By Paul Bianchina
Q: Someone once suggested that I could sprinkle Tide on my fiberglass roof shingles to control moss. I've been doing that for several years with good results. Is there any evidence that this will do long-term damage to the roof, such as loosening the granules? - Don D.
A: Since bleach is an oxidizer, it is effective at killing mildew, moss and mold. Therefore the Tide you've been using will certainly work against the moss, as will any other laundry detergent or other cleaner that contains bleach.
I am not aware of any detrimental effects to the roofing from the detergent itself, other than the possibility of discoloring the shingles. However, if you are using a heavy spray or trying to brush the shingles with a push broom or other brush, you can dislodge a lot of the granules and cause the shingles to fail prematurely.
A couple of other things to consider: Depending on the manufacturer, you may be voiding their warranty by washing or otherwise "treating" the shingles, so you might want to check with them as well. Also, large quantities of detergent can harm landscaping and possibly be detrimental to wildlife, and some communities also have regulations against soap being directed into storm drains, sewers, or other public areas.
Wherever possible, take whatever action you can to reduce the causes of the mildew and moss. Keep trees trimmed back, keep gutters clear and flowing properly, and keep leaves and pine needles from building up on the roof.
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