Clean shingles? Replace shingles? Ignore?

[Mike Warder]

Hey everyone, 

This roof is 8 years old and the shingles are quite an eye sore from all angles. My understanding is that the algae in the shingles can also destroy ththe shingles over time. I asked my property manager about cleaning them, and her roofer suggested replacing and quoted $1,100. Is replacing the way to go? If so, is that a reasonable quote?

[Kurt K.]

No need to replace the shingles with only a 8 year roof. I would try this first.

The less expensive solution is to spray wash the roof with a 50 percent mix of water and bleach to get rid of the algae. (No pressure washers, please. They're likely to damage the shingles.) Just be sure to wet your foundation plantings first, and rinse everything in clean water when you're done. Plants don't like bleach, and wetting them with plain water first protects them.

To keep the algae from coming back, insert 6-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles.

You can probably see this same principle working on roofs in your neighborhood. Look for chimneys with copper flashing; the areas directly below the flashing will be free of any algae stains.

The strips also work on roofs suffering from moss buildup. Just scrub it off first with a brush, then bleach as above.