Why is My Shingle Roof Staining?

In moisture prone climates throughout the United states, shingle roofs have a bad reputation for staining or streaking. This staining is caused by an algae growth called Gloeocapsa magma–a blue-green algae that thrives on the limestone granules found in many shingles. The streaking is most common on north facing roof slopes where less direct sunlight creates a better habitat.

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What is the difference between Blue-green algae and Moss

On some roofs that stay moist for extended times, moss grows in addition to the algae. Moss is a plant and will damage the shingles by causing gradual loss as its roots dig into the shingle. Alega, on the other hand, is a bacteria and is not as destructive, but still unsightly. This article focuses primarily on roof algae.

Why Does it Matter?

The primary concern for homeowners usually is the way staining detracts from the aesthetics or curb-appeal of their home. Most people judge a roof’s age by visual signs. A dark, stained roof looks like an old roof when in actuality the roof may be only 8-10 years old. If you're looking to list your house for sale, most homebuyers are concerned about two main things.  What is the condition of the roof and how old is the HVAC system? Unfortunately, if your roof is stained, the prospective buyer sees it as an older roof that may need to be replaced soon.


What Are the Solutions?


Clean your Roof

If your current roof is staining and it is not due for a replacement, consider a soft wash using these steps.

  1. Create a 4/1 solution using oxygenated bleach, water, and TSP (Trisodium Phosphate). It is important to use oxygenated bleach, not chlorinated bleach so you don’t kill your yard after you rinse it down the gutters.
  2. Apply this mixture to the roof surface and allow it to sit for 20 Minutes. It is important to choose a cooler day, to prevent your solution from evaporating too quickly.
  3. Rinse the solution using a garden hose (never a pressure washer!). Also, be careful. The roof will be slippery when wet.

After you rinse it off you will see at least some difference. The full difference may take some time to show as the bleach solution will kill the algae and your roof will further clean itself with time. If you have actual moss growth, you should use a scrub on these areas.

Replace your Roof

Likely cleaning your roof or paying someone to clean it doesn’t sound too exciting. You may be wondering if all shingle roofs are bad. Actually they are not. As with most any problem, good companies do research and develop solutions for these issues. If you're in the market for a new roof the solution to the problem of staining lies in the shingle brand you choose to have installed. Due to the extent of the algae staining problem, most shingle manufacturers boast some sort of “Algae Resistant Promise” on their shingle packages and brochures.

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So what are the best shingles for algae resistance and non-staining warranties?

In our experience, Atlas shingles have made the most significant progress in tackling the staining problem in the shingle markets. Atlas’ Pinnacle Pristine and StormMaster Shingles carry a lifetime non-prorated non staining warranty. If you read the fine print, this means that if your new Atlas roof stains in the first 25 years, they will replace it. If it stains in years 26 and on, they will cover the cost of a complete roof cleaning. This is the strongest non-staining warranty in the industry and is possible through the science of the way their shingle is made using a 10% blend of copper coated granules that release over time. Copper ions are acidic and prevent the growth of bacteria like the blue-green algae.

Unless you're in the market for a new roof, both cleaning and replacing might seem like difficult and unattractive solutions. If you're in the market already, your solution is simple. Evaluate carefully the shingles your contractor is offering. What is the non-staining warranty and what is the science behind that manufacturer’s claims? Be very cautious if the warranty is prorated after the first several years. Also, be sure to check on what is covered if it does stain while under warranty. Educating yourself now is your ticket to choosing the right shingle that will preserve your investment by keeping your home's curb appeal in addition to keeping it dry!

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