NOTE Nº 0243 · REV B

Roof Lanterns: Cost & Options

How much does a roof lantern cost in the UK? Covers sizes, glazing types, installation prices from £1,500 to £8,000+, and what to look for.

By The Renovation Notes Team · 8 min read · Published 22 October 2025 · updated within the last month · Sources checked 2 October 2026

In short

A standard roof lantern costs £1,500–£8,000+ supplied and fitted, depending on size and frame material. Aluminium frames with double-glazed units are the most common choice for extensions and flat-roof additions.

A roof lantern is a raised, glazed framework that sits on a flat or near-flat roof to flood a room with natural light. Unlike a simple flat rooflight, a lantern has a pitched profile, typically a ridge running along its centre, which sheds rainwater effectively and creates more headroom beneath. They are most commonly installed on single-storey rear extensions, kitchen-dining rooms, and orangeries.

Supplied and fitted, expect to pay £1,500–£8,000+ per lantern, depending on size, frame material, and glazing specification. A modest 1.0 m × 1.5 m lantern costs around £1,500–£2,200 fitted in uPVC or £2,000–£3,000 in aluminium; a larger 2.0 m × 3.0 m triple-glazed aluminium lantern with a quality installer can easily reach £5,500–£8,000 or more.

Types of Roof Lantern

By Frame Material

Costs are for one lantern, frame and glazing supplied without fitting, and the spread within a row is mostly size:

Material	Typical Cost (supply only)	Lifespan	Thermal Performance	Notes
uPVC	£600–£2,000	20–30 yrs	Moderate	Bulkier sightlines, limited colours
Aluminium (powder-coated)	£1,000–£5,000	35–50+ yrs	Good (thermally broken)	Slim profiles, huge colour range via RAL
Timber	£1,500–£6,000	30–60 yrs (with maintenance)	Excellent	Classic look, needs repainting every 5–10 yrs
Aluminium-timber composite	£2,500–£7,000	40–60 yrs	Excellent	Timber interior, alu exterior, best of both

Thermally broken aluminium is the most common choice: slim sightlines maximise the glazed area, it is low-maintenance, and the thermal break keeps the cold outer parts of each section separate from the warm inner ones.¹

By Glazing

Double glazing: the standard, typically in 24–28 mm argon-filled sealed units¹
Triple glazing: lowers the U-value further and adds roughly £200–£1,500 per lantern depending on size; worthwhile in an exposed or north-facing position
Self-cleaning glass: a photocatalytic coating breaks down organic dirt in daylight so that rain can wash it away.² It is standard on some makers’ lanterns and adds roughly £100–£300 on others, and is worth having wherever cleaning is difficult.¹ That price is per lantern.
Solar control glass, reduces summer heat gain; useful if the room faces south or south-west; adds £80–£200 per lantern

Specify laminated glass for the inner pane so that a broken pane stays in place rather than falling into the room; makers such as Korniche offer it as an option.¹ Building Regulations Approved Document K deals with glazing people can walk into, in doors and low in walls, not with overhead glazing, so this is good practice and the norm for quality lanterns rather than a Part K requirement.³

Typical Sizes and Costs

Manufacturers generally quote in external frame size.¹ The structural opening in the roof is smaller than that, by an amount that depends on the kerb or upstand detail, so check which dimension a quote refers to.

External Size	Frame Material	Glazing	Typical Fitted Cost
1.0 m × 1.5 m	uPVC	Double	£1,500–£2,200
1.0 m × 1.5 m	Aluminium	Double	£2,000–£3,000
1.5 m × 2.5 m	Aluminium	Double	£3,000–£4,500
2.0 m × 3.0 m	Aluminium	Double	£4,500–£6,500
2.0 m × 3.0 m	Aluminium	Triple	£5,500–£8,000
2.5 m × 4.0 m	Aluminium-timber	Triple	£7,000–£12,000+

Prices include VAT at 20%, supply of the unit, and a typical installation on an accessible flat roof with an existing structural opening. They exclude making good the ceiling, any structural alterations to the opening, or scaffolding if access is difficult.

What Drives the Price

Size is the dominant factor. Glass and frame cost scale roughly with area; the installation labour (typically one to two days for a pair of fitters) scales much more slowly.

Frame material affects both supply cost and long-term value. Aluminium costs more than uPVC upfront but commands a better resale impression and lasts significantly longer.

Glazing specification adds cost incrementally. Triple glazing and solar control are genuine upgrades; self-cleaning glass is worth it almost everywhere given the difficulty of cleaning overhead glass.

Structural work, if the roof structure needs a lintel or trimmer joists to create or enlarge the opening, add £300–£1,500 for a carpenter and possibly a structural engineer’s calculation (£250–£600).

Access and scaffolding, most lantern installs on single-storey extensions are done from ladders or a small tower scaffold. On a two-storey structure or awkward pitch, scaffolding can add £500–£2,000.

Planning and Building Regulations

Whether a lantern needs planning permission depends on how it is judged. As an alteration to a roof, under Class C, a rooflight may stand no more than 150 mm proud of the roof, which a raised lantern usually exceeds.⁴ Built as part of a new single-storey extension, it is judged with the extension, and must keep within that extension’s permitted development limits, including its height.⁵ Because the answer turns on the details, a lawful development certificate is worth having before you order, and a listed building needs listed building consent in any case.⁶

Building Regulations (Approved Document L, Volume 1) apply to the thermal performance. The limiting U-value for a rooflight in an existing dwelling is 2.2 W/m²K, which most quality double-glazed lanterns beat comfortably.⁷ Part L asks for a rooflight’s U-value to be calculated in the horizontal position, which gives a higher figure than the vertical value often quoted for glass, so ask the supplier for the horizontal figure.⁷ Note that Part L treats a rooflight, which sits out of the plane of the roof on a kerb or upstand, differently from a roof window set in the plane of the roof: a roof window has to reach 1.4 W/m²K.⁷ Approved Document L also caps the combined area of windows, rooflights and doors in an extension at 25% of its floor area, plus the area of any openings the extension removes; going over is allowed if a calculation shows the extension performs no worse.⁷

Always check with your local planning authority if you are in a designated area.

