How To Get Rid of a Fungi-Stained Roof

Q: Our shingled roof is stained with fungi or algae, and we want to clean it. What are suitable cleaners and cleaning methods? -- V. Eicher

A: What to do about roof stain is probably the most commonly asked question of this column. The stains range from dark streaks of algae or fungi to patches of moss, and they are most common in regions of high humidity and on roof areas that get little sunlight. The stains most often affect roofs with asphalt shingles.

Among cleaners often used on roofs are Shingle Shield Deck and Roof Cleaner (http://www.shingleshield.com), Roof Mold Cleaner OX (http://www.cleanertoday.com; click on "roof cleaner"), Jomax Roof Cleaner (http://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 because the bleach could 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.

If possible, work from a ladder. This can have 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? -- C. Kelly

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 that 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 compounds are also available. One of these is Quikrete's Stucco Crack Repair, sold in toothpaste-type tubes at some home centers and building-supply stores. 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 http://www.quikrete.com.

Q: Do you know of an environmentally safe solution for killing grass in driveway cracks? -- H. Cooke

A: Full-strength white vinegar will kill some types of grass and many weeds and is the most environmentally safe solution that I know about. Put some in a spray bottle, and soak the unwanted grass on a day when no rain is expected.

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QUICK TIP: Electrical cables around your computer, television set or other equipment can be kept in neat bundles with a few turns of vinyl electrical tape (not cloth-backed tape). Vinyl tape stretches enough to hold the wires securely but can be easily cut or peeled when wires are added or removed. Vinyl electrical tape is also excellent for bundling unused appliance cables and extension cords. The tape is sold in rolls at most home centers and hardware stores.

Questions and comments should be sent to Gene Austin, 1730 Blue Bell Pike, Blue Bell, Pa. 19422. Send e-mail to doit861@aol.com. Questions cannot be answered personally.