TL;DR
- No high pressure on roofs — it strips granules, loosens shingles, forces water underneath, and can void warranties.
- Soft washing uses low-pressure specialized solutions to kill algae, moss, and black streaks at the source (safer and longer-lasting).
- Cleaning solution is safe for plants and animals when properly diluted and applied by professionals.
- Landscaping protection includes pre-wetting plants, correct dilution, controlled application, and rinsing as needed.
- Fully insured companies protect you from liability if something goes wrong (always ask for proof of insurance).
- Results make the roof look significantly cleaner and brighter, but won’t restore a worn or aged roof to brand-new condition.
- Rinsing is often left to rain; low-pressure rinsing is used only when needed — never high pressure.
If you’re thinking about getting your roof cleaned, you probably have a list of questions running through your mind. Roofs are a big investment, and the last thing anyone wants is damaged roofs, damaged landscaping, or a result that doesn’t match the promise.
We get these same questions every week from homeowners. So instead of dancing around them, we’re going to answer them directly—just like we would if you called us today.
Do You Use Pressure on Roofs?
No. We do not use high pressure on roofs.
Pressure washing (the kind of force that works great on concrete or driveways) is one of the fastest ways to damage asphalt shingles. High-pressure water can:
- Strip away the protective granules that shield the shingles from UV rays
- Loosen or lift shingle tabs
- Force water underneath the shingles, which can lead to leaks later
- Shorten the overall life of the roof
Many roofing manufacturers specifically warn against pressure washing for these reasons. Using high pressure can even risk voiding a roof warranty.
That’s why we rely on a completely different approach.
What Is Soft Washing and How Does It Work?
Soft washing is a low-pressure cleaning method that uses specialized solutions to kill the organisms causing the black streaks, algae, moss, and mildew on your roof.
Here’s the basic process:
- We apply a carefully mixed cleaning solution at very low pressure (similar to a garden hose).
- The solution does the work—breaking down and neutralizing the algae, mold, and organic growth.
- Over the next hours and days, the dead growth rinses away with normal rain or is gently rinsed if needed.
- The result is a cleaner roof without the mechanical force that damages shingles.
Soft washing treats the cause of the staining instead of just blasting the surface. That’s why results tend to last longer than pressure washing alone.
Is the Cleaning Solution Harmful to Plants & Animals?
When applied correctly by trained professionals, the solution is not harmful to plants, pets, or wildlife.
The active ingredient is typically a diluted form of sodium hypochlorite (the same compound found in household bleach, but mixed at a controlled strength for roofs). At the proper dilution, it effectively kills organic growth on the roof while remaining manageable around landscaping.
The key is how it’s used. Concentration, application technique, and plant protection all matter. That’s why DIY roof cleaning often causes more problems than it solves—people either use too strong a mix or fail to protect the surrounding plants.
How Is Landscaping Protected with Pre-Wetting and Diluting?
We take plant protection seriously because we gardens and the beauty they bring to homes.
Our standard process includes:
- Pre-wetting all nearby plants, shrubs, and grass with clean water before any solution is applied. Saturated plants are far more resistant to any incidental runoff.
- Using the correct dilution for the level of growth on the roof (we never apply full-strength solution).
- Controlling overspray and managing runoff so solution doesn’t pool on landscaping.
- Rinsing plants again after the application when needed.
These steps dramatically reduce risk. Professional soft washing crews who follow these practices routinely clean roofs without harming surrounding plants or grass.
Why Hiring a Fully Insured Cleaning Company Matters
Roof cleaning involves ladders, heights, chemicals, and working on one of the most important parts of your home. Accidents can happen.
If a company is not properly insured and something goes wrong—property damage, an injured worker, or damage to a neighboring home—you could be left holding the bill. Homeowners insurance may not cover claims caused by an uninsured contractor.
A fully insured company carries general liability coverage and workers’ compensation. This protects both you and the crew. It's a simple shield that serious companies always have.
Will Your Roof Look Brand New After Cleaning?
It will look significantly cleaner and brighter—often dramatically so—but “brand new” depends on the condition of the roof itself.
Soft washing is excellent at removing black algae streaks, moss, and organic staining. Most roofs look much fresher the same day or within a few days as the dead growth continues to rinse away.
However, cleaning cannot restore granules that have already worn off, reverse years of UV aging, or fix physical damage. An older roof will look cleaner, but it won’t magically regain the appearance of a brand-new install. Moss can grow and in most projects it is left to die and slough with wind and weather (saving the risk of climbing the roof as well as the wear of scrubbing the shingles). The goal is a well-maintained roof that looks its best for its age, not a cosmetic miracle.
Do Roofs Need to Be Rinsed Afterwards?
It depends on the situation.
In many cases, especially with lighter growth, we allow the solution to dwell and let normal rainfall finish the rinsing process. This is often gentler and more effective for thorough results.
For heavier growth or when faster visual results are preferred, a low-pressure rinse may be used. The important point is that we never use high pressure. Any rinsing is done carefully and at low force so it doesn’t damage the shingles.
Your specific roof condition and local weather help determine the best approach. We’ll walk you through what to expect before we start.
Roof cleaning doesn’t have to be mysterious or risky. When done the right way—with soft washing, proper plant protection, the correct solution strength, and a fully insured crew—it protects your investment and restores curb appeal without the downsides of high-pressure methods.
If you have more questions about your specific roof, we’re happy to answer them. The best decisions come from clear information, not guesswork.
About The Author
Andrew Cox, Founder of Cox Exterior Cleaning Co.
Hi! I'm Andrew Cox, a former physical therapist, who got tired of bureaucracy and selling chances, and started Cox Exterior Cleaning Co. to serve Knoxville in a new way - making things beautiful again. I wrote this article so that any of those burning roof wash questions might be answered, because...who likes to hold onto burning questions?
