What are flat rooflights?
Across Greater London, our flat rooflights work covers fixed double or triple glazed rooflights for flat roofs and extensions. Survey first, fixed price second, fitting third.
Mansard and loft conversions are common across London, and roof windows are often set out alongside dormers on the rear slope. Party walls are a fact of life in London terraces, and rooflights close to a shared wall need detailing that keeps the neighbour's side dry too.
Towns in Greater London
What you can choose
- Integral or fitted blinds
- Rain sensor if paired with an opening unit
- Square, rectangular or long-format sizes
- Plastered or lined internal reveal
- Frame colours: anthracite, black, white or RAL
- Even, top-down daylight across the whole room
- Inner pane laminated for safety overhead
Planning and building rules in England
In England a rooflight on a house is usually permitted development under Class C if it projects no more than 150 mm beyond the roof slope and sits no higher than the ridge. A rooflight on a side-facing slope must be obscure-glazed, and fixed shut unless the opening part is more than 1.7 m above the floor.
Building Regulations Approved Document L sets a limiting U-value of 2.2 W/m²K for new or replacement rooflights in existing homes, measured in the horizontal plane; roof windows need 1.4 W/m²K or a Band B energy rating. The Future Homes and Buildings Standards, published in March 2026, apply from 24 March 2027 and keep the 2.2 W/m²K limit for rooflights.
Guide prices
Guide prices for flat rooflights in Greater London are the same as anywhere we work — what changes the price is the job: access, structure, scaffold and finishing.
| Option | Guide price inc VAT | Ex VAT |
|---|---|---|
| Large or triple glazed (1500 × 2500 mm and up) | £2,395 – £4,195 | £1,995 – £3,495 |
| Mid-size double glazed (1000 × 2000 mm) Typical | £1,675 – £2,395 | £1,395 – £1,995 |
| Small double glazed (up to 1000 × 1000 mm) | £1,195 – £1,795 | £995 – £1,495 |
How the job runs
- Tell us about the roof. Send the postcode, rough sizes and a photo or two through the form, WhatsApp or the guide-price tool.
- Free survey. For new installations a surveyor measures the opening, checks the roof build-up and talks through glass and options.
- Fixed written quote. You get the product, the work and the price in writing. Nothing is ordered or paid for until you agree.
- Fitting and handover. We fit, seal and make good, then hand over product data, warranties and any certificate paperwork.
Flat rooflights in nearby areas
Common questions
Do flat rooflights leak?
A well-fitted flat rooflight should not leak. Leaks almost always come from the upstand or membrane detailing, not the glass unit, which is why the upstand height and the way the roof covering is dressed up and under the frame matter more than the brand.
Double or triple glazing?
Double glazing suits most domestic jobs. Triple glazing improves thermal performance and cuts noise from rain, which is worth it over bedrooms or where the energy calculation is tight.
Can you fit into my existing flat roof?
Yes. We form a new opening, trim the joists, build and waterproof an upstand and make good the ceiling. A survey confirms the joist direction and roof build-up first.
How long does it take?
Fitting into a prepared upstand usually takes a day. Forming a new opening in an existing roof, including making good inside, is often two to three days.
Will I need planning permission in Greater London?
English householder permitted development (Class C) normally covers rooflights that stand no more than 0.15 m proud of the roof plane and stay below the highest part of the roof.
