Should I ever power wash my roof? If not, what’s the best way to clean your roof?

Recognize that moss, mildew and algae are all living creatures that have taken up residence on your roof. Trying to remove them in one fell swoop can often be, not just difficult, but sometimes impossible without ruining the roof. If you come at this with the strategy of I want to reduce the amount of mold, mildew and algae on my roof by half over the next 3 or 4 months and then half again after the next 3 or 4 months after that, it’s very easy to do.

Assuming that you’re physically capable and it’s safe for you to walk on your roof, see our safety section; that’s really important. We don’t want to tell people to do stuff that we haven’t advised them on the safety side of it. Assuming that you have done those things, that you are capable and that you are safe, one of the easiest things that you can do is add detergents and over the counter moss, mold and mildew treatments to your roof.

Essentially the way that this works is you pour them along your ridge line and you let the natural weatherization of the roof, the next rainstorm gets what you placed on the ridge line wet and then starts carrying that, those chemicals, down the roof, coating the whole roof. There will be, unless you have a real deluge, there’ll be some chemicals remaining on the ridge line that with subsequent rainstorms will continue to kill the moss, mold and algae that are growing. This goes a long way in relieving the problem.

What it doesn’t solve is that dead mildew and dead moss still can leave a residue even if they’re no longer living. That’s where you have to bring in a company with specialized power washers that are low pressure, high volume that is pressure below 2500 psi and volumes beyond 5 gallons per minute to wash those roofs. Even then it is not guaranteed that it will not come clean. Moss, mold and mildew, once it’s taken hold, can be very difficult to remove if not impossible.

That’s why we always recommend using shingles with moss, mold and algae inhibitor built into them. This is done by taking the granules that we talked about and coating them with a copper or other leaching metal that leaches into the water that comes off of the roof. This then is absorbed by the moss, mold, mildew, algae and causes it to either be heavily retarded in its growth or kills it altogether.

If you’re in a neighborhood that has moss, mildew, mold growth on the roof and you want to see this in action, look at the vent pipes or metal ventilation on the roofs and look below those areas. You’ll generally find that below those areas, there’s less mold, mildew and algae growth. That’s because the coating that’s on the metal, especially galvanized metal, as it leaches out with water touching it, actually strongly inhibits the growth of mold, moss, mildew and algae. This is proof and demonstrates what the shingle companies are now impregnating into their more expensive or upgraded shingle lines.

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