If you’ve ever rented a power washer, you know it does an amazing job cleaning concrete, wood, and other materials. You may have even been tempted to clean your roof with it.
Before you do, you had better be sure you know whether you have shingles on your roof or some other roofing material.
What causes black streaks on roof shingles?
If you look at your roof and you see something that looks dirty, it could be mold or algae. That’s very common throughout the United States, but moist places like Georgia or Alabama have it the worst. They have more moisture than we do in Oklahoma.
What happens is that a lot of shingles in the olden days did not have an algae-resistant metal like copper mixed in with the granules of the shingles. So older shingles have a tendency to develop those black streaks over time. That’s usually when the roofs are 12-15 years old.
Why don’t we see that often in Oklahoma?
There are a few reasons we don’t usually see that kind of growth on roofs in Oklahoma.
In places like Georgia, Alabama, and Mississippi they have tall pines. So even though it gets hot there, it’s still often muggy, so there’s a lot of algae growth compared to Oklahoma.
Here you have 105 degree temperatures during the summer and sunlight directly on your roof, so often the algae gets burnt off. I’ve seen roofs in other states where they not only had algae, but lichens and other growths as well. Fortunately, we don’t have that issue here in Oklahoma.
The other major reason is because our roofs just don’t last long enough for there to be an issue. We have far more hail storms than many other areas of the country.
So why is pressure washing a roof bad?
If your roof has some sort of tile on it, you can clean those. You can pressure wash them and clean it up. I’ve done that to roofs in Florida. It really takes that kind of pressure to knock the mold and mildew off.
But actual roof shingles are made of granules on asphalt. You can’t pressure wash that! You’d be blasting those granules off of the asphalt. It would most likely ruin your shingles during the process.
Keep in mind that the algae itself will not damage the roof. Sure, it looks bad. But it’s just dirty.