Roofing Tips: Removing Algae Stains Part II

Do you have unsightly algae stains on your roof?  Get informed before you act! Jared talks with homeowners about fungus, algae and manufacturers’ warranties.

Jared: We’re talking with Lynn; how can we help you today?

Lynn: Hi Jared. Well, our home is about eight years old. The roof on the house looks to be in good shape, but there are black streaks on it. Homes left and right of us that were built before ours don't have this. I was told this is a sort of mold. Is there anything we can do about that, or is it just something we have to live with?

Jared: Lynn, that discoloration is most likely fungus, algae or some sort of mold. Most shingles made today are fungus and algae resistant. What they do is use a ceramic coated copper granule - it used to be zinc – in the shingle. What happens is the water gets on that copper, the copper leeches out, and that kills the fungus and algae. That is how it is fungus and algae resistant, but there is no such thing as fungus and algae proof. If it is outside in a humid environment, then the odds of it getting some sort of discoloration are pretty good.  It is possible that your roof is not even fungus and algae resistant but your neighbors' are. That would be one reason for it. Or it is possible that while in the first five years or so, the algae resistance is more prevalent and works better; but with age, the granules fall off.

Many shingle manufacturers of shingles, though, have fungus and algae resistant portions to their warranties - some ten, fifteen or twenty years. It's possible that the manufacturer of that shingle would actually cover the cost of what it would take to replace it. Do you know what manufacturer of shingles you have?

Lynn: It’s hard to say. I believe it was Timberline; my husband was looking for the paperwork. I have heard about the copper granules and copper stripping at the top, but cosmetically right now, there's nothing we can do about it except to replace the roof?

Jared: Oh no, you don't have to live with it. If it’s a discoloration from fungus and algae, it's not necessarily going to affect the useful life of the roof; you can ether clean it yourself or have it cleaned. If you're going to do it yourself, then the Asphalt Roofing Manufacturers' Association recommends trisodium phosphate, TSP, along with a pool-grade chlorine. Then there's a material called Wet and Forget where you spray it up there, and you just kind of let it sit - you don't rinse it off or anything - and that will clean it. If you're going to hire somebody, there's all sorts of great roof cleaning companies.

Lynn: Yeah, the fellow that pressure washes our house said that he could do it, but I didn't want anybody going up on that roof until we talked to a professional. I think he was just going to use chlorine on it.

Jared: Chlorine is okay, but don't let him pressure wash it. Understand that the fungus and algae will come off, but it'll take the granules off at the same time. You don't want to pressure wash it; you definitely want to use some sort of chemical cleaning system. Go to the manufacturer's website - if it is Timberline, that manufacturer's name is GAF. They actually have suggestions on their website on how to clean their products.

Lynn: Would it just be something you would spray on the roof and then just let it sit and do its job. You wouldn't rinse it off or anything like that? 

Jared: If you're using chlorine, you would want to rinse it off. If you don't have gutters, you've got to be really careful because the chlorine will not only kill that living plant on the roof called fungus and algae, it'll kill the rest of the living plants around the of the outside of your house.

Lynn: We do have a gutter system around the whole house. I could check with the manufacturer first to see what to do. It's such a pretty house, and it's so disturbing to look up there and see this. I'm not quite sure, maybe because it's a darker roof. The house is north south facing, so I don't know if that has anything to do with it.

Jared: Eventually, every roof will get fungus and algae on it. I'm not concerned about it, but if I remember correctly, I'm pretty sure GAF had a ten-year fungus and algae resistant warranty at that time, so you're within the warranty period. You may want to contact GAF, and they actually may even pay to have it cleaned or send somebody out.

Lynn: Oh, that's wonderful news. Okay, thank you so much. You've answered all of my questions.

Jared: Sounds good, Lynn. We appreciate your call.

For more information on roof cleaning, visit the ARMA website or watch the ARMA Guide to Algae Discoloration videoListen Saturday mornings to "In the House". Get more Home Tips and show info at the In the House website. For a free inspection and estimate on your next Home Improvement Project, visit Universal Roof & Contracting or call now. Orlando: 407-295-7403 Jacksonville: 904-647-3907.

Go back