Roof deck

The surface onto which a coating, membrane, adhesive or covering is applied. In roofing this may be the structural deck, insulation, screed or an existing waterproofing layer; substrate condition, priming and compatibility govern adhesion and long-term performance.

A roof construction in which the thermal insulation is placed above the structural deck, keeping the deck and supporting structure at close to internal temperature. A vapour control layer is normally installed on the warm side of the insulation to limit the risk of interstitial condensation.

Steel or aluminium sheet cold roll-formed into trapezoidal, sinusoidal or other profiles to provide spanning stiffness, used as roof and wall cladding and as structural decking. Sheets are typically metallic-coated steel with a factory-applied organic coating, fixed through to purlins or rails, or used as the skins of built-up and composite panel systems.

The suction force exerted on a roof by wind flowing over and around a building, greatest at perimeters and corners. Roof systems resist uplift through mechanical fastening, adhesion or ballast, with design loads derived from wind actions codes and system resistance established by testing.