Flat Glass Rooflight in a Kingston Extension

Finished long flat glass rooflight in a new rear extension ceiling, with blue sky above and garden doors below

Where: Kingston upon Thames
The job: Rooflight for a new rear extension
Fitted: 1 long flat glass rooflight
Roof: Flat

A homeowner in Kingston asked us to add more natural light to a newly built rear extension. The answer was a long, narrow flat glass rooflight set into the strip of flat roof alongside the neighbouring wall, carrying daylight into the part of the room furthest from the garden doors.

Forming the opening

The extension was already structurally complete, with painted steel beams spanning the room and the ceiling boarded out. We formed the rooflight opening in the strip of roof between the steels, trimming it in timber so the kerb would sit square and true. At this stage it was still open to the sky, looking straight out onto the scaffold and the neighbouring brickwork.

Rooflight opening formed in the extension ceiling between red painted steel beams, open to the sky — The opening formed between the painted steels, still open to the sky.

View from inside the extension up through the open rooflight opening to the scaffolding above — Looking up through the opening to the scaffold, with the garden doors below.

Setting the glass

The glass unit was lifted into position from the scaffold, bedded onto the kerb, then sealed and dressed in. Because the rooflight sits in a tight gap between the new extension roof and the older wall beside it, the detailing around its edge mattered as much as the glass itself: the upstand and the roof covering have to meet cleanly to keep the junction watertight.

Newly installed flat glass rooflight seen from roof level, in the narrow gap beside the neighbouring brick wall — The glass in place, seen from roof level beside the neighbouring wall.

Flat glass rooflight on the extension roof, viewed along its length from the scaffold — Viewed along its length, with the roof covering dressed up to the kerb.

The finished result inside

From inside, the rooflight reads as a clean slot of sky in the ceiling. The reveals were boarded and taped ready for plaster, and the daylight now reaches back over the kitchen.

Glazed rooflight seen from inside the extension with the kitchen below and daylight filling the room — Daylight reaching back over the kitchen.

Finished flat glass rooflight in the extension ceiling with blue sky above and garden doors below — The finished rooflight, with sky overhead and the garden doors at the far end.

If your extension is darker in the middle than it should be, a rooflight is usually the simplest fix. See our flat glass skylights and roof lanterns.

Questions about this job

Why fit a long, narrow rooflight rather than a square one?

A long rooflight that runs back towards the original house pulls daylight into the deepest part of the room, which is usually the darkest. On this Kingston extension the glass sits in the strip of flat roof beside the neighbouring wall, so it lights the middle of the room without competing with the garden doors at the far end.

Can a rooflight be fitted between structural steels?

Yes. The opening is planned around the steelwork so the kerb sits neatly between the beams. Here the painted steels were already in place, and the opening was formed and trimmed in timber between them before the glass went on top.

Do flat glass rooflights need a kerb?

Almost always. A flat glass rooflight sits on an upstand, or kerb, built above the roof deck. The kerb lifts the glass clear of standing water and gives the roof covering something to dress up against, which is what keeps the detail watertight over the long term.