• Acrylic Roof CoatingA water-based elastomeric coating, usually white, applied to low-slope roofs for reflectivity and weather protection; generally not suited to ponding water.
• APP Modified BitumenModified bitumen membrane made with atactic polypropylene, giving a stiff, heat-resistant sheet that is normally torch-applied.
• Ballasted Roof SystemA low-slope roof in which the membrane and insulation are loose-laid and held down by the weight of stone or concrete pavers.
• Built-Up Roofing (BUR)A low-slope roof membrane made of several plies of reinforcing felt laminated with hot or cold bitumen, usually finished with gravel or a cap sheet.
• Cellular Glass InsulationRigid, closed-cell insulation made by foaming crushed glass, impermeable to water and vapour and able to carry heavy loads on roofs.
• Coal-Tar Pitch RoofingBuilt-up roofing that uses coal-tar pitch, a by-product of coking coal, as the bitumen, valued for slow ageing and limited to very low slopes.
• Cold-Applied RoofingRoofing installed without heat, using adhesives, cold-process bitumen or liquid resins instead of torches or hot kettles.
• CopingThe capping on top of a parapet or wall that sheds water and protects the wall and the roof membrane termination beneath it.
• Cover BoardA thin, firm board laid over roof insulation, or over an old roof, to protect it and provide a solid, compatible surface for the membrane.
• Cricket (Saddle)A small raised ridge built on a roof to divert water around a chimney, curb or other obstruction, or between drains on a low-slope roof.
• CSPE (Hypalon) RoofingSingle-ply roofing made from chlorosulfonated polyethylene, sold mainly as DuPont Hypalon; production for the Americas ended in 2010.
• EPDM RoofingSynthetic rubber single-ply membrane, usually black, joined with seam tapes or adhesives, and installed ballasted, mechanically attached or fully adhered.
• EPS (Expanded Polystyrene) Roof InsulationLightweight closed-cell insulation board made by steam-expanding polystyrene beads, widely used in flat and tapered form on low-slope roofs.
• Fully Adhered Roof SystemA low-slope roof in which the entire underside of the membrane is bonded to the substrate with adhesive or by heat, with no loose areas.
• Gravel-Surfaced Roof (Flood Coat and Gravel)A built-up roof finish in which loose aggregate is embedded in a thick top pour of hot bitumen to shield the membrane from sun, hail and traffic.
• GRP (Fibreglass) Flat RoofingA flat-roof covering of polyester resin and chopped glass-fibre mat laminated on site over a timber deck and finished with a pigmented topcoat.
• Hot-Melt Rubberised BitumenA thick, seamless waterproofing of polymer-modified bitumen melted on site and applied hot with fabric reinforcement, mainly for inverted, podium and buried roofs.
• Induction Welding (Roofing)Attaching single-ply membrane by bonding it to coated plates fastened to the deck, using an induction heating tool, so the sheet is not pierced.
• KEE Roofing MembraneSingle-ply membrane based on ketone ethylene ester, a high-molecular-weight polymer that keeps PVC flexible without migrating plasticisers.
• Liquid-Applied RoofingSeamless waterproofing formed by applying liquid resin by brush, roller or spray, often with a fleece or fabric reinforcement, that cures into a membrane.
• Low-Slope RoofA roof with only a slight incline, usually 2:12 or less, covered with a continuous waterproof membrane rather than overlapping shingles or tiles.
• Low-Slope Roof InsulationRigid board or sprayed insulation laid above the deck of a low-slope roof, chosen for long-term thermal value, strength, fire and moisture behaviour.
• Mastic Asphalt RoofingA traditional UK and European flat-roof waterproofing of hot bitumen and fine mineral aggregate, spread by hand into a seamless, monolithic layer.
• Mechanically Attached Roof SystemA low-slope roof in which the membrane is secured to the deck with screws and plates or bars, typically placed in the sheet laps.
• Mineral Wool Roof InsulationDense non-combustible boards of stone or slag fibres used as flat-roof insulation where fire resistance, acoustics or dimensional stability matter.
