The Purpose of Stone or Gravel Ballast on a Flat Roof

It is not unusual to find a gravel top coat on commercial roofing systems. Though primarily confined to built-up asphalt roofing systems, it can be applied to single-ply EPDM, rubber-based membranes as well. These small stones are worth more than their weight in the protection they offer for underlying roofing materials and the barrier they provide to external elements like ultraviolet rays and harsh weather elements. Both factors can extend the life of your flat roof.

Specifically, there are two main reasons to use a ballasted roof system:

  • The weight provided by the gravel is used to anchor down the roof materials, therefore using far fewer fasteners to hold the materials to the decking. The gravel can be applied in far less time than using a specially designed screw and plate fastening pattern.
  • The ballast is used to keep the roofing system cool and of out of the sun’s harmful rays, thus keeping energy costs down. The gravel top coat is also extremely resilient to heavy foot traffic and high-wind scenarios.

Despite the positive qualities associated with a ballasted roof system, there are some challenges. It is very important to note that the amount of gravel being applied to a roof must be precise—it depends on the specific roofing spec being used and the building type. Too much gravel can result in a structural issue due to weight. Generally, the weight for a gravel-coated roof must be within 10-25 pounds per square foot.

Finding a leak in a sea of gravel can be very difficult—even more difficult if the gravel has been set in a layer of hot asphalt. The fact that the gravel collects dirt and moisture can make patching the leaks just as difficult once they have been located.

Though not as common as they used to be, ballasted roof systems still prove to be a viable solution for today’s commercial roof needs.

To learn more about selecting a commercial roofer in Cleveland, Ohio, simply fill out the form on this page and a member of our team will be in touch. Or, you may call us at 440.946.2233.

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