What are the warning signs that my roof needs attention?

What can be done about the black streaks on my shingles?
(see ALGAE GROWTH in image)

Depicted below are symptoms that indicate your roof may need to be serviced or replaced. Click on any problem to learn what’s causing it and how to fix it. If your roof is in the last 20% of its expected life, you should probably think about replacing the roof instead of repairing it.

ALGAE GROWTH

Causes: Algae growth causes a dark discoloration on roofs. The algae are usually brown to black in color which results in a streaked, dirty looking rooftop. It can be mistaken for soot, dirt, or tree droppings, which typically produce only localized discoloration. It’s caused by the growth of air-borne algae which deposits spores on your roof. The good news is that algae growth does not affect the service life of your roofing material. It occurs most often in warm, humid climates such as the Southeast.

Recommendations: Discoloration of roofs caused by algae is difficult to remove, but may be lightened by spraying a diluted solution of chlorine bleach, trisodium phosphate, and water onto the roof. Solutions range from one cup TSP, one-gallon bleach, and four gallons of water, to one cup TSP and 2.5 gallons each of bleach and water. This solution can then be rinsed from the roof in 10 to 15 minutes. Do not scrub. Scrubbing will loosen and remove shingle granules. After spraying be sure to thoroughly flush the roof and the greenery around the home (grass, bushes, and shrubs) with water. The effectiveness of this type of cleaning may only be temporary, and the discoloration may recur. High-pressure washing is not recommended due to the possibility of removing shingle granules, thereby shortening the life of the Roofing System.

For a more permanent solution, re-roof with algae-resistant shingles. They are specifically designed to inhibit most algae growth for extended periods of time and are usually backed by some type of manufacturer’s warranty.

BUCKLING

Causes: Wrinkled or improperly applied over old, rough shingles Roof deck movement from absorbed moisture. Poor roof ventilation.

Recommendations: Remove the shingles that are affected. Cut the wrinkle in the felt or smooth the original layer of shingles and replace the new shingles.

Add ventilation to the attic space. According to most building codes, you need one square foot of vent area for every 150 square feet of attic floor space. The minimum is one square foot for every 300 square feet of attic floor space if space is balanced between the ridge and intake vents. A balanced ventilation system means that about 50 percent of the required ventilating area should be provided by vents located in the upper portion of your attic to serve as exhaust vents, with the remaining 50 percent provided by eave vents for intake.

CURLING

Causes: High nails. An improper number of fasteners per shingle. Lack of ventilation.

Recommendations: Check location and number of fasteners to ensure that the shingles are installed per the manufacturer’s instructions. If high nails are present, use a hammer to make the nail head flush with the top of the shingle.

DAMAGED FLASHING

Causes: Improper installation on a new roof. Drying and cracking on an old roof. Dented or bent by severe weather or extreme temperatures. Settling of the structure.

Recommendations: In most cases, it is only necessary to remove and replace the flashing and shingles around the damaged area.

MISSING GRANULES

Causes: Normally a certain number of granules will be loose, especially after application. These granules are called “riders” and are a normal result of the manufacturing process. Granule loss does not affect the service life of the shingles unless the loss is severe enough to expose the asphalt or fiberglass mat.

Recommendations: On aging shingles, missing granules indicate a need for replacement. Following a hail storm, a sudden increase in granule loss is an indicator of possible hail damage.

MISSING SHINGLES

Causes: Improper fastening. Exposure to high winds.

Recommendations: Replace shingles that have completely blown off. Remove and replace shingles that have broken tabs.

For shingles with tabs blowing up and down, hand seals the shingles with an asphalt plastic cement, commonly referred to as flashing cement. This roofing cement must comply with ASTM D4586 — Type I or Type II which is the standard specification for asbestos-free asphalt plastic roof cement.

To hand seal, lift each tab of a 3-tab shingle and apply two spots of the cement under each tab. Each spot should be approximately the size of a quarter and placed 1″ to 2″ from each end of the tab and near the bottom. Laminated shingles require 4 spots of cement per shingle. After application, press the tab down firmly to start the bond. Be careful not to apply the cement too close to the bottom of the tab. This causes the cement to squeeze out when the tab is pressed down.

CEILING SPOTS

Causes: Spots are caused by leaks in the roof.

Recommendations:

Check attic for leaks in deck.
Check chimney and vents for cracks in flashing.
Check rafters for leaks that “travel” away from original source.
Check eaves for water backing up from ice dams.
Check roof for damaged or missing shingles.

ROTTING

Causes: Rotting is caused by the absorption of moisture by the mat at the core of the shingle. This is a common problem with organic-based shingles.

Recommendations: Replace with fiberglass mat shingles.

BLISTERING

Causes: Moisture in the shingle.