12/6/2013 10:47:00 AM Cleaning moss, algae off roof can cause irreparable damage: Better to remove whatever is causing shady, moist conditions
Sandy Griffis Yavapai County Contractor’s Association
Q: We have started to notice black stains on our roof. Do you know what might be happening? Do we have a worry?-Michael and Patricia, Groom Creek
A: More than likely, your roof is growing moss and/or algae. This is not a serious issue; it just looks unsightly. Moss/algae forms on shingles that have a lot of shade and moisture and is very prevalent in areas heavily shaded by trees, which produce high levels of humidity and moisture. Areas in the Pacific Northwest, Southeastern and the Mid-Atlantic states have extremely high moss and algae issues. The algae spread via airborne spores where moss actually grows in place and is produced due to lack of sunlight, and moisture.
We talked with Phillip of Bradshaw Mountain Roofing and he recommended that you not have the shingles cleaned or power washed. This process would remove the granules. Granules are there to protect the roof against the sun's UV rays, and once they are gone, shingles become very brittle. Shingles that have little or no granule protection are usually old and in need of replacement.
Shingle manufactures make a product that is algae-resistant; however, according to Phillip, these shingles are more commonly used in the Northeast. They can be special-ordered and are more expensive than standard shingles. They look like normal shingles, but are made with copper granules mixed in with standard roof granules. There is a mix of approximately 10 percent of the copper granules with standard granules.
Moss/algae growth is generally harmless, and there are not any really great options for preventing this moss/algae growth with the exception of the algae-resistant shingles.
To stop this growth you should remove the conditions that are more than likely causing the moss/algae to grow. If you have a shady climate, take away the shade and moisture. More than likely this will involve removing trees and opening up the tree canopies, allowing sun to penetrate the roof. Since our weather environment is not often overcast and cloudy, and you probably have a high level of shade from trees, allowing more sunlight through will stop growth of the algae and/or moss.
Without a roof inspection, we do not know if you have algae or moss growing on the roof. Moss is a more serious concern because if it is allowed to continue to grow on the shingles, the moss can eventually raise the shingles, allowing water to infiltrate and create a roof leak. Moss will trap debris on the roof, which can create a building up of material, which can create leaks and rotting of roof material, breaking down of the shingles.
If the black streaks are algae, then zinc strips that have a fungicide in them can be placed on the roof. When it rains, the fungicide is released and will kill the algae.
As we have mentioned in the past, you should have your roof inspected every 3-5 years. Here are some helpful hints for roof longevity:
If your roof is missing shingles, you might possibly have a critter on your roof that has loosened or broken them. Another reason for missing shingles is damage to the sealant strip. If your shingles are cupping and looking wavy, there is probably an issue with attic ventilation. Lack of attic ventilation is not the root cause for cupping shingles, but can contribute to it.
If your shingles are cracking, then the granules have probably worn off. You'll want to look into having the roof replaced.
If you have a roof leak during the winter with thawing and freezing temperatures, then you have ice dams that are building up. This is a huge concern in our area and will cause havoc. Ice dams are caused by freeze and thaw cycles that allow ice to build up on the roof and will not allow the melting snow to drain off into the gutter system. The ice dams cause the back-up water to flow under the shingles and leak inside your home.
Yavapai County Contractors Association (YCCA) is a professional association representing licensed, bonded and insured contractors, suppliers, distributors and business entities. Call YCCA for information on hiring a contractor at 778-0040. Submit questions to firstname.lastname@example.org or through www.ycca.org.