Roof cleaning - tips?

what's on your roof that needs cleaning off?

Get up there and sweep, wash down and hose off with a power hose. (or just use the power hose).

Here is an article that might help - https://www.familyhandyman.com/roof/roof-repair/how-to-clean-roof-stains/view-all/

Use Wet and forget safe for all surfaces

Have a friend who is a chimney sweep. He gave me some advice for killing moss that grows on a roof. Buy a big box of cheap dishwasher detergent. Before a good rain (one that lasts several days) climb up onto the roof and sprinkle that around especially at the peak. The rain will wash it down and the moss will die. We tried it this last fall and it does work!

The black mold-like stains and streaks that appear on roofs, particularly light-colored asphalt shingles, is actually a blue-green algae (Gloeocapsa magma). Commonly found in climates with warm, humid summers, it does no damage to the roofing, but it certainly does looks bad.

The less expensive solution is to spray wash the roof with a 50 percent mix of water and bleach to get rid of the algae. (No pressure washers, please. They're likely to damage the shingles.) Just be sure to wet your foundation plantings first, and rinse everything in clean water when you're done. Plants don't like bleach, and wetting them with plain water first protects them. You can also cover them with tarps or plastic sheeting, which will protect the soil around your plants as well. Make sure that you create a wide radius around your home to be safe.

Allow the solution to soak into the shingles for at least 15 minutes. If they are severely molded, you may want to give it a little longer. Next, rinse the shingles thoroughly with a garden hose at low pressure. Start from the top shingle and rinse downward to prevent water seepage.

To keep the algae from coming back, insert 6-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles.

You can probably see this same principle working on roofs in your neighborhood. Look for chimneys with copper flashing; the areas directly below the flashing will be free of any algae stains.

The strips also work on roofs suffering from moss buildup. Just scrub it off first with a brush, then bleach as above.

We use Wet it and Forget it spray.

Why not just pressure wash the roof? This seems to be the easiest option.

Agreed. I think pressure washing should have been brought up in this thread. It is a perfectly valid option in this situation.

Agreed. I think pressure washing should have been brought up in this thread. It is a perfectly valid option in this situation. If you cannot afford pressure washing equipment or the necessary chemistry or you don't see any use in them beyond cleaning the roof simply order commercial exterior cleaning services similar to the one I embedded in this post. This might not help the original poster since the thread is pretty old. However, this might help someone browsing old threads, looking for solutions to similar problems.