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Commercial Roofing Solutions from The Garland Company

Haunted by Chemicals, Bacteria and Grease on Your Roof

shutterstock_311604227It’s time for Halloween, time for screams and scares. But if you prepare your roof properly, at least you won’t have to be scared of contaminants destroying your rooftop.

For some buildings, the roof system protects against much more than just the natural environment. Many factories, restaurants and other specialized industries need additional protection against oil, grease, bacteria or other agents that can attack a building. Special conditions like these should be considered before choosing the roofing system.

Could your building be haunted by your environment, or that of your neighbor?

Oil and Grease

Modified bitumen roof membranes can be adversely affected by exposure to cooking oils (animal or vegetable) and grease. Membrane degradation typically occurs around exhaust vents, where the roof membrane has repeated contact with these contaminants. The organic substances contained in oils and grease weaken and eventually break down the polymer-bitumen network, causing premature degradation of the roof.

Bacteria and Fungus

Factories producing foods have reported cases of modified bitumen membrane decay due to bacteria. Such deterioration, which usually starts as “mud cracking,” may lead to the total decay of the modified bitumen membrane and surface coating. The degree of degradation is dependent upon the type of microorganism, temperature and other climatic conditions, and the composition of the bitumen. Fungus growth – most common in hot, humid regions – does not cause the same detrimental effects as bacteria and usually poses only aesthetic concerns.


Chemicals such as solvents, acids, bases, and oxidizing agents can cause varying degrees of harm to polymer modified bitumen roofing membranes. Non-polar solvents can temporarily swell and soften polymer-modified bitumen sheets, causing slumping and poor traffic resistance. They can also cause the polymers to separate from the asphalt. While polymer modified bitumen membranes have excellent resistance to various inorganic acids and bases, some of these chemicals may attack and degrade glass and polyester mats, as well as fillers like talc and limestone. Organic acids, such as acetic acid, are also known to have detrimental effects. Strong oxidizing agents can attack both the polymer and the bitumen in a membrane. Additionally, when ponding water is present, solid dusts can contribute to “mud cracking.” All of these effects may lead to premature failure of the roof membrane.


These effects can be prevented and sometimes avoided by planning ahead and taking precautions. Here are a few things to consider:

  • Wherever possible, reduce or eliminate exposure to contaminants.
  • Determine the types and concentrations of contaminants that may be present on the roof. When re-roofing, investigate what effects, if any, contaminants present had on the existing roof before specifying and applying a new roofing system.
  • Use commercially available traps and/or filters to prevent contaminants from being exhausted onto the roof.
  • Establish a roof maintenance program to monitor affected roof section and to properly maintain traps or filters.
  • Provide positive drainage (i.e., at least 1/4” per foot roof slope) to prevent ponding in the affected area.
  • Increase the number of plies and/or add resistant coatings to provide adequate protection.
  • Investigate alternate venting designs that minimize or eliminate contamination of the roofing membrane.
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