Short answer: Usually yes. A new lantern means a new opening, which alters the roof structure, so under the Building Regulations 2010 the job is controlled work and the lantern has to satisfy Part L on energy. Because England classes a lantern as a rooflight, the figure for an existing home is 2.2 W/m²K, taken from Table 4.2 of Approved Document L. If the job is notifiable, we do the notifying.
Why a new lantern opening is notifiable
The question of roof lantern building regulations comes from a simple fact. Fitting one in a roof that has no opening means cutting through the roof deck and the joists beneath it, and replacing them with a structure that carries the load around the hole. That is structural work, and it falls under the Building Regulations whether the roof belongs to a new extension or an old one.
There are two things the regulations care about. The first is structure: the trimmed joists and any beam must carry the roof, the lantern and the weight of snow, and they must do it safely. The second is energy: the glass and frame are part of the thermal envelope of the house, and the regulations set limits on how much heat they can lose. Building control checks both.
Swapping an existing lantern for one of the same size on an existing kerb is a lighter case, but the replacement lantern still has to meet the energy limit, and it counts as controlled work. We tell you at survey which of the two situations your job is, and notify accordingly.
The England figure: 2.2 W/m²K
Approved Document L volume 1 limits the heat loss of any new or replacement glazing in an existing English home. Table 4.2 caps a rooflight at a U-value of 2.2 W/m²K. Because a lantern is classed as a rooflight, that cap is the one it must meet. A roof window is a different product and is held to Window Energy Rating band B or a U-value of 1.4 W/m²K.
A U-value is a measure of heat loss, so a lower figure means a warmer room. A well-specified double-glazed lantern with a thermally broken frame and a low-emissivity coating can meet the limit. A cheaper or older design may not. That is one reason a specification matters. Ask any supplier for the U-value of the whole lantern, not just the centre of the glass, since the frame counts too.
For triple glazing, coatings and how they shift the numbers, read the full Part L guide to rooflight U-values. For the choice of frame, see the aluminium or uPVC roof lantern guide.
| Product | Limit |
|---|---|
| Roof lantern (rooflight) | 2.2 W/m²K |
| Roof window | Band B on the Window Energy Rating, or 1.4 W/m²K |
If your home is in Wales
Flintshire and Wrexham are covered by the Welsh Building Regulations 2010, and the energy requirements sit in Approved Document L (Wales), 2022 edition. The Welsh document has its own table numbering, and a Welsh house is checked against the Welsh document, even where a figure matches the English one. We check the Welsh document for your job and specify the lantern to meet it, and the notification goes to Flintshire County Council or Wrexham County Borough Council, depending on the address, or to a registered building control approver.
The Welsh Government publishes the requirements on gov.wales.
Who deals with the paperwork
You do not have to. Roof lantern building control starts with a notification, and we make it where the work is notifiable; the council and a registered building control approver are both options, the approver being the title that replaced private inspector in April 2024. Building control can inspect at set stages, for example the trimmed opening. Sign-off by the council produces a completion certificate, and sign-off by an approver produces a final certificate.
That certificate matters later. A buyer's solicitor asks for it when you sell the house, and a lantern without one can hold up a sale. Getting it at the time costs far less trouble than chasing it years afterwards.
- Is a new opening being cut?
- Does the structure around it need a beam or doubled joists?
- Does the lantern's U-value meet the limit?
- Is the notification made before work starts?
- Do you get the certificate at the end?
Regulations are not the same as planning
Building Regulations and planning permission are separate. Building Regulations deal with how the work is built. Planning deals with how it looks and where it goes, and whether a lantern needs an application depends on the property and where it stands, so our planning permission guide covers it. For a listed building, listed building consent is needed on top of anything else.
The roof lantern installation page follows the whole job, survey to clean-up. Ready to go ahead? A survey of the roof comes first, where we confirm the notification route, and a written, fixed price follows. After the lantern is fitted, a 10-year guarantee in writing covers our workmanship. Get a free quote
Lanterns and the regulations: what else people ask
Does replacing an old lantern on the same kerb still need notifying?
Yes. A replacement lantern in England is still controlled work, since it must reach the energy limit, and we handle the notification and check the kerb at the same time.
Will I get a certificate at the end?
Yes. If a registered building control approver handled the job, the certificate you receive is a final certificate; the council issues a completion certificate. Keep it with your house papers, since it will be asked for when you sell.
Does a lantern in a conservation area need extra approval?
The Building Regulations bear on a conservation-area lantern just as they do elsewhere. Planning is a separate matter, and a council can have removed permitted development rights in some areas. Your survey flags it, and we point you to the planning guide.