Short answer: a Korniche aluminium roof lantern costs between £662 and £3,969 including VAT at Glazing Store, depending on size. A typical extension size — 1500 x 2500mm — is £1,389.32 inc VAT in standard 1.2 W/m²K clear glazing. Four things move that number: the size, the glass specification, the frame colour combination, and whether you fit it yourself or pay an installer.
Everyone asks the price question first and almost nobody answers it properly. So here is the whole picture, with the actual figures, so you can budget your extension before you speak to anyone.
How much does a Korniche roof lantern cost? Full price list
These are live Glazing Store prices for the Korniche Aluminium Roof Lantern in clear 1.2 U-value glazing, including VAT, correct as of August 2026.
| Lantern size (mm) | Price inc VAT | Typical use |
|---|---|---|
| 850 x 850 | £662.28 | Small hallway, utility, en-suite |
| 1000 x 1000 | £738.92 | Cloakroom, box-room extension |
| 1000 x 1500 | £923.24 | Galley kitchen |
| 1000 x 2000 | £1,048.72 | Side-return extension |
| 1250 x 2000 | £1,142.83 | Narrow rear extension |
| 1500 x 1500 | £1,030.82 | Square dining area |
| 1500 x 2000 | £1,237.68 | Kitchen-diner |
| 1500 x 2500 | £1,389.32 | Most common extension size |
| 1500 x 3000 | £1,542.62 | Full-width kitchen |
| 2000 x 2000 | £1,354.90 | Open-plan seating zone |
| 2000 x 3000 | £1,770.71 | Large kitchen-diner |
| 2000 x 4000 | £2,296.46 | Wide rear extension |
| 2500 x 3000 | £2,006.58 | Orangery-style room |
| 3000 x 3000 | £2,912.82 | Large open-plan space |
| 3000 x 5000 | £3,968.89 | Full orangery roof |
Two things worth noticing. First, price does not rise in a straight line with area. A 1500 x 3000mm lantern (4.5m²) is £1,542.62, while a 2000 x 2000mm (4m²) is £1,354.90 — nearly the same glass, £188 apart, because rafter count and bar spans drive the frame cost, not square metres alone. Second, the jump from 850 x 850 to 1000 x 1000 costs £76.64 for 38% more daylight. Going one size up is almost always the cheapest daylight you will ever buy.
What changes the price
1. Glass specification
Korniche lanterns come in two thermal grades: standard 1.2 W/m²K and premium 1.0 W/m²K. The upgrade is not a fixed percentage — it scales with the amount of glass:
| Size | 1.2 U-value | 1.0 U-value | Uplift |
|---|---|---|---|
| 850 x 850 | £662.28 | £680.93 | +£18.65 (2.8%) |
| 1500 x 2500 | £1,389.32 | £1,489.67 | +£100.35 (7.2%) |
| 2500 x 3000 | £2,006.58 | £2,213.66 | +£207.08 (10.3%) |
| 3000 x 5000 | £3,968.89 | £4,346.70 | +£377.81 (9.5%) |
On a small lantern the premium glass is close to a rounding error and worth taking every time. On a 3m x 5m orangery roof it is a real £378 decision — although that is also the roof losing the most heat, so it is usually still the right call. If you want the reasoning behind the numbers, our guide to U-values and home energy explains what the figure actually measures, and our winter thermal efficiency guide covers cold-weather performance.
2. Glass tint
Clear and blue tint are priced the same. Neutral costs roughly £14–£83 more depending on size — under 3% in every case. Tint changes solar gain and how the room feels in July, not how it performs in January.
3. Frame colour
This one is free. Matt Black, Matt Grey and White, in any external/internal combination, are all the same price — so a matt black exterior with a white interior costs exactly the same as all-white. Most people default to white without realising the black exterior costs nothing. Bespoke RAL colours are a separate, chargeable option: see bespoke RAL colour frames.
4. Fitting
Korniche is designed as a fully-engineered kit and is genuinely installable by a competent builder — it is the reason the system won a King's Award for Enterprise. Two people can typically fit a mid-size lantern in a couple of hours once the upstand is ready. Our step-by-step fitting guide for beginners walks through the process. The expensive part of the project is never the lantern — it is the flat-roof upstand and the structural opening beneath it.
Budgeting the whole job, not just the lantern
The lantern is one line on an extension quote. To budget realistically, allow for:
- The timber or steel upstand the lantern sits on — usually built by your roofer as part of the flat roof.
- Structural support if you are opening up an existing roof. A 3m x 2m triple-glazed lantern is a serious load; see our guide on roof lantern weight.
- Delivery — free on UK orders over £1,000, which most lanterns from 1000 x 2000mm upwards clear on their own.
- Building Regulations — a roof lantern in a new extension is covered by the extension's approval. Retrofitting into an existing roof needs Part L (thermal) and Part K (structural) sign-off. Our 2026 planning and regulations guide has the detail.
Is a Korniche worth it versus a cheaper lantern?
A budget lantern of the same size will typically save you a few hundred pounds. What you give up is glazing bar slimness (Korniche's rafters carry glass with less visible frame, so you buy more daylight per square metre), the tested thermal figures above, and a system engineered for dry-glazed, gasket-sealed assembly rather than silicone. If you are weighing brands, our comparison of how to choose the best roof lantern sets out what to check on any system.
The honest test: over a 20-year life, the difference between a cheap lantern and a Korniche works out at roughly £15 a year. The difference in how the room feels is daily.
Frequently asked questions
How much is a Korniche roof lantern? From £662.28 inc VAT for an 850 x 850mm lantern up to £3,968.89 inc VAT for 3000 x 5000mm, in standard 1.2 U-value clear glazing. The most commonly ordered extension size, 1500 x 2500mm, is £1,389.32 inc VAT.
Do Korniche prices include VAT? Yes. All prices listed at Glazing Store include VAT at 20%. Trade customers should ask about trade pricing directly.
Does the frame colour affect the price? No. Matt Black, Matt Grey and White are all priced identically in any internal/external combination. Only bespoke RAL colours carry a surcharge.
Is the 1.0 U-value glass upgrade worth paying for? On lanterns up to about 1500 x 2000mm it adds under £80 and is an easy yes. Above 2500 x 3000mm it adds £200 or more, so weigh it against how much you heat the room — but that is also where the heat loss is greatest.
What size Korniche roof lantern do I need? As a rule of thumb, size the lantern to roughly a fifth to a quarter of the room's floor area, keeping at least 300mm of roof between the upstand and any edge or wall. Since price rises far more slowly than glass area, going one size larger is usually the better-value choice.
Can I fit a Korniche roof lantern myself? Yes, if you are a competent DIYer or working with a builder. The system arrives as a pre-engineered kit with no on-site cutting or silicone glazing. The upstand must be square, level and structurally sound first.
How long does delivery take? Lead times vary with size and colour. Call the Korniche team at Glazing Store on 01604 347222 (Mon–Fri, 9am–5pm) for a current lead time on your exact specification.
Ready to price up your project? Browse the full Korniche roof lantern range — every size and colour combination priced live, with a price match guarantee — or call 01604 347222 and we will spec it with you.
Prices correct as of August 2026 and include VAT. Check the product page for current pricing.
Share:
Fitting Your Korniche Roof Lantern: A Step-by-Step Guide for Beginners