Rooflight

A raised frame or upstand constructed on a roof to support and weather items such as rooflights, smoke vents and plant, lifting them above the waterproofing plane. The membrane is dressed up the kerb and the unit itself or a flashing caps the top edge.

Any element that passes through the roof waterproofing, such as soil vent pipes, flues, cables, plant supports and drainage outlets. Each penetration must be individually sealed, typically with upstands, sleeves, preformed collars or liquid-applied detailing, and penetrations are a leading location for leaks.

The vertical or near-vertical continuation of the roof waterproofing above the general roof level at abutments, parapets, rooflight kerbs and penetrations. UK guidance calls for upstands of sufficient height above the finished roof surface, terminated with a flashing or capping so water cannot get behind the membrane.

A measure of thermal transmittance, the rate of heat flow through unit area of a building element per unit temperature difference between inside and outside, expressed in watts per square metre kelvin. Lower U-values indicate better insulation, and limiting values for roofs and other elements are set by national building regulations.