Plenty of cleaners can tackle stained, shingled roofs
Q: Our shingled roof is stained with fungus or algae and we want to clean it. What are suitable cleaners and cleaning methods?
A: What to do about roof stain is probably the question most-asked of this column.
Stains range from dark streaks of algae or fungus to patches of moss, and they are most common in regions of high humidity and on roof areas that get little sunlight. They most often affect roofs with asphalt shingles.
Among cleaners often used on roofs are Shingle Shield Deck and Roof Cleaner ( www.shingleshield.com); Roof Mold Cleaner OX ( www.cleanertoday.com, click on Roof Cleaner); Jomax Roof Cleaner ( www.zinsser.com); and solutions of chlorine bleach and TSP (often a quart of bleach and a tablespoon of TSP to a gallon water).
TSP is a heavy-duty cleaner sold at most paint stores. Some home centers also sell roof cleaners.
A garden-type compressed-air sprayer is the best applicator for cleaners, and rinsing should be done with a forceful stream of water from a garden hose.
Chlorine bleach, an ingredient of some roof cleaners, should be rinsed off after no more than about 15 minutes or the bleach might cause shingle damage.
Pressure washing, once a common method of cleaning roofs, should be avoided because a high-pressure stream of water can dislodge protective granules from asphalt shingles and damage wood roofs. If used at all, pressure washers should be set to no more than 500 psi.
Working on a roof is obviously hazardous and the hazard is increased when the roof is wet and slippery, as it is during cleaning.
If possible, work from a ladder, which has its own hazards if the ladder is not properly anchored and used. Do-it-yourselfers not skilled in roof work should leave the job to a roofing contractor.
If climbing on the roof can’t be avoided, a safety harness will give some protection. It should include a strong rope attached to a tree or heavy vehicle on the ground and on the opposite side of the roof from the side being worked on, so that the rope will break a possible fall.
Q. My stucco siding has a number of small cracks that I’d like to patch. The largest cracks are about 1/8-inch wide. Can you help?
A. Small cracks like these can be patched with caulking compound. A silicone caulk is fine if you can find one with a color that matches your stucco; otherwise choose a paintable acrylic-latex caulk so you can touch it up to blend in with the stucco.
If your stucco has a sandy texture, as most do, you can approximate the texture by squirting some caulk into a paper cup and mixing a little sand with it, then forcing it into the cracks with a putty knife. Special stucco patching compound is also available.
One of these is Quikrete’s Stucco Crack Repair, sold in toothpaste-type tubes at some home centers and building-supply outlets. This is an acrylic compound that has some built-in texture to help it blend with the stucco, but it is available in white only and must be painted to match colored stucco.
For more information, visit www.quikrete.com; click on Products, then scroll down the product categories to Caulks and Crack Sealants.
Q. Do you know of an environmentally safe solution for killing grass in driveway cracks?
A. Full-strength white vinegar will kill some types of grass and many weeds and is the most environmentally safe solution I know about. Put some in a spray bottle and soak the unwanted grass on a day when no rain is expected.