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Q. We saw a news story recently about granite countertops giving off Radon gas. We have a granite kitchen countertop. I’m wondering what we should do. What do you think?
A. I too have heard that claim and the first time I heard it was over ten years ago. Radon is a naturally occurring gas generated by the decay of trace amounts of uranium found in the earth's crust. So it’s here to a greater or lesser degree depending upon the soil make up under our houses. It is an unstable gas that quickly breaks down and dissipates in the air. Elevated exposures to Radon have been linked to lung cancer. Radon is measured in units called picocuries per liter (pCi/L). A picocurie is one trillionth of a curie, which is the amount of radioactivity emitted by a gram of radium. The U.S. Environmental Protection Agency (EPA) has established 4.0 pCi/L as the standard for indoor air. That represents a figure that is twenty times the average Radon in the ambient outside air-- so it’s almost everywhere to some extent. I have researched the subject over the years and can’t find a shred of real scientific evidence to sound an alarm. Any outgassing from a finished granite countertop would be infinitesimally small. I can’t fathom the motives of anyone who would put that kind of nonsense out. Don’t throw your countertop in the trash.
Q. My mother-in-law has a home who' s roof is about three or four years old. The roof gets plenty of sun and there are no trees around the house. The problem is there is a black stain on the shingles. Is there anything I can put on the roof to clean the shingles without killing the lawn or her shrubs or damaging the shingles? The roof is about 8/12 pitch so walking on it is going to be tough for a non professional. The one other issue which she has is Turkey Buzzards that like to roost on the peak of the roof. They live in the woods near the house. Is there a way without spending a lot of money (and getting in trouble with the animal right's people) to keep them off the house.
A. The black stains you see are a common airborne algae that float around, land on the roof surface and get established between the tiny bits of gravel placed on the shingles, called the aggregate, and procreate. We get enough rain annually to keep the algae going and the lighter the shade of roof shingles the more apparent it becomes.
The stains can be cleaned off with a light bleach and water solution but since you say the roof is steep, rising eight inches vertically for every foot of horizontal space it covers, I don’t recommend you get up there to attempt the cleaning. Don’t even consider the word powerwash when contemplating a roof cleaning method. That will shorten the shingle life, if not outright destroy them if done t oo aggressively. There are contractors who offer roof cleaning and the web is full of brand name roof cleaners but the recipe I recommend for deck cleaning, one cup laundry bleach plus one quarter cup dishwasher detergent to gallon of hot water, works well too. Cover the shrubs and flower beds with plastic tarps because anything that will quickly kill the algae growth won’t do the landscaping any good either. After the roof is cleaned the only way to prevent future staining would involve something like placing a zinc strip just below the peak on both roof faces. Zinc ions wash down the roof during rain preventing algae, mildew and moss growth. You could probably install those for under a hundred dollars, not including labor. If your mother-in law is still in the house when reroofing time comes, in ten to twelve more years, specify shingles with copper and magnesium granules imbedded in with the aggregate to prevent the growths from starting. It’s a minor additional cost of shingle and prevents the need for cleaning. The buzzards are another story. For discouraging them I’d use a product by Bird-X® called Spikes Needle Strips - Polycarbonate. It comes in lengths up to about 100 ft. They might have other products that would work and you can get a free evaluation from them online. Your mother-in-law might object to the look of the spike strips on her roof peak but she may have t o choose that over the birds. My suggestion is to couple placing the spike strips at the same as the zinc strips. Stay off roof surfaces as much as possible, just walking on those shingles doesn’t do them any good and falling from the roof will ruin your day.