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Busting roof cleaning myths in Renton, Washington

Busting the roof cleaning myth in Renton, Washington

Roofers Renton, WA
Say no to damaged roofs!

To pressure wash, or not to pressure wash, that is the question. Everyone has their own home remedy for just about everything, roof cleaning is no exception. The biggest debate and misconception for roof cleaning is whether or not you should use a pressure washer on roofing shingles.

The answer to the question is really simple, pressure washing your roof voids the manufacturer warranty. The pressurized stream of water not only effectively removes moss and algae, it also removes the granules from your shingles! The granules are a very important waterproofing aspect of the shingle. They are embedded into hot asphalt as the outer waterproofing layer. Damaging the shingle by stripping off the granules not only voids the warranty, it can also remove years from the life of the shingle and cause roof leaks.

Roofers Renton, WA
This damage was done while pressure washing this roof!

Now the questions remains what is the proper way to clean a roof. The best place to go is right to the top. I want to hear from someone that doesn’t have a financial stake in this questions. The asphalt roofing manufacturers association has released a technical bulletin addressing the issue. The agreed method for proper roof cleaning is as follows:

“Algae discolorations are difficult to remove from roofing surfaces, but may be lightened by applying a solutionof chlorine bleach, trisodium phosphate, and water. Solutions for these ingredients may vary between shingle manufacturers and depend on the amount of discoloration. Solutions range from one cup TSP, one gallon bleach andfive gallons of water, to one cup TSP and 2.5 gallons each of bleach and water.

 First, gently disperse this solution on the roofing surface. Use normal precautions for handling bleach. Be sure to applyit carefully to avoid damage to other parts of the building and its surrounding landscape. Avoid scrubbing the surface,as this friction may loosen and remove granules. If possible, always work from a ladder and/or walkboards to avoiddirect contact with the roof surface. Observe all possible safety precautions when working on or near the roof. Finally,rinse the solution from the roof by gently spraying the surface with water. Be warned that this solution application and rinse process will make the roof surface slippery and potentially hazardous to walk on during treatment.

 The effectiveness of such cleaning techniques are only temporary, and discoloration will likely recur. However, several types of algae resistant roofing products have been developed, and are now commercially available. These asphalt roofing products are specifically designed to inhibit algae growth for extended periods of time.


High pressure washing systems for algae removal should not be used.”

-Asphalt Roofing Manufacturers Association

Well, I think that pretty much sums it up. A chlorine bleach solution is the manufacturer recommended way of roofing cleaning. So next time a slick salesmen comes to your house and wants to get up on your roof with a pressure washer, you know what to do.

Thank you for reading the Chase Construction North West, Inc roof life blog. We are 1 of 15 GAF Master Elite roofing contractors in the state of Washington. We have proudly served as a premium roofing contractor in Renton, Washington for over 11 years.

If you would like a free quote or roofing consultation call us at (253) 544-3651 or fill out our quick estimate form.


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