Short answer: The cost of fitting a roof lantern rests on its size and shape, the frame, the glass specification, whether a kerb exists or a new opening must be cut, any structural work, how easy the roof is to reach and the finish inside. We do not name a price without a survey. The quote we write once the survey is done is a fixed one for the whole job, so nothing is added later.
Size and shape set the starting point
When people ask about roof lantern installation cost, they usually want one number. A lantern does not come in one size, so there is no single number. A small lantern over a hallway is one job. A large one across a kitchen diner is another. The bigger the lantern, the more material goes into the frame and the more glass sits above the room, and the heavier it is to lift into place.
Shape matters as well as size. A simple rectangular lantern with a single ridge is the plainest form to make. Lanterns with a pyramid shape, a hipped end, a curved glazing bar or an unusual outline take longer to build. A lantern that has to fit an awkward opening, such as a roof with a splayed wall or a corner, is made to order, and made-to-order work is priced accordingly.
The roof lantern sizes guide explains how the proportions work.
Frame, glass and finish
The frame is the second big driver. Aluminium and uPVC differ in material, in how they are made and in the colours available, and the roof lantern price sits differently for each. A dual-colour finish, a special RAL colour or a decorative ridge cresting adds to the making. Aluminium and uPVC are weighed up in the guide to choosing between aluminium and uPVC.
The glass specification is the third. Standard double glazing sits at one end. Each of these adds to the price of the unit: triple glazing, a solar-control coating, a self-cleaning outer pane, a laminated inner pane or a tint. A lantern over a south-facing kitchen extension often justifies solar control. A lantern over a shaded room may not.
It is worth deciding which of these matter for the room rather than asking for the most of everything, because glass is where a lantern's cost can climb without a change you would notice. Ask for the specification written down, and compare quotes on that basis.
- Frame material and colour
- Single or dual colour finish
- Double or triple glazing
- Solar-control or self-cleaning glass
- Fixed or with opening vents
A new opening or an existing kerb
The biggest swing in the job is what the lantern is replacing. If there is already a kerb on the roof, with an old lantern or rooflight on it, a replacement is a much more contained job. The old unit comes off, the kerb is checked, the new lantern goes on and the flashing is made good. If the roof is solid and has no opening, a hole has to be cut, the joists trimmed around it, a kerb built and the roof covering tied into that kerb.
That second job involves carpentry, structural design, roofing and an internal finish, and each is a cost. The detail of the retrofit is in the guide to fitting a lantern to an existing flat roof. The short version for pricing is that a new opening takes longer and has more parts than a swap, and the quote shows that.
Structure, access and the finish inside
Cutting an opening in a flat roof interrupts the joists, and the joists around it have to carry the load that the cut ones used to. Sometimes that means doubling up timbers, and on a wider opening it can mean a steel beam. An engineer may be needed to size it. Where the roof structure is sound and the opening fits between joists, little extra is needed. If the structure falls short, the structural work gets its own line on the quote.
Access is a cost people forget. A lantern is heavy and awkward. A house with an open drive and a flat roof that is easy to reach is a simpler day than a terrace with only a narrow side passage, or an extension at the back of a house with no route except through the living room.
Inside, the finish also counts. A new lantern needs a plastered or lined reveal where the opening meets the ceiling, and a new opening means making good the ceiling and painting. Some people arrange the decorating themselves, and others want it all done in one go. We work in lived-in homes, with dust sheets down and a clean-up before we leave, but the finish you want is part of what is priced.
| Factor | Simpler job | Bigger job |
|---|---|---|
| Opening | Existing kerb | New opening and kerb |
| Structure | Fits between joists | Trimming or a steel |
| Access | Clear route to the roof | Narrow passage or crane |
| Finish inside | Reveal left to you | Plastered and painted |
Why the price comes after a survey
A lantern is made to measure, and everything above depends on the roof, which cannot be judged from a photograph. The survey is where we measure the opening, look at the joists and the roof covering, check the route to the roof and talk through frame, glass and finish. It also confirms whether Building Control needs to be notified, which for a new opening it usually does. How notification works is explained in the roof lantern Building Regulations answer, and the notifying is left to us.
After the survey you receive the price in writing, fixed. Every inclusion is listed, so each part of the cost can be seen, and once you agree the figure it stays put. A guarantee on the workmanship runs for 10 years, and it is given to you on paper. Message us on WhatsApp or phone to book the lantern survey. Get a free quote
Pricing a lantern: what people check first
Is a lantern a bigger job than a flat rooflight?
Generally, yes. A lantern is a taller product with more frame and more glass, so the job tends to involve more. For a rear extension, the flat rooflight or roof lantern guide puts the two head to head.
Can I get a price from a photo or a drawing?
We can talk through the options from a photo or plan, but the price is fixed only after a survey. A picture shows none of the roof structure, the access or the existing covering, and all three affect the price.
Does the quote include the Building Control notification?
Yes, whenever the job falls under the notification rules. We handle the notification as part of the job, so you do not need to deal with the council or an approver yourself.