parklandWhen your commercial roofer talks about repairs or replacement of your Oklahoma City’s low-slope roof, do you understand what you hear? Learning some of the language of low-slope commercial roofing makes you more knowledgeable, makes the conversation more meaningful, and helps the roofer know your precise concerns.

Low-Slope Commercial Roofing

A low-slope roof is usually defined as having a pitch—rate of drop—of three inches or less for every 12 inches of horizontal measure. So a “3-in-12” roof slopes three inches for every foot of run. Residential buildings usually have much steeper pitches and use shingles or tiles. Low-slope roofs for Oklahoma City businesses have to be absolutely watertight, since water may pond on their surfaces.

Three Commercial Roofing Choices

  1. Built-Up Roofing (BUR)—This is a membrane made from mopping out hot bitumen over layers of asphalt-saturated roofing felt (tar paper).
  2. Modified Bitumen Membrane—This is a composite roofing membrane made with a reinforcing sheet coated on one or both sides with asphalt modified by the addition of a polymer.
  3. Ethylene Propylene Diene Monomer (EPDM)—A single-ply membrane made from synthetic black rubber, in which seams are held together by contact adhesive; often updated using white materials that provide greater energy efficiency.

Commercial Roofing Terminology

  • Asphalt—Bituminous material made by distilling crude oil.
  • Bitumen—Mixtures of thick, viscous hydrocarbons used as adhesives and waterproofing agents.
  • Cant Strip—A triangular-shaped wood or fiberboard strip that forms a transition for membranes from horizontal to vertical surfaces.
  • Cap Sheet—The upper ply of two-ply modified bitumen membrane.
  • Emulsion—Bitumen in water, held in suspension by an emulsifier. The evaporating water leaves the bitumen particles cemented together.
  • Curb—A metal or wood piece surrounding roof openings or supporting mechanical equipment allowing the waterproofing membrane to run up at least seven inches above the roof surface.
  • Edge Lap or Side Lap—The overlap of one ply’s edge over the previous ply, increasing waterproofing.
  • Membrane–A continuous flexible or semi-flexible waterproof sheet or surface; membranes can be single-ply or multiple layers.
  • Parapet—The low wall at a roof’s edge extending above the roof surface.
  • Ponding—Water accumulating in low spots on a roof.
  • Roof Jack—A cone-shaped metal flashing surrounding roof penetrations, such as chimney vents and plumbing pipes.
  • Scupper—An opening through a parapet or wall, permitting water drainage from the roof.


This is far from a complete list of commercial roofing vocabulary but it gives you a good start when you need to talk to a commercial roofing contractor. For more help understanding your Oklahoma City business’s low-slope roof, contact Perfection Roofing.

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