Do Roofers Install Velux Windows?

A roof window sits level with the covering, as part of the slope. Velux is the best-known maker, and its name is often used for any roof window. The glass is the easy part. What keeps the rain out is the way the frame is joined to the roof around it.

What part of the job is the roofer's?

First the covering is removed around the opening, the underlay is cut and one or more rafters, the sloping timbers, may be trimmed and a timber frame built to carry the load. The window frame is fixed, then the flashing kit goes round it. The kit is a set of pre-formed pieces that lap over the covering at the sides and under it at the top, so water runs over the joints. The slates or tiles are then cut and refixed to the flashing, and the underlay is lapped to the frame.

A plasterer or carpenter then forms the lining inside the opening. A roofer can do that too, or a builder can, so ask which is included in the price.

Fitting a roof window well depends on a few details, and the questions are practical ones.

Which questions should I ask?

Ask which flashing kit will be used and whether it suits your covering, since slate, plain tile and profiled tile each need a matched kit. Ask whether the work includes the inside lining, plastering and decoration. Ask what will cover the opening if the weather changes before the day ends, since a hole in a roof cannot be left open. Ask what happens to the rubbish and who arranges any scaffold or tower.

If the window is replacing an existing one, ask whether the old flashings and the opening can be reused. Our guide on replacing a Velux in the same opening explains what makes that simpler. If it is a new opening, our guide to fitting a new roof window goes through the steps.

Our routine is a survey first, pictures of your own slope next and a single written price after.

A roof window is not a thermal element in law, but Approved Document L still sets its standard. In the 2021 edition, Table 4.2 sets roof windows at 1.4, or Band B at minimum on the Window Energy Rating scale, through a note to the window row. Rooflights have a different figure, 2.2. Do not mix the two up.

Does fitting a roof window need planning permission or building control?

Class C of the permitted development order covers roof alterations on a dwellinghouse, and a roof window is normally within it if it does not protrude more than 0.15 metres beyond the plane of the roof slope. On a side-facing slope the glass must be obscure, and it must not open unless the part that opens lies over 1.7 metres up from the floor inside. A conservation area or listed building adds its own checks, so ask Somerset Council's planning team. Flats are not dwellinghouses, so Class C does not apply to them.

On Building Regulations, a new opening cuts a rafter, so check the structure, and your building control body can confirm whether an application is needed. Somerset Building Control is on 0300 303 7790. Our guide to roof windows and skylights covers more.

For typical UK figures, MyJobQuote lists £1,100 for a standard mid-range Velux and around £100 less for a straightforward swap (Sep 2026). What moves the price on your roof is the size of the window, the flashing kit, whether a rafter must be cut, scaffold or tower access, the roof covering and the interior finish.

Is a roofer always the right person?

For the roof side, usually yes. A roofer who also does the internal lining saves you co-ordinating two trades. Where the opening needs structural change, such as a wide window, a number of windows, or work to a loft conversion, a builder or an engineer may be needed for the structure, with the roofer doing the weatherproofing.

Check that any quote says what it includes: VAT, scaffold, the window itself, the flashing kit and the internal finish. Ask what the written terms are if the window turns out to leak, and keep the paperwork. To picture a fitting day, read our answer on the Velux installation day walks through it, and we are happy to send a photo and a note on your roof once the survey is done.