolated symptoms.
About Worth It Exterior Cleaning
Worth It Exterior Cleaning is a locally owned company based in Hillsboro, serving homeowners across western Washington County. The team uses manufacturer-approved soft-wash methods for every roof cleaning job and carries full liability and workers' compensation insurance. Every roof cleaning begins with a property assessment and a clear explanation of the method, the products used, and what the homeowner can expect during and after the service.
Service areas include Hillsboro, Tanasbourne, Orenco, Aloha, Beaverton, Forest Grove, Cornelius, and the surrounding west Portland metro communities.
Contact Information
Worth It Exterior Cleaning
9620 Northeast Tanasbourne Drive Ste 300, Hillsboro, OR 97124
Phone: 503-941-0862
Email: info@worthitexterior.com
Request your free quote or give us a call directly.
Frequently Asked Questions
Should I get multiple quotes before hiring a roof cleaner? Getting two or three quotes is reasonable, but compare methods and scope rather than price alone. The cheapest quote often reflects fewer steps, less care, or less insurance coverage. A quote that includes proper pre-treatment, plant protection, and manufacturer-compliant methods is worth more than one that offers only a pressure rinse at a lower price.
How can I tell if a company is using soft wash or pressure washing? Ask directly. A soft-wash system uses a dedicated pump that delivers cleaning solution at very low pressure. A pressure washer, even on a low setting, uses a fundamentally different delivery system. You can also look at the equipment on the truck: a soft-wash rig looks different from a standard pressure washer.
What if a company damages my roof during cleaning? This is why insurance matters. A properly insured company's liability coverage should pay for repairs to any damage caused during their work. Document the condition of your roof before and after cleaning, and report any concerns immediately.
Is the cheapest roof cleaning option always the worst? Not always, but price that is dramatically below competitors usually reflects a difference in method, insurance, or scope. A company cleaning a roof with a quick pressure rinse and no pre-treatment can charge less because the job takes a fraction of the time. The results also last a fraction as long.
Do I need to be home during roof cleaning? Not necessarily, but you should be reachable by phone. Let the crew know about any outdoor spigot locations, gate codes, or specific concerns before they arrive.
