Knowledge
Commercial Roofing Glossary
Every term defined in plain English first, technical detail second — so you can read a contractor proposal, warranty, or inspection report without a translator.
- Flashing
- The waterproofing detail work where a roof meets anything that is not roof — walls, curbs, pipes, drains, edges. Roofing professionals widely treat these transitions as the most leak-prone part of a roof.
- Fully adhered
- A membrane attachment method in which the roofing sheet is continuously glued to the substrate rather than fastened or ballasted — no fastener rows, no membrane flutter.
- Mechanically attached
- A membrane attachment method using rows of screws and plates driven through the membrane edge into the roof deck, with fasteners hidden inside the seams.
- Mil (membrane thickness)
- One thousandth of an inch — the unit used for single-ply membrane thickness. Commercial single-ply membranes are commonly produced in 45-, 60-, 72-, and 80-mil thicknesses.
- Parapet
- The part of a wall that extends above the roof line. Parapets concentrate flashing, coping, and edge-securement details, making them a standard inspection priority.
- Ponding water
- Water that remains on a roof surface more than 48 hours after rainfall ends — a leading accelerant of membrane aging and a common warranty exclusion.
- Positive drainage
- A roof design condition in which slope is sufficient to drain all water from the roof surface within 48 hours of rainfall under normal conditions.
- Scrim
- The reinforcing fabric layer inside a single-ply membrane. Polymer above the scrim is the weathering surface; when weathering wears down to the scrim, the membrane is at or near end of life.
- Scupper
- An opening in a parapet wall or roof edge that allows water to drain off the roof, either directly or into a downspout — often the overflow protection required by code.
- Square (roofing)
- A roofing industry unit equal to 100 square feet. A 20,000 sq ft roof is 200 squares — bids and material quantities are often stated this way.
- Wind uplift
- The suction force wind creates as it accelerates over a roof, strongest at corners and perimeters. Roof assemblies are engineered and tested against calculated uplift pressures by roof zone.