01The rule
Most rooflight work is covered, and it is not just paperwork
If you are putting a new rooflight in a roof, or replacing a whole one, the Building Regulations apply. Only a few small jobs sit outside them.
Building Regulations are the national standards for how a building is built and altered. They cover things like structure, fire safety and energy use, and they are separate from planning permission, which is about appearance and the local area. Doing one does not do the other. If you are wondering whether you need Building Regulations approval for a rooflight, the working answer is yes for a new opening and yes for replacing a whole unit. We cover planning in a separate guide, skylight planning permission in Essex.
So do rooflights need building regulations? Sometimes, and when they do, the process is called notification. Before the work starts, Building Control (the council's building control team or a registered building control approver) is told about the job, or a competent person scheme installer self-certifies it after completion. They may inspect, and when it is finished you receive a completion certificate. Keep that certificate with the house papers, because a buyer's solicitor can ask for it later. On notifiable jobs, Radiant Skylights sends the paperwork to Building Control, so you are not left chasing it.
| The job | Notifiable? | Why |
|---|---|---|
| New rooflight in an existing roof | Normally yes | Structural alteration plus thermal limits |
| Swapping the entire rooflight, frame and glass | Yes | A controlled fitting under Part L |
| Replacing only the sealed unit | No | The frame and opening are unchanged |
| Roof lantern on an extension | Part of the extension | Follows the building work around it |
02New openings
Why cutting a hole in a roof is a structural job
A new rooflight takes out part of the roof's frame, and the regulations want to see that the load has somewhere else to go.
A pitched roof is held up by rafters, the sloping timbers that run from the ridge down to the wall. A new roof window usually means cutting through one or more of them, then framing the opening with doubled timbers so the weight passes around it. On a flat roof the joists beneath get the same treatment. That is a structural alteration, and Building Control will want to know it has been designed and built properly.
The new opening also has to keep the roof thermally sound. It is a hole in the insulation, so the frame, the kerb or flashing and the lining all need to join up to the insulation around them. That is what we think about on every job, and the full approach is on our warm specification page. It is also why the work comes under the energy part of the regulations.
- Rafters or joists cut and trimmed with a properly framed opening
- Insulation continued around the frame, without a gap
- A vapour control layer joined at the lining
- Fire safety and escape routes unaffected by the new window
- Notification made before the opening is cut
03Replacing
Replacing an old rooflight: whole unit or just the glass
This is the case where the answer splits in two, and the split is worth understanding before you get quotes.
A rooflight is a frame holding a sealed unit, which is the pair or trio of glass panes sealed with a gas in between. If the glass has failed but the frame is sound, replacing just the sealed unit does not need notification. Take out the whole rooflight, frame and glass together, and Part L, the part about saving fuel and power, treats the new one as a controlled fitting. The new one must meet a limiting U-value of 2.2 W/m²K in an existing dwelling. A U-value measures how fast heat passes through, and lower is warmer. A good modern double glazed rooflight is far below that limit, so the rule is a floor, not our target.
We can talk you through which route suits yours in sealed unit or whole rooflight, and the notification question is in is replacing a sealed unit notifiable. What happens on the day is set out in replacing an old rooflight.
Sealed unit only
The existing frame stays. The glass is swapped for a new unit. No Building Control notification, and the frame must still be in good order.
Whole rooflight
Frame and glass both come out. A new unit meeting 2.2 W/m²K or better goes in, and Building Control is notified.
04Who deals with it
What happens with Building Control on our jobs
You should not have to learn the system, so here is what we do on a notifiable job and what you get at the end.
Fitting to current Building Regulations is how we work, and it begins at the survey. We tell you straight away whether your job is notifiable. If it is, we notify Building Control, and you will not be asked to fill in forms or contact the council yourself. We also keep the fitting team the same from start to finish and protect floors and furniture while we work.
- Free survey and written quote, with the notifiable question answered up front.
- We notify Building Control before work starts.
- The rooflight is fitted with the warm-edge glazing and insulation tied in.
- Any inspection is arranged, and the completion certificate comes to you after sign-off.
Does Building Control need to hear about my rooflight?
Do I need Building Regulations for a VELUX in a loft conversion?
Yes. A new roof window cuts the roof structure and sits in the thermal envelope, so the work is normally notifiable. A loft conversion needs notifying as a whole, and the rooflights are part of that. See our VELUX window installation page.
What U-value does a replacement rooflight need?
Replacing a whole rooflight in an existing home has to meet a limiting U-value of 2.2 W/m²K under Part L. Good modern units sit well below it. We explain the figures in rooflight U-values explained.
Is Building Regulations approval the same as planning permission?
No. They are two separate systems, and having one does not mean you have the other. Most rooflights on a house need no planning application, but the regulations still apply.
Does a flat roof lantern on an extension need its own approval?
If it forms part of a new extension, the lantern is covered by the extension's own Building Regulations and planning route. Our roof lantern installation page explains how we work alongside that.
