Real estate

Ask the Carpenter

They want to move out, but a fungus has moved in

There are companies out there that will clean and kill roof algae safely without a pressure washer.
val lawless/shutterstock
There are companies out there that will clean and kill roof algae safely without a pressure washer.

Q. Our 21-year-old house has its original roof. We’ve been fortunate not to have experienced any leaks except one time years ago after a very windy rainstorm. A local roofer repaired the problem at minimal cost. Ever since then, however, there has been streaking from algae, fungus, and lichen, which will really detract from the curb appeal when we go to sell the house. We got an estimate to replace the roof on just the front, but we are considering our options:

1. Replace the entire roof;

2. Have it professionally cleaned;

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3. Do nothing and let the new owners deal with it.

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I am leaning toward leaving it as is as the smartest and least expensive choice, but improving our home’s curb appeal would increase the selling price.

CINDY BOLTON, Ashland

A. I wouldn’t replace it. There are companies out there that will clean and kill roof algae safely without a pressure washer. The Asphalt Roofing Manufacturers Association and suppliers such as GAF and Owens Corning have suggested commercial-grade cleaning methods and solutions to clean roofs of algae. It is a bleach-based solution with copper oxide and zinc phosphate that goes on with a garden hose. Some companies also use a detergent algicide.

Once your roof is clean, use this trick I learned from the late Peter Hotton, who wrote the Globe’s Handyman on Call column. Install zinc strips just below the ridge cap to prevent the growth of algae, moss, and lichen. Rain carries the zinc particulate down over the shingles. On the negative side, direct runoff carrying zinc can harm vegetation and water supplies, so be careful where you put those strips.

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Q. We want to replace the carpeting in our house. Our dog has had a number of accidents, and the urine has gone through the padding to the floorboards. What should we do to the floors before putting down new carpet?

KAREN

Get some doggie diapers first! Seriously, the best fix is to replace the subfloors. If that is not in your budget or for some other reason not feasible, apply a couple of coats of Zinnser primer sealer or polyurethane. Also replace or seal the baseboard trim and any wallboard as needed. If you choose to seal the subfloor, use a -inch nap roller and apply liberally.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @globeaddress or @robertrobillard.