LESLIE: Doug in Rhode Island’s got moldy shingles. Tell us what’s going on.
DOUG: Yeah, I have … I enjoy your show and I have a question. I have – I believe I would say it’s mold – growing on my asphalt shingles. They’re basically green spots, various sizes. And I’m not sure if I should brush these off or if there’s a treatment for that. And if I do brush them, would that damage the shingle?
TOM: That’s actually a very common condition. Typically, it happens more on very shady roofs and when you don’t have a lot of sunlight getting to it, then the moss has a chance to grow. Because that’s what it is; it’s moss. There is a product out called Jomax – J-o-m-a-x – that’s very good for getting rid of that. It’s available at home improvement centers and paint stores. And you mix that up; you spray it on the moss; you let it sit for a little while; and then you scrub it off. You can do that with a stiff broom or you can do it with a pressure washer.
As for your question about will this damage the shingles – well, first of all, the moss will not. This is really just a cosmetic issue. But if you put too much pressure – too much scrubbing pressure or too much of a pressure washer – you could, in fact, damage the shingles.
Now, there is another way to prevent this from happening after you get it clean. First of all, of course, get as much sunlight on that part of the roof as you can. So if you can cut back some of the tree limbs so there’s more exposure, do that. The second thing you can do – a bit of a trick of the trade, Doug – is to add a copper ridge vent at the peak of the roof.
LESLIE: Or even a nickel ridge vent.
TOM: Or a nickel ridge vent. Because either copper or nickel – as the rain strikes it, it will release some metals into the water and that acts as a mildicide and actually cleans the roof as the water runs down it.
So, nothing structurally to be concerned about; really cosmetic. That’s how you get it cleaned off and that’s how you stop it from growing back.
LESLIE: And remember, Doug, be real cautious when you’re working up on your roof. You want to make sure that you feel comfortable up there before you go up and do any sort of home improvement.
TOM: That’s right because it’s going to be very slippery when you use those chemicals.