A house I purchased had huge trees over half the house and parts of the roof hardly saw sunshine for a long time. I since cut the trees down so the roof now gets some sun (Indirect since its on the back of the house). There are some dark stains and old blue/dried moss or algae. What's the best method of giving the roof a gentle cleaning? Its an older shingle roof, I would say I will probably replace it in another 5-7 years or so. So just something to help clean it up a bit, without ruining it.

I've used Wet&Forget on my last house and I'm still not so sure how well it worked overall. That product works slow over time. I can get up there and use this, but I wanted to ask what else others are using to give the roof a cleaning without being too rough.

I've seen all sorts of recommendations from diluting bleach, to products, to sprinkling zinc and other methods. I know a copper/zinc strip installed at the top will help keep things at bay, but since the roof now isn't covered in trees I don't think I'll have much of a problem after I get the old stuff off.

No I would never power wash a roof so that's out of the question. I will go up with the hose and spray on whatever needs to go on, or use a light brush in any stubborn areas.

The front of the house has a hard pitch but it looks great up there, no issues at all. Its only the back side, and I can easily get up there and walk around so I can do whatever I need up with ease.

Hit me with your best tips to give this roof a cleaning.

  • 1
    Wet & Forget is still the best bet. Even talked my condo association into using it on our tile roofs. Works great, but you have to be patient.
    – RMDman
    Apr 12, 2023 at 22:13
  • @RMDman Thanks for the extra info. I'm going to go Wet & Forget then unless someone shares something else worthy. I will say with patience it has done good for me on other homes in the past. I already have a bottle ready to go so its on my To-Do list soon.
    – RocketManZ
    Apr 13, 2023 at 15:20

1 Answer 1


I've tried the zinc strips at the peak and they just aren't effective....not enough surface area. They need rain water and even though I'm in western Washington state, which gets a lot of rain, the strips didn't seem to make a difference.

In my case I used a local company to power wash (not pressure wash) with their specialized bleach based solution. It's a gentle wash. They scraped off the worst of the moss and then sprayed on the solution...again, this was not a pressure wash. It took a few weeks for it to fully treat the roof, but it turned out great. Two years later, the roof still look brand new.

  • Thanks for the details. Since this roof is on the older side, I will probably use the Wet & Forget, and just let it do its thing over the long haul of time. This is on the backside of the house on a dormer with average pitch, so its only me that's looking up there and thinking about it. Good to know there are people offering a service like this though, I'll keep it in mind for the future.
    – RocketManZ
    Apr 13, 2023 at 15:21

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