The short answer
Typical UK market figures for a fixed flat rooflight, supplied and fitted, run from £1,000 to £2,800. Treat it as a starting point only, and not as our prices. Where a particular job lands depends on six things: size, whether the unit opens, the glazing specification, the kerb, how the unit ties into the roof covering, and access to the roof. A written quote follows the free survey, so the figure you are given is for your roof.
What the market range stands for
The range above is a broad market figure for a fixed unit, and a starting point only. Opening units sit higher, and the full set of ranges is on the costs page, which also explains how a written quote is built. A flat rooflight can fall inside that range or outside it on an awkward roof.
The spread is wide because two flat rooflights that look alike from the garden can be very different jobs. The sections below take the drivers one at a time so you can see where your own roof is likely to sit.
The figures also assume a straightforward flat roof in sound condition. Anything that adds structural work, such as a wider opening that cuts several joists, sits outside a simple range and is priced once the survey has shown what is involved.
Size and shape of the unit
Larger glass costs more, in the unit and in the handling. A bigger pane is heavier, needs extra hands or a lift to place, and needs a stronger frame. Very large or unusual sizes are made to order, which stretches the delivery time as well as the figure.
The number of units matters too. A row of three on an extension, like those shown on the flat roof rooflight installation page, shares access and set-up between them, which changes the sum compared with one unit on its own.
Shape counts as well as area. Plain rectangles are the easiest shape for a maker to produce, while a square pane, a long narrow strip or a unit with a custom kerb height can be more involved. Standard sizes from the manufacturers usually cost less than made-to-measure ones, so where the opening can be set to suit a standard unit, that is worth raising at the survey.
Fixed or opening
A fixed unit is glass in a frame. An opening unit adds hinges, a motor or a hand mechanism, and often a rain sensor and wall controls. That extra pays for a function, such as airing a room or reaching the roof, and not only for a finish.
An electric unit also needs wiring, which means an electrician's time. We record that in the plan, since it affects both the figure and the order of work on the day.
If you are unsure whether you need an opening unit, ask what it is for. A rooflight over a landing that is simply meant to brighten the space rarely needs to open. One over a kitchen, a bathroom or a flat-roof access point is more likely to earn its extra cost. Saying so at the survey lets us price both options in one quote.
- Fixed unit: glass and frame only
- Manual opening: adds the mechanism
- Electric opening: adds actuator, controls and wiring
- Rain sensor: a common extra on opening units
Glazing specification
The glass is a large part of the price. Double or triple glazing, a laminated inner pane, a solar control coating, self-cleaning glass and an anti-slip finish each add to the unit. The finished unit also has to meet the current thermal limit for a rooflight, and the figures for it are in the Building Regulations guide for rooflights.
Glass also affects running comfort. A better specification costs more on the day and tends to pay back in a room that is easier to live in, so it is worth deciding deliberately and not by default. We name the glazing in the plan, so you can compare like with like when you hold two quotes side by side.
The sensible approach is to specify what the room needs. A west-facing kitchen that takes strong afternoon sun asks for different glass from a hallway.
Kerb, covering tie-in and access
On an existing flat roof the rooflight stands on a kerb or upstand, and either may need building or adapting. The covering then has to be joined around it, and the state of the old felt, EPDM or GRP decides how much work that is. If the covering is worn, renewing it in the same visit may be the better plan.
Access comes last. A low single-storey roof reached from the garden is quicker to work on than a first-floor roof that needs scaffold, or a crane for the glass. A roof with a parapet, a terrace or a restricted street takes longer to prepare.
| Driver | What it changes |
|---|---|
| Size | Glass, frame and handling |
| Fixed or opening | Mechanism, controls and wiring |
| Glazing | Coatings, panes and finish |
| Kerb | Building or adapting the upstand |
| Covering tie-in | Joining the new unit to the existing roof |
| Access | Scaffold, lifting and set-up time |
How you get a figure for your roof
A real figure comes from a survey. We visit free of charge, measure the opening and the roof, assess the covering, and put the quote on paper, with a plan that names the unit and its size and sets out the council position for your address. It also lists how Building Control will be told, how long the unit takes to arrive and which day we fit it. A ten-year guarantee on our workmanship is issued with the job, on paper.
That order matters. A price given before anyone has looked at the roof is a guess, and a guess can change the moment the covering is lifted. A quote written after the survey already has the covering, the joists and the access in it, so the number you are given is much less likely to move.
It also helps to have the quote itemised. Ask for the unit, the kerb work, the covering tie-in, the access and the finishing inside to be shown as separate lines. You then see which of the six drivers is doing the work on your roof, and you can decide whether a different specification or a different time of year would change the figure.
If you are weighing flat units against a glazed lantern, the roof lantern cost answer runs through the same drivers for that shape, and the garage roof rooflight answer covers one common flat-roof case.