The constant exposure to the elements puts every roof at risk to stains. Pooled water and moisture leads to stains on commercial roofing. The most common signs of stains are lichens, moss, and algae. These microorganisms can grow in moist conditions such as when rain gets trapped in roof cracks. Any collected debris only further adds to this ideal environment. If cracks are ignored and water is allowed to collect or enter the roof membrane, the risk of algae or moss growth increases. You will likely start seeing stains as a result. Every roof is vulnerable to stains, so you need to know how to remove these stains and how to prevent them.

How To Remove and Prevent Roof Stains?

DIY Stain Removal

It is possible to remove any stains on the roof yourself. This can help save on costs, especially with larger roofs. If you do decide to take on the job yourself, make sure you have precautions in place and are safe, as working on commercial roofing can be dangerous.

  • To clean roofing stains, you will need the right materials.
  • Non-corrosive cleaner
  • Pump sprayer to distribute the cleaner
  • Hose with spray nozzle (for larger roofing, make sure you have a hose that can reach all areas on the roof)
  • Safety glasses or goggles
  • Rubber gloves
  • Ladder and safety rope or harness
  • Slip-resistant shoes
  • Plastic sheeting (if you have plants or shrubs near the building, you will want to cover them from any chemicals that run off the roof)

Save roof cleaning for a cooler day, ideally with some cloud cover. You also want to make sure there is no wind. This will help maintain control over the water spray as you will need to target areas where the stains are set.
Cleaning away stains without the heat of the sun also allows the cleaning solutions to soak in properly. This makes removing stains much easier. Apply the cleaner until the stained area is saturated and should any areas dry out, re-apply the cleaning solution. Before you start, make sure all areas with stains are properly prepped. All gutters and drainage areas need to be cleaned and free of blockage. This makes sure that all the cleaning products and removed debris can drain away from the roof properly.

Professional Stain Removal

You can also choose to hire a professional roofing company to clean the stains for you. When you go with this option, the most common methods of stain removal involve:

  • Low-pressure cleaning: Eco-friendly cleaning solutions are used and high-quality equipment removes stains quickly and effectively. This method is perfect for aging roofing that may have weaker integrity as it is a gentle cleaning process.
  • Bleach: Chlorine bleach (sodium hypochlorite) is made into high concentration cleaners and is sprayed across the roof, and allowed to dry. The bleach breaks up the stains and removes them, so this method takes time. It is more affordable than other cleaning options though.

Preventing Stains In The Future

Now that you have the algae or stains removed, you don’t want them coming back. While you cannot control this outcome entirely, there are things you can do to reduce the change of algae or moss growth. Copper is toxic to algae so can be used as preventative measures. A strip of either metal can be installed along the side of your roof. You can use roofing nails to attach the strips and this will help eliminate algae growth and reduce roofing stains. Copper is the most toxic to algae but can be expensive, so galvanized metal will also work if you have a budget.

Final thoughts

Stains are inevitable at some point even with regular maintenance. Knowing how to safely remove it and prevent it will keep your roof in its best condition. Taking the time to remove all algae, moss, or mold when identified is the best preventative measure. With a regular inspection schedule, you can spot these issues before they grow out of hand. Reach out to us for any inspection or roof cleaning needs you may have for your commercial property.


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