The short answer: yes, in most cases. Taking out a complete rooflight or roof window and fitting its equivalent counts as building work, so Building Control must be told and the new unit has to meet Part L. Fitting new glass to a sound frame is the exception. Sending that notice for a replacement is our job, not yours.
If you are weighing up replacing a rooflight (a skylight, in everyday speech) and wondering about Building Regulations, the answer depends on what exactly comes out. This page is part of our misted and failed rooflights guidance and deals only with that one question.
Replacing the whole unit
When the frame and the glazing come out together and a new unit goes in, the work is controlled. That is true even if the new rooflight is the same size, in the same place, on the same kerb. The regulations treat a new or replacement rooflight or roof window as a controlled fitting, so it must be notified and must meet the current energy standard.
It is easy to assume that like for like means exempt. It does not. The shortcut people have in mind is a narrower one, covered next.
The reasoning is simple. A rooflight is a hole in the thermal envelope of the building, and a replacement is a chance to bring that hole up to the current standard. It is also part of the weathering of the roof, so the way it meets the kerb or the tiles matters. Both points are checked when the work is notified.
Changing only the glass
If the frame is sound and only the glazing is swapped, the work is not a controlled fitting. Approved Document L says as much, at paragraph 10.6. The point is that nothing structural or weathering related changes, and the frame stays as it was.
In practice this narrow route is used less than people expect, because a misted unit often sits in a frame that has aged along with it. We look at the frame during the survey and tell you which route applies. The trade-offs are set out in replacing the glass or the whole rooflight.
What the new unit has to achieve
Part L sets thermal performance for replacement units in existing homes. The figure you must meet depends on what type of unit it is.
| Unit | Where it sits | Must meet |
|---|---|---|
| Roof window | Pitched roof | 1.4 W/m²K, or Window Energy Rating band B |
| Rooflight | Flat roof or lantern | 2.2 W/m²K |
Conservation rooflights, which sit in pitched roofs, follow the roof window figure. A lower number means less heat escapes, so a modern unit is usually a clear step up from the one it replaces. The fuller picture is in our Building Regulations guide, and the product side is in energy efficient rooflights.
Who deals with Building Control
You do not have to. We handle the notification where the work is notifiable. It can go through the local authority or through a registered building control approver, which is the current name for a private route. Either way, the point is that a record of the work exists and the unit is checked against the standard.
Brighton and Hove is a single city authority, so the council is the usual route for the city. Outside it, the district council runs Building Control, including inside the South Downs National Park, even though the park authority decides planning there.
What you receive afterwards
A notified job leaves a paper trail. When a buyer's solicitor later asks about the roof, you have evidence that the replacement was done to the standard of the day, rather than a verbal assurance from whoever fitted it. That matters most with a sale or a remortgage, when an unrecorded unit can hold things up. We keep the process tidy so you are not hunting for documents years afterwards.
Where planning fits
Building Regulations and planning are separate. A like for like replacement in the same opening rarely raises a planning question for a house, but flats, listed buildings and homes under an Article 4 direction can be different. If in doubt, ask the council, and read the planning guide for Brighton and Hove rooflights first.
If you live in a converted flat, your lease may also require the freeholder's written consent. That is a lease matter, not a regulations matter, and it is explained on our page for flats and leasehold buildings.
When the opening changes
Everything above assumes the new unit goes into the opening the old one left. If you want it bigger, or want a roof window where a fixed rooflight sat, that is a new opening in the roof. Then Building Control looks at the structure too: whether rafters or joists need trimming, how the opening is weathered, and what it means for fire and energy. The job moves from a swap to an alteration, and the survey is where we confirm which one you have.
It also changes the escape question in a loft room. A roof window is only accepted as an escape route where the storey sits roughly 4.5 m above the ground or lower, so a replacement does not automatically make a bedroom safe to sleep in. We will say so at the survey if that applies.
What this means for your quote
Because notification is part of the job, it is already inside the fixed written quote. The access plan also states the Building Control route in plain words, so nothing is left to chase. If you want the pricing side, see how much it costs to replace a misted rooflight.
When the work is complete, the installation carries our 10-year workmanship guarantee. To have your own roof assessed, book the free survey, or go back to the misted and failed rooflights hub.
