Top 10 No 8

Low-Slope Roofing Mistake No. 8: Missing Cut Edge Sealant

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Cutting the edges of a reinforced membrane, whether on the roof or in the factory, exposes the reinforcement scrim to the elements. It’s important to apply Cut Edge Sealant to all of those exposed edges within 24 hours of installation. Otherwise, water can wick into the exposed scrim. 

In this segment of the Roofing it Right with Dave and Wally miniseries on the Top Ten Mistakes in Low Slope Roofing, GAF Senior Commercial Training Specialists Dave Scott and Wally Brown discuss which edges need sealant and which don’t:

DO need sealant (or to be buried under another layer)

  • Reinforced membrane cut on the roof and ends of membrane rolls 
  • Reinforced accessories on the roof

DO NOT need sealant 

  • Unreinforced accessories such as T-joint and corner patches

Remember to probe your seam before applying cut edge sealant.

Check out the episode here:

And be sure to check out the entire top ten list, along with the complete collection of entertaining and educational Roofing It Right episodes (muchos de ellos disponibles en español), at

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