Flat Roof Skylight Cost — Cheltenham Price Guide 2026

As an indicative 2026 UK guide, a flat-roof skylight typically costs between £1,200 and £4,000 or more supplied and fitted, depending on size, glazing and whether a new kerb is needed. The only accurate figure for your roof is a fixed written quote after a free survey.

Flat-roof skylights are a clean, modern way to bring light into extensions, kitchens and landings. Because they sit on a kerb and rely on good weatherproofing, the detail matters. Here is what to expect on price.

Flat roof skylight prices at a glance (2026 guide)

• Small (around 0.6m x 0.9m), fixed: £1,200–£1,800 supplied and fitted
• Medium (around 1m x 1m), fixed: £1,600–£2,600
• Large (around 1.5m x 1m), fixed: £2,400–£3,500
• Extra-large or premium glazing: £3,500–£4,000+
• Opening/electric version: add roughly £400–£900 over the fixed equivalent

These are indicative figures covering the rooflight, weatherproofing and our installation labour. They assume an existing or builder-formed kerb. A new insulated upstand, if required, is priced separately at survey.

What affects the cost of a flat roof skylight

Size of the glass

Larger panes cost more in both the unit and the handling. Big single panes also need careful lifting, which can affect labour.

The kerb or upstand

A flat-roof skylight must sit on a raised kerb to shed water. If your builder has formed one accurately, that keeps costs down. If not, we can supply and fit an insulated upstand, which adds to the total.

Fixed or opening

A fixed pane is the most economical. Manual or electric opening adds ventilation, but costs more and, for electric, may need a power supply nearby.

Glazing specification

Solar-control coatings tame heat gain on sunny roofs, while acoustic or triple glazing adds comfort. Each upgrade adds to the unit price. See our energy-efficient skylight page.

Roof covering and access

The existing flat-roof finish, whether felt, EPDM, GRP or single-ply, affects how we detail the weatherproofing, and awkward access can add to labour.

Cost in Cheltenham & the Cotswolds: it is all in the kerb

Flat-roof skylights are the product we fit most often on rear extensions across Cheltenham and the surrounding area, and locally the figure is decided more by the kerb and the roof covering than by anything else. On the new and recent extensions going up around Bishop’s Cleeve, Brockworth and the growing edges of Gloucester and Tewkesbury, builders increasingly form an accurate, insulated upstand as part of the warm-roof build, often finished in EPDM or single-ply. Where that is the case, our job is clean and the skylight lands toward the lower-to-middle of the range. The picture changes on older flat roofs — the felted garage conversions and 1960s–70s rear additions common on the established Cheltenham estates — where a tired felt covering and a missing or out-of-square kerb mean we supply and fit a new insulated upstand, and that adds to the total.

One genuinely local point worth flagging: Cheltenham and the Severn vale around Gloucester and Tewkesbury see real rainfall, and the river-valley setting means weatherproofing detail is not the place to economise. A correctly upstood, properly flashed flat-roof skylight is what keeps water out for the long term, and it is the part of the job we will never cut short.

Conservation areas and modern flat roofs

A flat-roof skylight on a single-storey rear extension is one of the least contentious things you can add, even within Cheltenham’s Regency conservation areas, precisely because it sits flat and out of sight from the street. On a listed building or where a flat roof is visible from a public vantage point, it is worth checking, and building control runs through Cheltenham Borough Council, Tewkesbury Borough Council, Cotswold District Council or Stroud District Council depending on where you are. We will flag the position at survey; consent is separate from our pricing.

Worked examples

Example 1 — kitchen extension. A 1m x 1m fixed rooflight on a builder-formed kerb, single-storey, good access. Indicative total around £1,700–£2,300.

Example 2 — large opening rooflight. A 1.5m x 1m electric-opening skylight with solar-control glass and a new insulated upstand. Indicative total around £3,600–£4,500.

Example 3 — older felt garage conversion. A 1m x 1m fixed rooflight on a 1970s rear addition near Charlton Kings, including a new insulated upstand to replace the tired felt detail. Indicative total around £2,400–£3,000, with the new kerb doing most of the extra.

These are guide figures only. The accurate price is the fixed written quote after survey.

Ways to keep the cost sensible

• Form the kerb during the build. An accurate builder-formed upstand avoids extra work later.
• Choose fixed where you do not need ventilation. A fixed pane costs less than an opening unit.
• Target glazing upgrades. Solar control pays off on sun-facing roofs; you may not need it everywhere.
• Plan access. Booking while other roof work is underway can share equipment costs.
• Do not skimp on weatherproofing. In the wetter Severn vale, the upstand and flashing are what protect your investment.

Why the quote matters more than the guide

Kerb, roof covering, glazing and access all shape the real price. We survey your flat roof for free, then issue a fixed written quote with no surprises, backed by our written guarantee on our workmanship.

See our flat-roof skylight installation page for the product detail, compare with our electric and opening skylight cost guide, or get a quote for your fixed price after a free survey.