Roofing contractor glossary

Short, plain-English definitions of the terms you'll meet when choosing a roofing contractor provider in Georgia.

What are 3-tab shingles?: 3-tab shingles are basic single-layer asphalt roof shingles with three uniform tab cutouts per strip, designed as an economical roofing option with a flat appearance.
What are architectural shingles?: Architectural (or dimensional) shingles are laminated asphalt shingles with multiple layers that create a textured, three-dimensional appearance, offering better durability than traditional 3-tab shingles.
What is a Class 4 impact rating?: Class 4 is the highest impact resistance rating under UL 2218, indicating a shingle can withstand 2-inch hail without significant damage and qualifies for insurance discounts in Georgia.
What is a low-slope roof?: A low-slope roof has a pitch below 3:12 inches of rise per 12 inches of run, typically found on commercial and industrial buildings, and requires weather-tight membranes rather than overlapping shingles for water shedding.
What is a ridge vent?: A vent system installed along the roof ridge line that allows hot and moisture-laden air to escape from the attic to the outside.
What is a roofing square?: A roofing square is 100 square feet of roof area, the standard measurement unit contractors use to calculate shingle quantities and material costs for estimates and bids.
What is a standing seam metal roof?: A metal roofing system in which vertical seams between panels are raised above the roof surface and fastened from underneath, leaving no exposed fasteners or penetrations on top.
What is a wind uplift rating?: A wind uplift rating is a measurement in pounds per square foot (psf) indicating how much upward wind force a roof system can withstand before materials or connections fail.
What is built-up roofing?: Built-up roofing (BUR) is a flat roof system made from multiple layers of tar-saturated felt, fiberglass, or polyester alternated with hot asphalt, finished with a gravel or stone surface.
What is drip edge?: Drip edge is a metal strip installed along the eaves and rakes of a roof to direct water away from the fascia board and underlying deck structure.
What is EPDM roofing membrane?: EPDM (ethylene propylene diene monomer) is a synthetic rubber single-ply membrane installed as a waterproofing layer on flat or low-slope commercial roofs.
What is exposed fastener metal roofing?: Exposed fastener metal roofing uses metal panels where screws penetrate through the visible panel face to attach to the roof deck, creating attachment points that are exposed to weather.
What is Galvalume?: Galvalume is a metallurgical coating of aluminum and zinc applied to steel sheets used in metal roofing to resist rust and environmental corrosion.
What is gauge in metal roofing?: Gauge is a standardized measurement of steel thickness in metal roofing panels, expressed as a number where lower numbers indicate thicker, stronger material.
What is ice and water shield?: Ice and water shield is a self-adhesive, rubberized waterproof membrane applied to roof decks that creates a secondary water barrier at high-risk areas prone to ice dams, wind-driven rain, and flashing leaks.
What is Kynar 500 coating?: Kynar 500 is a polyvinylidene fluoride (PVDF) resin-based coating applied to metal roofing panels to provide superior color retention and UV fade resistance.
What is modified bitumen roofing?: Modified bitumen roofing is asphalt-based roll roofing reinforced with polymer modifiers, installed either by torch-down heat application or cold adhesive methods on flat and low-slope roof surfaces.
What is roof decking rot?: Roof decking rot is the breakdown of the plywood or oriented strand board (OSB) sheathing layer beneath roofing material due to prolonged moisture exposure and fungal growth.
What is roof decking?: Roof decking is the structural layer of plywood or oriented strand board (OSB) that sits on top of the roof trusses and serves as the base to which shingles, metal panels, or other roofing materials are fastened.
What is roof flashing?: Metal strips or sheets installed at joints, valleys, chimneys, and wall intersections on a roof to seal gaps and redirect water away from vulnerable areas.
What is roof pitch?: Roof pitch is the angle or steepness of a roof, expressed as the ratio of vertical rise to horizontal run (for example, 6:12 means 6 inches of rise for every 12 inches of run).
What is soffit and fascia?: Soffit is the horizontal underside of a roof overhang, while fascia is the vertical trim board that runs along the roof edge and supports gutters and gutter systems.
What is TPO roofing membrane?: TPO (thermoplastic polyolefin) is a white or light-colored synthetic rubber membrane installed as a single layer on low-slope commercial roofs, with seams bonded by heat welding.
What is underlayment?: A protective moisture barrier material installed directly on the roof deck beneath shingles or panels to block water penetration and provide secondary weatherproofing.