Ask The Builder vs The Shingle Manufacturers

Midwestpro

I copy and pasted this from a roof cleaning link on askthebuilder.com by Tim Carter.

Wind broadcasts spores, they can drop from trees and birds can deliver them to a roof surface. The abundant water you get from periodic rainfall fuels the growth of the moss, lichens and algae. Since the north, northwest and west sections of your roof stay in the shade during the early part of each day, the dew that develops on the roof at night does not evaporate quickly. This morning moisture quenches the thirst of the mini-vegetable garden up on your roof. The other sections of your roof dry too quickly and the moss, lichens and algae die of thirst.

You can use a pressure washer to clean moss, lichens and algae from asphalt shingle roofs. But, you must be careful! I have also heard urban legends about pressure washers causing permanent damage to asphalt roof shingles. I know for a fact that pressure washers can damage concrete, so it would seem likely they might harm shingles. But since I know how to quickly and easily replace one or more roof shingles, I decided to do a test of my own. What's more, I felt my roof would be a good one to test since it is now twenty-years old, and at the end of its useful life. I also decided to test some new shingles to see if the pressure washer blasted away many or all of the colored granules.

The roof-shingle-cleaning test started with a gasoline-powered pressure washer that develops 2,500 pounds per square inch of pressure while delivering 2.4 gallons of water per minute. I equipped the pressure washer spray wand with a 25-degree tip. This tip is used for general-purpose cleaning.

The results of the test were astonishing. I was able to remove all of the moss, lichens, algae and twenty years of dirt with the pressure washer. No damage was done to the asphalt shingles whatsoever.

I started with the spray wand tip about twelve inches from the surface of the shingles and aimed the wand down the roof. I didn't get any noticeable cleaning results at this distance. But once I slowly lowered the wand to within 6 inches of the shingles, the organic growth started to disappear. My suggestion to you is to carefully clean just one shingle and stop working. Inspect the shingle for damage.

Walk to another part of your roof where the shingles look great to see if the clean shingle looks just like the freshly-cleaned shingle. Rest assured you will readily spot damage. If you see small or large patches of solid black or fiberglass mesh, you are ruining your roof.

You can use a regular garden hose and a scrub brush to clean your roof. It will be an enormous amount of work to say the least. Always point the garden hose or pressure washer wand down the roof. Never point it up the roof, as water can be driven up under the shingles creating massive leaks inside your home.

Wow Tim that is amazing considering that the major shingle manufacturers recommend a low pressure chemical application and WARN against the use of a pressure washer on asphalt shingles, enough said!

Who are you going to believe; some inexperienced journalist trying to make a buck or the people that actually produce asphalt shingles? Doesn't seem like much of a match to me, sorry Tim!