My roof looks like it's in good shape but there are some dark stains (maybe from trees) that really make the roof look bad. Can the shingles be cleaned?

 

I have cleaned shingles before [only for realtors] with detergent and a pressure washer BUT I DON'T RECOMEND IT!!!
While the end result will be a nice clean roof it puts a lot of wear on the roof and can drastically shorten its life span.

 

I'd run this question past a supplier of shingles. *I* sure wouldn't want to be responsible for giving some bad advice that results in a rapid deterioration of your shingles! I definitely wouldn't use any unnatural pressure cleaning, as that could blast the granules off. But...we know that roofs see hard pouring rain, so, maybe *some* type of cleaner with a gentle rinse afterwards could work. But do not use any solvent (water based or otherwise) that disolves grease!! as this could disolve asphalt! I have already put a degreaser on a top coat ashalted driveway and washed away that top coat! But I'm thinking *maybe* bleach might have some positive effect.

*But*...suppose that were to work. What if it worked *toooooo* good? (Or any recommended cleaner for that matter?) It could make the roof area actually look unnatural and *worse* then, if you then didn't clean then the entire 1/2 (side) of the roof!

Just a thought.

 

Here's a post from an earlier thread.
It can apply here.
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As mentioned earlier, pressure washing will knock the granules off the shingle which will expose the asphalt underneath. The granules serve only one function (other than make your roof colorful)....they protect the asphalt, which is the shingle's waterproofing, from the sun's UV rays. Without granules, the exposed asphalt would deteriorate much faster and drastically shorten the life of the shingle.

Mold/algae/fungus is very common along the gulf coast and other humid areas.

The most popular theory is this:
Mold typically grows on the north and west sides first because the sun rises in the southeast most of the time (since we live in the northern hemisphere). Therefore, the north and west sides of a roof tend to hold more moisture since the morning dew burns off slower.

You can use a very low pressure wash with a bleach solution to wash off the mold/algae.
The most common "home remedy" is 1/3 water, 1/3 bleach, and 1/3 TriSodium Phosphate (TSP). The more bleach, the better, however, your plants on the ground do not like bleach....so beware of the runoff.

Basically, you could spray your solution on the area, let it sit for 15 minutes or so, then wash it off. Darker areas may need to be sprayed more than once.

 

I contacted a shingle manufacturer when doing my roof and their recommendation was 1 cup TSP, 1 gal. bleach, and 4 gal. of water. I am going to be doing mine this weekend. Good luck with yours. I have pressure washer that I am going to use to apply my cleaner and it has a ratio mix of 1 gal. chemical to 7 gal. of water. So I will use that mix ratio which is a little more diluted than they shingle company calls for but that should be a good thing. I will use a hose to rinse the roof and I don't want to use a pressure washer's high pressure on my shingles for rinse.