Does replacing a rooflight need Building Regulations approval?

The rule in one paragraph

The Building Regulations treat windows, roof windows and rooflights as controlled fittings. When you put one in, whether it is the first in that roof or a replacement for an old one, the work has to meet the standards for thermal performance and must be reported to building control. The line between notifiable and not is drawn at the frame. If the frame and the glass both go, you are fitting a new controlled fitting. If the frame stays and only the sealed glass unit inside it is changed, you are renewing a component, and no notification is needed.

The rules below are for England. Our wider guide to rooflights and the Building Regulations covers the full set of rules, including those that apply to new openings.

Which replacements count as a whole rooflight

A few common jobs fall on the notifiable side of the line. An old polycarbonate dome taken off its kerb and replaced with a new flat rooflight is one. A tired roof window lifted out of the rafters and a new one fitted in its place is another. A roof lantern removed and replaced with a new lantern, even to the same size, also counts, because the frame is new.

Jobs on the other side include the following.

• A misted double-glazed unit lifted out of a sound aluminium or timber frame and a new sealed unit set in
• New glass panels fitted into a lantern frame that stays
• New seals or beads fitted around glass that stays

If you are not sure which side your job is on, the quickest test is to ask what is left on the roof once the work is finished. If the old frame is still there, the job is a component change. If everything that was visible from the roof is new, it is a whole rooflight. Our page on replacing the glass or the whole unit helps you decide which one a misted rooflight needs.

What the new rooflight has to achieve

The thermal limits for replacement fittings in existing homes come from Part L. Table 4.2 of the 2021 edition gives a roof window the window limit: 1.4 W/m²K, or Band B on the window energy rating scale. A rooflight, meaning a flat or lantern-style unit in a flat roof, has its own limit, 2.2 W/m²K.

The two limits are different because the products are different. A roof window sits in the plane of a pitched roof and is made and tested like a window. A flat rooflight or lantern sits on a kerb and is a larger, site-assembled kind of unit. When we specify a replacement, the quote spells out which unit and glass are proposed, so you can see which limit applies and that the unit chosen meets it.

The limits are a minimum. If you are replacing a misted unit that has gone cloudy because the seal has failed, a modern unit will usually perform better than the one it replaces, and the limits are rarely the difficult part of the job.

How notification works

A notifiable job has to be reported to building control, and there are two routes. The first is the building control team at your local council. The second is a private inspector, who since April 2024 holds the title registered building control approver. Both end with the same thing: a completion certificate once the work has been checked and accepted.

Where the work is notifiable, we deal with the notification ourselves, so you do not have to pick a route or fill in the forms. The paperwork is part of the job, and you keep the certificate with your house documents. A buyer's solicitor may ask for it years later, which is the main reason to keep a clean file.

A job that is not notifiable has no certificate, but we still fit the new sealed unit to the maker's instructions and note its details in the paperwork we give you at handover.

Planning permission is a separate question

Building Regulations and planning permission are two different systems with two different decision-makers. Passing one says nothing about the other. Most replacements in the same opening, with a unit of the same size and shape, change nothing about how the roof looks from outside, and permitted development usually covers them. That is not universal. Permitted development can be taken away by a condition on the planning consent or by an Article 4 direction, and it does not apply to a listed building.

For your address we look at the position and report back, though the council decides. Our guide to rooflights and planning permission explains how to check for yourself, and it is the one place we set out the permitted development conditions in full.

What to tell us at the survey

A few facts about the existing rooflight let us say, before anyone climbs a ladder, whether the job is a glass swap or a whole replacement. It helps to have the following ready.

• What the rooflight is: a roof window, a flat rooflight, a dome or a lantern
• What is wrong with it: misting between the panes, a cracked or clouded dome, a frame that no longer closes
• Whether you have any earlier certificate or paperwork for it
• Whether the roof is being re-covered soon, in which case the two jobs are best planned together

If a re-roof is coming, the notification and the roofer's programme can run together, which is the idea behind replacing a rooflight while the flat roof is re-covered. Our overview of misted rooflight replacement sets out the usual route from survey to fitting, and the survey is free.

Related questions

Does a notified replacement need an inspection?

Notified work is checked by building control, either the council team or a registered building control approver. The inspection confirms the new unit is in and meets the thermal limits. We arrange the visit as part of the notification and tell you the date once it is set.

Will the certificate matter if I sell?

It can. A buyer's solicitor may ask for evidence that a replaced rooflight was notified. A completion certificate answers that in one document, so we pass it to you when it arrives and suggest you keep it with the deeds.