Here is a checklist of warning signs that indicate a troubled roof:
Ceiling Spots: Water spots on the ceiling are often caused by leaks in the roof. There are many places you should look to find the source of the problem. Check the roof for damaged or missing shingles, the chimney and vents for cracks in flashing, the eaves for water backing up from ice dams, and the rafters for leaks that travel away from the source.
Damaged Flashing: Flashing are pieces of metal or roll roofing around vent pipes, chimneys, adjoining walls, dormers, and valleys used to prevent water from seeping in. Damage to the flashing can be caused by improper installation or by drying and cracking. Flashing can sometimes be repaired without replacing the roof.
Missing Shingles: Missing shingles are often caused by exposure to high winds and improper fastening, but usually can be replaced individually. If you decide to re-roof, you might consider shingles that are specially designed to stand up to strong winds like Owens Corning’s new WeatherGuard® High Wind 110 Roofing System.
Buckling and Curling: When a shingle buckles, it bends upward in the middle, forming a peak. Buckling is caused by improperly applied felt or by movement in the deck (the surface the roof is applied to). Curling causes the corners of the shingle to turn up. It is usually a result of a lack of ventilation, nails positioned too high up, an incorrect number of fasteners, or under-saturation of the shingle.
Blistering: Blisters are bubbles that appear on the surface of asphalt roofing. They are usually caused by moisture in the shingle or by applying the shingles over a wet deck.
Algae Growth: Algae growth shows up as a dark discoloration on the roof. It is found most often in warm, humid climates such as the Southeast but does not affect the service life of the roofing material. In areas where algae growth is most common, you might consider using algae-resistant shingles.
Missing Granules: Normally, a certain number of granules will be loose, especially after application. But on aging shingles this is often a sign that you need to replace the roof.
Rotting: Rotting shingles are caused when the mat at the core of the shingle absorbs moisture. It is a common problem with organic-based shingles.