51 W. End Trail #552
Macungie, PA 18062
Hydro Scrub provides pressure washing services to Berks, Bucks, Lehigh, Montgomery, and Northampton Counties, including the cities of Allentown, Bethlehem, and Whitehall, PA.
We are now closed for the season. Have a happy, healthy and safe Holiday season.
Q… My roof is showing a stain that looks like mildew. What is causing this? Can I easily remove the stain? Can it be prevented?
A… In most cases, the stains and streaks are a form of algae called Gloeocapsa magma. This is a very hardy algae. The streaking and discoloration is an accumulation of the algae's dead, dark-colored cells. While this algae can grow just about anywhere in the continental USA, it prefers humid environments and usually first shows up on the north slope of a roof where shade is present. The algae was probably deposited on your roof by wind and/or wildlife. Gloecapsa magma was somewhat uncommon in the Lehigh Valley until about 2000. Since that time, the amount of roofs displaying staining from the algae has increased significantly. Prior to 2002, Hydro Scrub was rarely called to perform roof cleaning services, now it is a common service for us.
So what caused the problem? Today's new fiberglass shingles are quite different from old shingles because they contain ground limestone, used as a filler to increase the weight of the shingles so they are less prone to wind damage. The algae probably invaded your last roof as well, but it starved to death because it had different materials as its host environment. Gloeocapsa magma loves to eat limestone, and hence, proliferates on the newer fiberglass shingled roofs.
The algae can be prevented by introducing copper or zinc to its environment (your roof) which kills the algae. These metals serve as a very effective poison to the algae. This is the same reason why copper is often added to aquariums…to control algae blooms. If your roof is still quite new, you can install some copper strips along the roof ridge which will allow acid based rain to wash down small amounts of copper to poison the algae and prevent its growth. If you wish to proceed with such a protocol, consider installing long, 7-inch-wide strips of copper underneath the full course of shingles at the top of your roof. You should be able to slide the copper up under the shingles approximately 5 inches or so. This will leave approximately 2 inches exposed to the weather. It will take some time for the copper to kill off the alage…do not expect immediate results….months will be required. Additionally, note that some sources suggest that while this method may work well, in some cases it may be less than 100 percent effective. Hydro Scrub has cleaned customers' roofs to remove Gloeocapsa magma and the customer then installed galvanized (zinc) metal strips as a protective means…no roof staining has resulted for numerous years for this client.
If you are getting ready to install new shingles, you need not install copper strips as explained above. Many fiberglass shingles are now available with colored granules that contain metallic copper. There are enough granules present on each shingle to kill the algae. The copper is slowly released over time. Many of these shingles are guaranteed to kill the algae for the life of the shingle.
There are two other options to remove the algae from your roof, depending on your desires and budget. The first method involves the application of cleaning solutions to your rooftop, letting the solutions dwell for a bit and then low pressure rinsing the roof surface to remove the stains. This is called soft power washing. This method results in an immediate improvement in the appearance of Gloeocapsa magma stains and is often required for severely stained roofs. However, if the pitch of your roof is excessive and therefore "not walkable", this option may become quite expensive as an aerial lift will be required to provide safe access to your roof. Walking on a steep, wet roof, with soap solutions is not the same as walking on a dry roof.
The other option to clean your roof of stains involves the application of a "specialty cleaner" to a dry rooftop which, over a period of several months, will kill the algae. The downside to this method is that it takes quite a long while to see an improvement...just like the copper/zinc strips. No pressure washing is required with this method, but safe access to the roof which permits the application of the "cleaner" must still be made. Usually this can be accomplished from a ladder since no "walking" on the roof is required.
If your roof is susceptible to Gloeocapsa magma, routine maintenance will be required to keep it free of the algae. Either placement of copper/zinc strips or the application of the "specialty cleaner" on intervals of 18 to 24 months will be required.
Finally, before undertaking a roof cleaning project, make sure that your shingles are in satisfactory condition. We do not advocate cleaning shingles that truly need replacement. If you are not certain if your roof needs just a cleaning or if replacement is warranted, here are some indications of an aged roof:
• brittle or crumbling shingles,
• excessive amount of shingle granules in your gutters,
• bottom corners of shingles curled up,
• wavy, warped, or heaved shingles, and
• very thin or loose shingles.
If you have any specific concerns, please feel free to contact us to discuss your roof cleaning or roof washing project.