Size and type of rooflight
The first thing that sets the figure is the rooflight itself. A small fixed dome over a landing and a large pyramid or lantern over a kitchen are different pieces of kit, with different amounts of glass, frame and labour. Bigger units are heavier, need more hands on the roof, and cost more to make.
The type matters as much as the size. A fixed rooflight is simpler than one that opens, and a flat rooflight in a single sheet is simpler than a multi-part glass roof. Shape plays in too: a standard rectangle can be made from stock sections, while a curved, angled or very large unit is made to order and takes longer to build and fit.
A framed skylight in a pitched roof is a different job again from a unit on a flat roof. The pitched one sits within tiles or slates and needs flashing worked into the roof covering. The flat one sits on a kerb and meets a waterproof membrane. Neither is harder in every case, but they are not the same job, and the quote reflects that.
Glass only, or the whole rooflight
If the frame is sound and only the sealed unit has misted, swapping just the glass is a smaller job. It leaves the roof covering alone and needs less time. If the frame has aged, or the rooflight is a moulded plastic dome, the whole unit comes out. That brings in the kerb, the flashings and the finish round the opening. The line between the two jobs is drawn on the glass-only page.
Which job you need is settled at the survey, and the choice sets the biggest step in the figure. We would rather tell you plainly which one your rooflight is than quote for the larger job by default.
The kerb and the roof around it
The kerb is the short raised frame that a flat-roof rooflight sits on. It carries the weight, lifts the glass clear of standing water and gives the waterproofing something to turn up against. Often the old kerb is sound and the new unit is built to fit it. Sometimes it has soft timber, a cracked section or a height that no longer suits the roof covering, and then it is rebuilt or replaced along with the rooflight.
The roof covering matters too. A new rooflight has to be weathered into whatever surrounds it. On a pitched roof, that means the tiles, slates and flashings next to the opening. On a flat roof, it means the membrane or felt. If those are in good order, the work is tidier. If they have to be opened up and re-dressed to make a watertight joint, that is more time and materials. We look at these at the survey, from the roof where it is safe to do so, and list them in the written quote.
The glass specification
Glass is not one thing. A plain double-glazed unit is the starting point. From there, each addition changes what the unit does and what it takes to make.
- Low-emissivity coating and gas fill hold more heat in the room.
- Solar control coating reduces the heat the glass lets through, which matters on a skylight facing the sun.
- Laminated glass holds together if it breaks, and suits a rooflight over a stair, a landing or a bed.
- Self-cleaning or tinted finishes suit specific positions.
- Triple glazing adds a third pane where the frame is deep enough to take it.
New rooflights in existing homes have to meet a heat-loss standard. For rooflights the figure in the current Part L rules is 2.2 W/m²K. A better specification beats that comfortably. The rule is set out in full in the planning and Building Regulations guide.
Access, finishing and opening gear
How we reach the rooflight shapes the labour. A ground-floor extension roof reached from a short ladder is simple. A rooflight three storeys up, over a lightwell, or behind a ridge may call for scaffold or a tower, and scaffold is a cost in its own right. A roof that has to be crossed carefully, because the surface will not take a person, adds care and time. We note the access route at the survey.
Inside the house, the job may not end when the glass is in. A new rooflight sometimes means a new plastered or boarded splay or lining round the opening, filling and decorating the reveal, or making good a ceiling that the old unit had stained. Say at the survey whether you want us to finish the room to paint stage or hand over a clean, ready-to-decorate opening. Each is quoted as stated.
Opening gear is the last variable. A rooflight that opens by hand, with a pole or a lever, is simpler than one with an electric motor, a rain sensor and a wall control. The motor and the wiring are separate items in the quote. What that involves is covered under electric opening rooflights.
Why this page gives no figure
Every figure for a rooflight job comes from the points above, and two jobs that look alike from the garden can end up in different places on every one of them. A number on a web page would be a guess, so there isn't one here. Quoting from a photo has the same problem.
The route we take is simple. A free survey comes first, where we measure the opening, look over the frame, the kerb and the roof around it, note the access and agree the glass and finish with you. After that you get a written quote with a fixed figure, which does not change as the work goes on. If Building Control needs telling about the job, we do that for you, and the workmanship is covered by our ten-year guarantee.
The wider picture of what a skylight figure is made of is on our costs page. When you are ready, ask for the survey, or send photos and measurements on WhatsApp. The full process for this kind of job is set out on replacing misted rooflights.