A continuous rooflight is an elongated daylight structure in a roof: a framework of aluminium or steel with glass or plastic infills that brings light into the space below over a considerable length. Where a dome rooflight lights one point, a continuous rooflight lights a strip or a whole room.
You find them over industrial halls, shops, open-plan offices, atria, corridors and swimming pools — and in houses over an extension, a kitchen or a stairwell.
Forms
- Mono-pitch: a single sloping plane, often abutting a taller wall.
- Ridge form: two sloping planes with a ridge in the middle. The classic factory rooflight.
- Barrel form: a curved section, usually in plastic or curved glass.
- Pyramid or lantern form: four sloping planes, often over a square room.
- Sawtooth (north light) roof: a series of north-facing rooflights, giving plenty of light without direct sun. Still an excellent solution for workspaces.
A flat, horizontal version is not advised: water stands on it, dirt sticks, and the soiling is visible from inside. Always give a rooflight some pitch.
Build-up
- The kerb. An insulated upstand on which the rooflight sits and up which the roof covering is dressed. Adequate height is essential to hold back ponding water and snow.
- The profile system. Aluminium or steel, thermally broken. A non-broken profile is a thermal bridge that produces plenty of condensation in winter.
- The infill. Insulating glass (clear, solar control or laminated) or plastic multiwall sheet. Glass is clearer and more durable, plastic lighter and cheaper.
- The condensation channel. Well-designed systems have a channel within the profiles that collects condensation and any incidental water and drains it outside. This component is often forgotten, and is then the source of “unexplained” drips.
Design points
- Overheating is the real risk. A horizontal or shallow-pitched roof plane receives more solar energy per square metre in summer than a facade does. A south-facing rooflight without solar control glass or external shading makes the space below unusable in July.
- Ventilation or smoke vents. Opening sections shed heat; in buildings with a smoke and heat exhaust requirement, sections are built as SHEV vents.
- Safety. Plastic and ordinary glass in a roof are not walkable. Where people go onto the roof: fall protection, or laminated glass assessed as non-fragile.
- Maintenance and cleaning. Think before construction about how anyone will get there: anchor points, a walkway, a standing place for a platform. Without cleaning, light output falls year on year.
- Leaf clearance. Where a rooflight meets a taller wall or sits between roof planes, a gutter forms and fills with leaves. Plan the inspection.
- Consent. A rooflight is an alteration to the roof; on a listed building, in a conservation area or in a block of flats, extra requirements may apply.
Related terms
- Dome rooflight
- Light hood
- Rooflight kerb
- Clerestory
- Flat roof
- Daylight factor
- Light transmission
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.