Roofer fitting a new roof window into a tiled pitch with the flashing kit visible

Skylights and roof windows, fitted properly

New roof windows and replacements installed by vetted local roofers, with the flashing done right so they never leak.

Quick answer: a new roof window costs £900 – £1,600 each supplied and fitted in 2026, including the flashing kit and internal finishing on a straightforward pitched roof installation. The flashing is what decides whether it stays watertight, which is why this is a roofer's job, not just a glazier's.

Skylight and roof window installation covers new openings cut into a pitched roof, like-for-like replacements of tired old units, and re-flashing windows that have started to leak. Done well, a roof window is the cheapest transformation in the house: lofts, landings and dark kitchens get more daylight from one roof window than from a much larger vertical window, because light arrives from above all day.

Flashing kits done right = no leaks

Nearly every "leaking skylight" we hear about is a flashing failure, not a window failure. Each window is sealed to the roof by a flashing kit matched to the covering: one profile for slate, another for profiled tiles, others for plain tiles and flat roofs. The kit has to be the right one, the tiles or slates have to be cut and dressed around it correctly, and the underfelt has to be detailed to shed water past the opening. Where sealant appears instead of flashing, a leak is booked in advance. This is exactly the same discipline as good pitched roofing, which is why we match roof window jobs to roofers rather than window fitters.

What we arrange

New roof windows: the opening cut, trimmers fitted, window and flashing kit installed, and the reveal lined and plastered inside.
Replacements: swapping failed or fogged units, often reusing the opening within a day.
Re-flashing: renewing the kit and surrounding tiles on a leaking but otherwise sound window.
Windows during a re-roof: the cheapest moment to add them, while the covering is already off.

Glazing and blind options

Standard double glazing suits most rooms, with upgrades worth considering case by case: acoustic laminated glass under flight paths or busy roads, solar-control coatings on south-facing pitches to stop summer overheating, triple glazing in cold exposed spots, and easy-clean coatings where access is hard. Blinds run from simple blackout to solar-powered remote-controlled versions; factory-fitted blinds are neater and seal better than retrofitted ones, so decide before installation day.

Building regs note: roof windows rarely need planning permission, but building regulations do apply: the structural opening, the glazing specification, and escape-window requirements if the loft is a bedroom. A competent installer designs to the regs from the start; our building regulations guide explains who signs what off.

What it costs

The working figure is £900 – £1,600 per new roof window, supplied and fitted. Position on the roof, the covering, access and the internal lining work decide where in the range a job falls, and multiple windows fitted on the same visit cost less each than separate visits. You can include roof windows as an extra in our roof cost calculator to see them alongside a wider roofing job, or get itemised quotes for the windows alone.

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Roof window FAQs

Skylight and roof window questions, answered

A new roof window costs £900 to £1,600 each supplied and fitted in 2026, including the flashing kit and internal finishing on a straightforward pitched roof installation. Where the window position falls, the roof covering, and the internal lining work move a job within that range. Try the roof cost calculator to price windows alongside other roof work.

Almost always because of the flashing, not the window. Every roof window is sealed to the roof by a flashing kit matched to the covering: one profile for slate, another for profiled tiles. Leaks come from the wrong kit, tiles not dressed correctly around it, or sealant used where flashing should be. A window fitted with the correct kit by a roofer who works with them routinely should simply not leak.

Usually not: roof windows generally fall under permitted development provided they do not protrude more than 150mm above the roof plane, with tighter rules in conservation areas and on listed buildings. Building regulations do apply, covering the glazing specification, escape requirements in loft rooms and the structural opening. See the building regulations guide.

Sometimes. Many roof windows are fitted largely from inside the loft, and where the position is close to the eaves a roofer may work safely from a tower or secured ladder. Higher positions, fragile coverings or replacement of the surrounding tiles can still need scaffold or an access tower, which is priced per job.

Standard double glazing suits most rooms, with upgrades for noise reduction, extra thermal performance, solar control to stop a south-facing loft overheating, and easy-clean coatings. Blinds range from basic blackout to solar-powered and remote-controlled versions, and factory-fitted blinds are usually neater and better sealed than retrofits.