A flat rooflight is normally installed onto a prepared, weathered upstand rather than directly onto the roof deck. The kerb must provide a level, adequately supported fixing surface while maintaining insulation continuity, drainage and the required height above the finished roof.
What the upstand needs to achieve
The upstand transfers the rooflight loads into the building structure and creates the raised perimeter needed for reliable weathering. Its width, construction and fixing substrate must suit the selected rooflight frame.
An insulated timber kerb is common on residential projects. Concrete, steel or other project-specific supports may be required for larger or heavier units.
Typical coordination points
Confirm whether dimensions are structural opening, inside kerb, outside kerb or overall rooflight size. These are not interchangeable.
The roofing membrane should be dressed up the kerb and terminated to suit the approved frame detail. Build a positive fall into the kerb or roof so water does not remain against the glazing.
Before ordering, follow our rooflight measuring guide to label the internal opening and external upstand dimensions correctly.
Project checklist
Typical details are guidance only. The architect, roofer, structural engineer and rooflight supplier must coordinate the final kerb and waterproofing arrangement.
Bespoke rooflight specification, project coordination and installation across London and the UK.