What are those awful stains on my roof?

Bob and Penny Hall — Thu, 22 Mar 2007 19:31:37 +0000

ANSWER: A plague that infects homes in nearly 80 percent of the United States, including Chesapeake Bay homes – Gloeocapsa Magma.

Gloeocapsa Magma is a species of algae that causes black streaking and discoloration on asphalt/fiberglass shingles. The black staining is caused by the growth of algae and fungus spoors that land on houses. The streaks and discoloration you are now seeing is an accumulation of their dead, dark colored cells.

Trees do not have to be present for this air-born menace to set up camp on your roof. This alga produces its own energy source and feeds on inorganic materials, such as the materials in shingles. All they need to grow is the nutrients from both the dirt on your roof and the limestone granules on the shingles. Heat and moisture help them turn your whole roof black.

An alga is an organic material and feeds only on inorganic material. Fungus and mildew need organic material to survive. So if you can reduce the algae on your roof, you will also reduce the growth of fungus and mildew. Keeping your roof free of twigs, leaves, and other
debris will also help reduce the growth of fungus and mildew. Cleaning and controlling algae and fungus growth can add to the life of your roof.

Roof shingles come in a wide variety of quality levels. The higher quality shingles have been treated to prevent algae and fungus growth. This treatment consists of adding varying amounts of copper and zinc granules and petroleum distillates to the shingles.

If you clean the roof yourself, be careful of products that are just bleach or chlorine. Using these can leave your roof streaked. It also can dry out the shingles and cause premature cracking. Strong cleaning solutions will also kill grass and shrubbery. Look for deck cleaners that contain bleach such as oxygen bleach, a non-toxic powder that mixes with water.

Wait for a cool, overcast day to apply the oxygen bleach solution. Do not let the solution dry. After it has soaked for 30 minutes, brush the solution with a stiff broom or brush. Always aim the rinsing hose down the roof, not up under the shingles.

Resist the advice of your neighbor to rent or buy a pressure washer. This common method of washing and scrubbing may get rid of the algae temporarily, but it will also damage the shingles.

If you “don’t do” roof cleaning, (as our grandchildren say), call a qualified roof cleaning company. But you still need to ask if the products they use will cause streaking or grass and shrub damage. Roof cleaning companies can also provide preventative maintenance services that can prevent future algae and fungus growth.

Venting Your Home’s Crawlspace

Bob and Penny Hall — Fri, 15 Dec 2006 16:14:51 +0000

Winter is coming and it’s time to review the popular but unwise practice of closing the foundation vents around a home. Many homeowners and maintenance people do this in the belief that they are conserving heat during winter. Instead, they are causing serious building damage and heath problems. Unfortunately, many hardware stores sell products specifically made for closing the vents, adding to the confusion of this potentially harmful misconception.

Closure of crawlspace vents is definitely a widespread problem. As a means of winterizing a home, it misses the entire purpose and intent of ventilating the area. Winter is when ground moisture most commonly occurs under a building. It is the time of year when vents are most needed to prevent dampness, condensation, and resultant moisture damage. Closing the vents wrongly assumes that there is a need to retain heat in the sub area. Instead, heat should be retained within the dwelling by installing insulation in the floor framing. The sub area needs to be dry, not warm.

A power vent system, in addition to improving venting and moisture removal, serves to vent out other gases, such as those formed from residues in termite treatment, treated wood, and radon gases. They are available for approximately $100, a small expense for the protection gained.

The key points to consider are these:

1. Typically, local building codes require cross ventilation of a sub floor space beneath a building, with openings equaling at least one square foot per 150 square feet of floor area. Exceptions are allowed when a vapor barrier is installed on the ground surface or when mechanical ventilation is provided

2. Insufficient ventilation can cause moisture condensation, resulting in fungus infection, dry rot damage, rusted hardware and mold infestation. With mold as a consideration, we are therefore concerned with health safety as well as structural damage.

3. Insufficient ventilation can also violate combustion air requirements for fuel burning equipment, such as furnaces.

Chesapeake Bay Real Estate » Home Maintenance

What are those awful stains on my roof?

Venting Your Home’s Crawlspace