Stains on the roof aren't just unsightly; they can also spell serious roofing problems. As a homeowner, it's advisable to educate yourself on common roof stains and what they mean for your roof. That way, you will always know whether a stain requires the attention of a professional roofing contractor or whether it's something you can just wash away. Here are two crucial factors you can use to diagnose your roof stains:
This is probably the biggest clue you can use during stain diagnosis. Roof stains come in many different colors, but these are some of the most common:
These are usually caused by algae; specifically, the Gloeocapsa magma algae. They feed on different things, including the limestone fillers used in asphalt shingles. Algae usually strike wet roof or roofs in wet climates. At the same time, they also keep the roof wet, which means they encourage rotting and corrosion of wood and metallic parts of the roof, respectively. You can get rid of the algae by getting your roof professionally washed.
Brown or Red Stains
Brown or red stains usually emanate from the corroded or rusted parts of the roof. You will usually see such stains around metal parts of the roof or on sections of the roof below such parts. Again, perpetually moist roofs are more susceptible to rust than dry roofs. Surface rust may not be disastrous, but it may get into the material after some time and weaken it.
The location of the stain may also point to its origin. If a small section of the roof is stained, then the problem is either originating in that area or on the part of the roof above it. For example, if a roof has black stains only around the chimney, then algae colonies are probably not the problem. Black stains around the chimney usually point to a defective chimney that is spewing soot on the roof. Brown stains on a section of the roof under a tree are probably caused by debris, such as leaves, from the tree.
Shape of the Stains
Lastly, the shape of the stains may also be useful in diagnosing their cause. For example, algae or debris stains usually occur in patches. However, black streaks of stains that seem to run down the roof probably come from bleeding shingles. This happens when the chemical constituents, which appear black, leach through to the surface and run down the roof. Fortunately, this problem is usually just cosmetic; you don't have to remove it.