Is Pressure Washing Safe for Your Roof? Why We Soft Wash Instead
No. Not on an asphalt shingle roof. Here is what high pressure actually does up there, and what should be used instead.
What protects a shingle
An asphalt shingle is a mat saturated in asphalt and covered in ceramic coated granules. Those granules are not decoration. They are the only thing shielding the asphalt from ultraviolet light, and they are what determines how long the roof lasts.
Strip them and the asphalt underneath starts ageing immediately. That is the entire risk in one sentence.
What high pressure does
A pressure washer removes roof algae quickly, and it removes granules just as quickly. From the ground the roof may look cleaner. In the gutters afterwards you will find a gritty black sediment, and that sediment is your roof.
It can also drive water up under the shingle course, which puts moisture in the roof deck rather than on it. That is a considerably more expensive problem than the staining you started with.
The warranty problem
Shingle manufacturers do not list pressure washing as an approved cleaning method, and granule loss caused by it is generally excluded from limited warranty coverage. So the worst case is not just a shortened roof life, it is a shortened roof life with no recourse.
Check your specific warranty if you want the detail. The safe path is simply not to let anyone put high pressure on it.
What we do instead
soft washing does the work with chemistry rather than force. A cleaning solution goes on at roughly garden hose pressure, gets time to kill the algae at the root, and is rinsed gently. Granules stay where they belong.
Because it kills the organism rather than knocking off the visible layer, the results also last far longer than a pressure clean would. This is not a compromise for the sake of safety. It is the better clean.
If a contractor offers to power wash your shingle roof, that is your signal to call someone else. Free quotes at (904) 506-7656.
What a proper roof clean includes
- Pre wetting and protecting landscaping and surrounding surfaces
- A solution mixed for your roof material rather than one universal mix
- Enough dwell time for it to actually work before rinsing
- A low pressure rinse that leaves granules undisturbed
- Attention to gutters and fascia, which almost always need it too
- Minimal foot traffic on the roof itself
Tile and metal
Concrete and clay tile crack under both foot traffic and pressure, and they are common around St. Augustine and Ponte Vedra. Metal roofs carry coatings that the wrong chemical dulls permanently. Neither should be treated like asphalt. A contractor who has one approach for every roof will eventually damage one.
Questions worth asking
- What pressure will you use on my roof?
- What is in the solution and how do you protect my plants?
- Will anyone walk on the roof, and how do you limit that?
- Are you insured, and can you send the certificate?
We clean roofs across St. Johns, Fleming Island, Mandarin and Orange Park.
- Granules are the only UV protection an asphalt shingle has.
- Pressure removes algae and granules together, and the gutters show the evidence.
- Manufacturers do not approve pressure washing, so damage is usually not covered.
- Soft washing is both the safe method and the longer lasting one.
Frequently asked questions
Is pressure washing ever safe on a roof?
Not on asphalt shingles. Tile and metal have their own constraints too. Low pressure with the correct solution is the right approach across the board.
How can I tell if my roof was pressure washed?
Check the gutters and the ground below the downspouts for a gritty black sediment. That is granule loss.
Does soft washing really remove the black streaks?
Yes, and because it kills the algae at the root rather than knocking off the surface, it stays clear far longer.
How long does it last?
Commonly several years on a Northeast Florida roof. Heavy shade and overhanging branches shorten it.
Will you need to walk on my roof?
We minimise it. Soft washing is largely done from ladders and the ground with specialised equipment, which is safer for the roof and for the crew.
Free quotes across St. Johns, Clay and Duval counties. Call (904) 506-7656 or request a quote online.