The short answer
Two jobs fall under the Regulations: cutting a new opening through a roof, which is building work, and swapping the entire rooflight, frame and glass, which is a controlled fitting and so has to be notified. A new sealed glass unit alone sits outside the notification rules. When a job calls for notification, we make it to Building Control on your behalf.
Which jobs are notifiable
The rule follows what is being changed. A fresh opening in a roof alters the structure and the thermal envelope, which makes it building work. Swapping a whole rooflight for a new one counts as fitting a controlled fitting, so that is notifiable too. Swapping the sealed glass unit alone leaves the frame and the opening as they were, which keeps it outside the notification.
| Item | Notifiable | Not notifiable |
|---|---|---|
| New opening | Forming a fresh opening in the roof | Nothing in this row |
| Whole unit | Replacing frame and glass together | Nothing in this row |
| Glass only | Nothing in this row | Renewing the sealed glass unit while the frame stays sound |
| Larger opening | Enlarging an existing opening | Nothing in this row |
Our page on replacing a rooflight under the Building Regulations works through the like-for-like cases in more detail.
The Part L limits that apply
Part L of the Building Regulations, in its 2021 edition, sets thermal limits for new fittings in existing dwellings. In Table 4.2 the figure for rooflights is 2.2 W/m²K. Roof windows are held instead to the ordinary window standard, which is 1.4 W/m²K, though the alternative route is to reach Band B for window energy.
A rooflight and a roof window are different products under these rules. A roof window is the pitched-roof type that opens on a hinge or pivot and sits in the plane of the roof. A rooflight is the wider term and covers flat-roof lights, lanterns and similar units. The product we propose for your roof decides which limit it must meet, the maker's data states which class each unit falls in, and each option's figure is stated on the quote.
Our guide to rooflight U-values explains how those numbers compare between glass and frame choices.
Who handles the notification
Where a job is notifiable the notification reaches Building Control through us, and its fee is shown as a separate line on the quote. Your council can carry out the building control, or you can use a registered building control approver, which is the private route under that name since April 2024. We tell you which route is being used for your job.
The inspection or sign-off that follows is arranged around the fitting, and the completion paperwork comes to you so it can be kept with the house documents for a future sale.
What a new opening involves
A new opening is more than a hole and a unit. The rafters or joists that are cut need trimming members either side, the load has to be carried round the opening, and the new unit has to meet the thermal limit above. The survey is when we look at the span, the size of the timbers and what sits above the ceiling, and we say whether a structural calculation will be needed.
Where the roof is flat, the opening also changes the fall of the deck around it, and the upstand has to be built high enough for the membrane to be dressed up it. A pitched roof asks different things of the work: the flashing is matched to the covering, and the battens and felt around the opening are cut and lapped so water runs over the joins.
A like-for-like swap into an opening that is already framed is simpler, but the notification rule still turns on whether the frame goes.
Fire escape in a loft
Approved Document B sets the rule on means of escape. As an escape route, a window is only recognised on storeys at no greater height than 4.5m above the ground. So a house of two storeys with a loft conversion has to be given a protected stair, as a roof window cannot act as the escape. A bungalow, or a chalet bungalow, can have a roof window serving its rooms in the roof, provided they sit inside that height.
Our page on roof windows and fire escape explains how that is checked, and the loft conversion roof windows guide covers sizing for a room in the roof.
Daylight and planning are separate questions
Houses in England face no daylight requirement under the Building Regulations at all. Part O deals with overheating in new dwellings only, so it does not apply to a rooflight in an existing house.
Planning is a separate question from Building Regulations. Permitted development can cover a rooflight, and the conditions that apply are in our rooflight planning guide. A rooflight on a listed house needs a separate listed building consent, whatever permitted development might allow, while an unlisted house can lose the right under an Article 4 direction or under a restriction placed on an earlier planning permission. The address is what we check, and the council makes the decision.
What the survey settles
The survey covers measuring the opening and looking at the structure around it, and we tell you which parts of the job need notifying. The written quote then shows the notification as its own line beside the unit, the flashing and the roof work.
- Notifiable work named on the quote
- Part L limit stated for each unit
- Building Control route confirmed
Work on every quote meets the current Building Regulations, and it comes with our 10-year guarantee on workmanship together with whatever warranty the maker gives. To start, book a free survey, or read how we work across every kind of rooflight job.
Related questions
Does a like-for-like swap need Building Control?
A whole rooflight replaced with another, frame and glass, is notifiable. A fresh glass unit fitted to a sound frame is not. Which of the two your roof falls under is settled at the survey.
Who pays the Building Control fee?
The fee is part of the quote where the work is notifiable, so it is shown with the other costs and you do not meet it separately.
Do I get a certificate afterwards?
A completion certificate is issued by Building Control after the work has been signed off, and it is yours to keep with the house documents. Where a copy comes to us, we pass it straight on.
Is a roof window held to a different limit from a rooflight?
Yes. Part L 2021 puts the figure for a rooflight at 2.2 W/m²K, but a roof window is measured as a window and needs 1.4 W/m²K, or alternatively Band B for window energy.