Moss will shorten life of homeowner's roof
homeowner's By SAMANTHA MAZZOTTA Q: I have a huge butternut

Q: I have a huge butternut tree that completely blocks out all sun on the north side of my roof. I assume that is what caused all the moss that grows in between the shingles. First, will the moss hurt the roof, and if so, how do I get rid of it? - Carol S.

A: Moss grows where there is little direct sunlight, and it can do extensive damage to a roof if not kept under control. On some types of roofs, such as those with wood shingles or heavy tiles, moss takes hold in the deeper cracks and crevices and is rarely completely eradicated. Asphalt shingles do not hold up well once moss gets underneath them. If the roof is cleaned regularly and preventive measures are taken, the shingles will hold out much longer.

Clean the shingles of all roof types by first brushing away surface moss. Use a bristle brush attached to a pole (available at home improvement stores), and either stand on a ladder and reach up, or climb onto a non-mossy spot of the roof (always wear a safety harness if working on the roof, and have a partner with you). Brush downward, not upward, to dislodge the materi- al and prevent it being shoved underneath abutting shingles.

Apply a nontoxic roof cleaner to the affected area. Oxygen bleach (not chlorine bleach) is one recommended product to kill moss and algae on wood or asphalt roofs. Rinse thoroughly, protecting any plants below by covering them with a tarp.

To prevent the problem from recurring, you must create an unfriendly environment for moss. First, have a professional tree specialist come and thin out the branches of your butternut tree, to allow more sunlight to filter through (this has some added benefits - improving the health of the tree and lessening the chance that it will topple onto your house in a windstorm).

Second, apply thin copper or zinc strips (about 3-4 inches wide, available from roofing suppliers) near the top of the roof, sliding one edge under a row of shingles and tacking into place. These metals discourage plant life from taking hold (and you thought copper roofs were just decorative).

HOME TIP: Some asphalt shingles today have copper mixed into the small granules of their top surfaces to retard moss and algae growth. When it's time to redo your roof, ask for this type of shingle. It's more expensive, but perhaps worth it in the long run.

Send questions or homerepair tips to homeguru2000@ hotmail.com, or write This Is a Hammer, c/o King Features Weekly Service, P.O. Box 536475, Orlando, FL32853-6475.

(c) 2007 King Features Synd., Inc.