• Modified Bitumen RoofingFactory-made roofing sheets of asphalt blended with polymers such as SBS or APP and reinforced with polyester or glass fibre, laid in one or more plies.
• Overflow (Secondary) Roof DrainageEmergency drains or scuppers set above the primary drains so that water can leave a low-slope roof if the main outlets are blocked.
• Parapet (Roof)The part of an exterior wall that rises above the roof edge, providing fall protection, fire separation and a termination for the roof membrane.
• PIB Roofing MembraneSingle-ply membrane made from polyisobutylene, usually fleece-backed with a welding edge, long used in Germany and compatible with bitumen.
• PMMA Liquid RoofingFast-curing two-part polymethyl methacrylate resin, reinforced with polyester fleece, used for flat roofs, flashing details, balconies and walkways.
• Polyiso (Polyisocyanurate) Roof InsulationRigid thermoset foam board with facers, the most common low-slope roof insulation in North America, valued for high thermal resistance per thickness.
• Ponding WaterWater that stays on a low-slope roof after rain, commonly defined as water remaining 48 hours after the rain stops.
• Positive Drainage and Roof FallsThe design principle that a low-slope roof must have enough built-in slope (fall) to shed water within a set time, allowing for deflection and tolerances.
• Protected Membrane Roof (Inverted Roof)A low-slope roof in which the insulation is placed above the waterproofing, protecting it, and is held down by ballast or paving.
• PVC RoofingPolyvinyl chloride single-ply membrane made flexible with plasticisers and joined by hot-air welding; the first single-ply type standardised in the US.
• Reinforced Bitumen Membrane (RBM)The UK and European term for factory-made bitumen roofing sheets with polyester or glass reinforcement, laid in multi-layer systems on flat roofs.
• Roof Coating and RestorationA fluid-applied layer, such as acrylic, silicone or polyurethane, applied over a sound existing roof to waterproof it, reflect sunlight and extend its service life.
• Roof Deck (Low-Slope)The structural surface that supports a low-slope roof assembly, commonly steel, concrete, wood, poured gypsum or cementitious wood fibre.
• Roof Drain (Internal Drain)An outlet set into the field of a low-slope roof that collects rainwater and carries it down through pipes inside the building.
• Roof Walkway PadA protective pad or roll laid on a low-slope roof membrane to create a traffic path and prevent wear and puncture from foot traffic.
• Roofing Asphalt (BUR Asphalt Types)Oxidised asphalt graded by softening point (ASTM D312 Types I-IV) for mopping built-up and modified bitumen roofs at different slopes.
• SBS Modified BitumenModified bitumen membrane made elastic with styrene-butadiene-styrene rubber, installed by torch, hot asphalt, cold adhesive or self-adhesion.
• ScupperAn opening through a parapet or roof edge that lets water drain off a low-slope roof, either as the primary outlet or as an emergency overflow.
• Self-Adhered Roofing MembraneA roofing sheet supplied with factory-applied adhesive under a release film, bonded by peeling the film and pressing the sheet down.
• Silicone Roof CoatingA high-solids, UV-stable elastomeric coating used for low-slope roof restoration and SPF protection; many products tolerate ponding water.
• Single-Ply RoofingLow-slope roofing that uses one layer of factory-made polymer sheet, such as TPO, PVC, EPDM or PIB, joined at seams and held by ballast, fasteners or adhesive.
• Spray Polyurethane Foam (SPF) RoofingA seamless roof made by spraying two-part rigid polyurethane foam onto the substrate and covering it with an elastomeric coating or aggregate.
• Tapered InsulationRoof insulation boards cut with a built-in slope and laid in a planned sequence to create falls toward drains on a level deck.
• TPO RoofingThermoplastic polyolefin single-ply membrane, usually white and scrim-reinforced, joined by hot-air welding; the most widely used US low-slope membrane.
• Vapour Retarder (Vapour Control Layer)A layer placed on the warm side of roof insulation to limit water vapour moving from the building into the roof, where it could condense.
• XPS (Extruded Polystyrene) Roof InsulationClosed-cell polystyrene foam board made by extrusion, with low water absorption, used above the membrane in inverted and green roofs.