Who fits roof windows
Do roofers put in Velux windows?
The short answer
Yes. Fitting a roof window is roofing work. The opening is cut through the covering and the rafters, the frame is fixed into the slope, and the flashing is dressed to the tiles or slates so rain runs over it. A roofer does that part, while a carpenter or builder may add the trimming inside. Velux is the best-known name, but the same job applies to any make of roof window.
Why a roofer is the sensible trade for a roof window, what the job involves from slope to ceiling, and the rules that apply.
Why the opening is a roofing job
A roof window is not a window that happens to sit in a roof. It is part of the weatherproofing. The frame is set flush with the slope, and rain has to run over its flashing and down onto the covering below, exactly as it runs over the tiles themselves. If any part of that detail is wrong, the water will find the gap, and the evidence turns up later as a stain on the ceiling beside the glass.
The work begins on the outside, from scaffold or a safe working platform. The covering around the opening is stripped back, battens are cut, and the rafters are trimmed or doubled up to make room, which is structural work. The frame goes in, the flashing is dressed to suit the tile or slate profile, and the covering is relaid around it.
That sequence is why the job sits with a roofer. A window fitter without roofing skills can set the glass but cannot make the slope watertight around it.
What a roofer does and what other trades add
The roofer's share is the opening, the structure around it, the frame, the flashing kit and the weathering. Many roof windows are supplied with a flashing kit matched to the covering, which is dressed to tiles, slates or flat profiles, and choosing the right kit is part of the job. Our answer on Velux flashing kits explains how that works.
Inside the house, the lining of the opening, the plaster finish and decoration are carried out by a plasterer, carpenter or decorator, or by the owner. In a loft conversion there is often a builder in charge, with the roofer brought in for the slope. We can work alongside a builder, or deal with the whole of a single window ourselves where it is a simple like-for-like replacement.
Where you are changing an existing window, the old frame and flashing are removed and the new ones fitted in the same opening, which is quicker than a new hole. Even then the surrounding covering has to be lifted and relaid, because an old flashing is tucked in under the tiles around it.
Rules that apply: thermal performance and structure
Under Approved Document L (2021 edition, Table 4.2), a roof window in an existing home must reach 1.4, or Window Energy Rating Band B. A rooflight, meaning a unit that stands up from the roof on a kerb, is held to 2.2. From 24 March 2027 the 2026 edition takes over, and its Table 3.2 gives the same values. Which of the two you are fitting decides the figure that applies.
Cutting the rafters is a structural alteration. The Planning Portal lists that among the reasons to apply to building control, so your roofer should tell you whether a particular opening is notifiable. Where it is, we handle the notification, so the inspector is aware before the opening is made.
Our guide to roof window Building Regulations goes through the thresholds in detail.
Planning and the side-slope glazing rule
Roof windows on an unlisted house often fall within permitted development, with limits. The window may stand no more than 0.15 metres proud of the roof surface, and nothing may climb higher than the ridge. If the slope faces the side of the house, the glass must be obscured, and it must not open unless the opening part sits over 1.7 metres up from the floor. The obscuring is required whatever the height.
Listed buildings need listed building consent, and an Article 4 direction can take the rights away, and flats do not enjoy the same rights because the permitted development rules apply to dwellinghouses. A conservation area does not remove roof window rights in itself, but a direction can.
Our guide to skylight planning permission sets out each case and which council to ask, because the South Downs National Park has its own planning authority.
Questions worth asking first
A few questions separate a considered quote from a vague one. Which window model and size is being fitted, and which flashing kit goes with your roof covering? Is the structure around the opening included, and will an inspector need to be told? Who finishes the inside, and when, and is that tied to the roofing dates? Who clears the old covering and debris away when it is over?
The quote should name the window and the glazing, so you can check it meets the Part L figure. A quote given after a survey means the roofer has seen the pitch, the covering and the loft, and it comes as one total.
Also ask how long the roof will be open. A careful roofer makes a new opening weathertight before leaving each evening, and the weather forecast is part of the planning. The main skylights and roof windows page covers the range of options.
Related questions
Roof window fitting questions
Can I fit the window myself and just hire a roofer for the flashing?
In theory, but it splits responsibility for a watertight result between two people. If it leaks, each can point at the other. Most roofers prefer to fit the frame and flashing as one operation, and they may not take on a window they did not fit.
Does the make of roof window change the fitting?
Yes, in the details. Frames, flashing kits and fixing methods differ between makers, and each maker publishes instructions for its own range. The principle of a cut opening, a fixed frame and a dressed flashing is the same whatever the label.