Moss and Black Streaks on Roof!

goddess girl · Joined: 17 Jun 2006 Posts: 29

We recently re-roofed our garage, which had a lot of moss and black streaks on the shingles (presumably from algae). We assumed it was from the constant shade that the garage gets from a nearby tree. While we re-roofed the garage, we trimmed the tree back to prevent this. One year later, and we a little moss has started on one side of the roof. We are aware that it's the constant shade from the tree, but we can't trim it any further.

Does anyone know of how to get rid of this and prevent it for good?

webmaster · Posted: Thu Jun 22, 2006 3:53 am Post subject:

First and foremost, make sure your very careful when working on your roof! Here is a link to a wonderful article by Family Handyman on Roof safety:

http://www.rd.com/content/openContent.do?contentId=18126

Abide by these tips, and when there is moss or algae on the roof you need to be particularly vigilant because wet moss or algae can increase your chances of lost footing...it's very slippery!

With that said, you are right about the constant shade by your tree. This is the most common cause of this problem, that and north facing roof tops. The good news is that there are easy ways of fixing and preventing the problem!

Since it's only been a year since you've had your roof done, that means the moss is not very developed in its root structure. The roots are very shallow, but they can still cause damage to your shingles, especially when left to soak up moister. To get rid of the moss you can use a stiff scrub brush on a pole and scrub your roof with only gentle downward (down the roof) strokes. When you first start doing this, inspect the areas you first clean and make sure your not lifting any of the roofing granules with the moss. Loss of these granules compromises the protective integrity of the shingle. Don't worry about getting every little piece of moss.

Don't worry about the algae at this point. It's immediate remove is not necessary, because algae doesn't hurt your shingles,it just hurt the appearance.

Step #2 (this step kills the remaining moss and algae)
Some recommend using a water/chlorine bleach solution to spray on the roof. This works well. However, if you have surrounding plants you need to take steps to protect them, because the bleach can certainly kill valuable foliage on top of your roof moss! To protect your plants you can use an oxygen bleach solution, such as Oxyclean. If you use either of these steps make sure your roof is shaded at the time (you probably won't have this problem), so that the bleach solution has time to soak into the moss and algae. Another alternative to chlorine bleach is powered laundry detergent with bleach. You can sprinkle it on at any time, and either wait for it to rain, or just spray it lightly to get it working. As the detergent dissolves, it starts working on your moss/alge enemies. Laundry detergents are really good at this because they contain enzymes that accelerate the cleaning (or killing). I particularly like this method because you just spread it, and forget it!

The next step is to prevent the moss and algae from coming back. You can do this by re-roofing your house with an antifungal shingle. These shingles typically have grains of copper embedded in them, and copper molecules destroy algae and moss. Though re-roofing a roof that is only a year old is not an option. In stead you can use strips of zinc (good) or copper (better), and install them toward the ridge of your roof. As it rains, small copper or zinc particles get washed down your roof, and prevent resurgence of spores. There are a couple techniques to installing these strips, let me know if you go this route, and I'll give you some pointers.

Let me know if you have any other questions! Cool

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