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Low-Slope Roofing Materials
Roofing material categories suited to low-slope roofs.
APP Modified Bitumen
A modified-bitumen membrane in which the asphalt is modified with atactic polypropylene (APP), giving a plastic-like, heat- and UV-resistant sheet typically torch-applied. Distinct from SBS modified bitumen, which uses a rubber-like elastomeric modifier better suited to cold-flex applications.
Built-Up Roof (BUR)
A traditional low-slope system of alternating layers (plies) of bitumen and reinforcing felts, typically topped with gravel or a cap sheet. The original redundant membrane roof.
EPDM Membrane
A single-ply synthetic rubber membrane for low-slope roofs, valued for its long field track record and flexibility. Commonly black; ballasted, mechanically attached, or fully adhered.
Green (Vegetated) Roof
A low-slope roof assembly in which a waterproofing membrane is overlaid with drainage, growing medium, and living vegetation. Classified as extensive (shallow, low-maintenance) or intensive (deep, garden-like). The roofing family is defined by the single-ply or modified-bitumen membrane beneath the planting.
Liquid-Applied Membrane
A cold-applied liquid roofing and waterproofing membrane, most commonly a rapid-setting polymethyl methacrylate (PMMA) resin applied with a polyester fleece reinforcement to form a monolithic, self-flashing, self-adhering reinforced membrane with no seams or mechanical fasteners. Rapid-curing systems allow same-day installation, and the cured resin is UV stable. Used on commercial low-slope roofs and detail-heavy areas such as penetrations, balconies, and podium decks where sheet membranes are hard to flash.
Modified Bitumen
Asphalt-based low-slope membrane reinforced and modified with polymers (SBS or APP), installed in rolls by torch, hot mop, cold adhesive, or self-adhered.
PVC Membrane
A single-ply thermoplastic polyvinyl chloride membrane with hot-air-welded seams for low-slope roofs. Distinguished from TPO by its plasticizer chemistry and strong resistance to chemicals, grease, and fire.
Spray Polyurethane Foam (SPF) Roof
A seamless, fully adhered low-slope roof system created by spray-applying polyurethane foam directly to the deck, then protecting it with an elastomeric topcoat (acrylic, butyl, silicone, polyurethane, or polyurea). The foam provides insulation and slope-to-drain in the same application; the topcoat is the wearing surface and is re-applied every 10 to 20 years to renew the system. SPF assemblies are evaluated for hail under FM 4470 (moderate-hail and severe-hail ratings).
TPO Membrane
A single-ply thermoplastic polyolefin membrane with heat-welded seams, widely used on low-slope commercial roofs. Typically white and highly reflective (cool roof).