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Roof Moss Removal from Composite Roofs

Composite roofs are very popular in the Pacific Northwest. They are basicly a sheet of tar paper with granules stuck on them. The granules protect the tar shingle. The tar shingle protects the thinner tar paper underneath. The thin tar paper protects the plywood and so on. The key to making your roof last longer is keeping the granules on. You can make the granules stay on longer by: keeping the roof clean, applying a moss/mildew prevention so that moss and mildew don't get started.

Zinc-killed moss on composite roof
Photo by Brad Lewis

If you already have moss on your roof, it should be killed first. If you roof is very steep and you don't mind looking at the dead moss, you can let it weather off the roof. The gravity and rain will work to your advantage. Moss prevention should be applied to the roof every year or two to make sure that more moss does not grow on the dead moss.

If you don't have a steep roof or if you don't like the looks of the dead moss, you can have it removed. There are three main ways of removing the moss from your roof. It may be swept, brushed or pressure washed. If your roof is easy to walk on and the dead moss is bulky, it may be swept off to remove the majority of the moss. Smaller pieces of moss will remain. No matter the steepness or pitch of your roof, the dead moss may be brushed off. The advantages of brushing is that it works on any pitch, removes almost all of the visible moss, and it looks great quickly. Also, only the areas of the roof that have moss on them are brushed, the rest is not touched. Brushing removes fewer granules than pressure washing and helps your roof last longer.

Same shingles that have been handbrushed free from moss
Photo by Brad Lewis

The third method of moss removal is pressure washing. The reason I don't offer this roof pressure washing is because: insurance is so high because of water damage, it causes some roofs to leak immediately and water stain ceilings and carpets, it lifts the composite shingle to shingle tar seal and it can cause long term water damage that leads to roof rot under the shingles. I see many disadvantages in pressure washing a composite roof. Typically from contractors I've heard that the composite shingles will lose 3-5 years of life from pressure washing.

Bleach solution that is too strong will ruin composition shingles
Photo by Brad Lewis

Please choose your roof type for more specific helpful information:
   Moss removal from composite/3 Tab shingles
   Moss removal from concrete flat tile roofs