Scrim

A factory-manufactured polymeric waterproofing sheet, typically EPDM, TPO or PVC, installed in a single layer and joined at laps by welding, adhesive or tape. Single-ply systems may be mechanically fastened, fully adhered or ballasted, and are widely used on flat and low-pitched roofs.

A sheet waterproofing material comprising a polyester or glass fibre carrier coated with oxidised or polymer-modified bitumen, normally installed in two or more bonded layers on flat roofs. It is the modern UK term for what was traditionally called built-up felt roofing.

Fibre drawn from molten glass, the most widely used reinforcement for polymer composites. Different formulations, such as E-glass, E-CR glass, S-glass and AR glass, balance cost, strength, electrical performance and chemical resistance. It is the standard reinforcement in GRP laminates, including liquid applied GRP flat roofing systems.

The mass of a fabric, mat or fibre layer per unit area, normally quoted in grams per square metre. It is the primary way reinforcements are specified and, together with fibre volume fraction, determines the cured thickness of each ply.

Core sheet cut with a grid of slits or kerfs, often combined with a scrim backing, so that it can conform to curved mould surfaces. The cuts also act as channels for resin flow during infusion, although they increase resin uptake and therefore the finished weight of the panel.

Core material cut from balsa, a fast-growing tropical hardwood whose naturally cellular structure gives high compressive and shear strength for its weight. It is normally supplied as end-grain sheets or scrim-backed blocks, and as a renewable material it is often selected where sustainability is a factor.