Roof Lantern vs Flat Rooflight

Feature	Roof Lantern	Flat Rooflight (flush)
Profile	Raised/pitched ridge	Flush or slightly proud
Light quality	Diffused from multiple angles	More direct, overhead
Drainage	Self-draining via pitch	Requires fall in roof deck
Visual impact	Statement feature	Discreet
Cost (1.5 m × 2.5 m)	£3,000–£4,500 fitted	£1,200–£2,800 fitted
Cleaning	Harder, steeper glass	Easier with long-handled tool

The right choice depends on the architectural language of the extension. A lantern suits orangery-style or classical buildings; a flush rooflight suits a contemporary flat-roof extension where a low profile is desired.

How to Choose a Supplier

Check fabrication quality, look for thermally broken sections (no metal bridge connecting interior and exterior of the frame) and argon-filled sealed units.
Ask for U-value documentation: a reputable supplier will provide a calculated or tested U-value for the whole lantern, in the horizontal position that Part L uses.
Verify the warranty: 10-year warranties are common from established makers, but check what the frame and sealed-unit cover each include.¹
Use FENSA or Certass-registered installers for a replacement. Both are government-authorised competent person schemes for replacement rooflights in existing homes.⁸ Installing a replacement rooflight in an existing home is work they can self-certify, notifying the local authority for you, so you need no separate Building Regulations certificate.⁹ A lantern in a new extension or a new opening is covered by the Building Regulations application for that work instead.
Get three quotes, fitting quality varies; the cheapest quote is not always the best value if the installer uses inferior sealant or omits flashing details.

A well-installed roof lantern with a quality frame and double or triple glazing will transform a dark extension and add genuine appeal to a home. Spending an extra £500–£1,000 on a thermally broken aluminium unit over a uPVC equivalent almost always proves worthwhile over a 20-year horizon.

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.

References (9)

Figures in this note were checked against the sources below on 2 October 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

1technicalsupplier figureKorniche, guidance.RN-4ODGLOA roof lantern maker's product page. It describes the insulated core that forms a thermal break in its aluminium sections, separating the cold outer parts from the warm inner ones.
2technicalsupplier figurePilkington, guidance.RN-WLOLLHThe glass maker's page for its self-cleaning glass range. It explains that the coating breaks down organic dirt photocatalytically in daylight so that rain washes it off.
3technicalvery strongMinistry of Housing, Communities and Local Government.RN-XH6E39The standard that decides whether a loft ladder is legal and when a raised deck needs a balustrade. Published 3 January 2013, it covers protection from falling, collision and impact including stairs, ladders, ramps, guarding and vehicle barriers. Paragraph 1.31 states that retractable ladders must not be used as a means of escape. Paragraph 1.32 permits a fixed ladder, with fixed handrails on both sides, only for access in a loft conversion containing one habitable room, and only where there is not enough space without altering the existing space for a compliant stair, which is the rule that catches most loft ladder installations. Paragraph 1.29 restricts alternating tread stairs to loft conversions. For a private stair the maximum pitch is 42 degrees (Table 1.1 note 1), the normal relationship between rise and going is twice the rise plus the going between 550mm and 700mm, and for dwellings external tapered steps forming part of the building need a going of at least 280mm. Paragraph 3.1 requires guarding wherever it is reasonably necessary for safety at the edge of a floor, gallery, balcony, roof, light well, basement or similar sunken area. Paragraph 3.2 requires guarding to be at least the height in Diagram 3.1, allows any wall, parapet or balustrade to serve as guarding, and requires it to resist the loads in BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1, with BS 6180 for barrier and infill panel design. Handrails should be positioned 900mm to 1000mm from the pitch line or floor.
4technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-5QRXP7Class C permits any other alteration to the roof of a dwellinghouse, which is the right rooflight and Velux loft conversions rely on. Paragraph C.1(b) makes development not permitted if the alteration would protrude more than 0.15 metres beyond the plane of the roof slope, measured perpendicular to the original roof plane, and C.1(c) if the highest part of the alteration would be higher than the highest part of the original roof. C.1(d) excludes chimneys, flues, soil and vent pipes and solar equipment from the class, and condition C.2 requires any window in a roof slope forming a side elevation to be obscure-glazed and non-opening below 1.7 metres above the floor of the room.
5technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-Z0XQ8VParagraph A.1 sets the householder extension limits: buildings may not cover more than 50 per cent of the curtilage (A.1(b)); a single-storey rear extension may not extend more than 4 metres beyond the rear wall of a detached house or 3 metres for any other house, nor exceed 4 metres in height (A.1(f)), rising to 8 metres and 6 metres under the larger home extension route (A.1(g)); an extension of more than one storey may not extend more than 3 metres beyond the rear wall or be within 7 metres of the rear boundary (A.1(h)); eaves within 2 metres of a boundary may not exceed 3 metres (A.1(i)); a side extension may not exceed 4 metres in height, have more than one storey or be wider than half the width of the original house (A.1(j)). Paragraph A.2 removes cladding and side or multi-storey rear extensions on article 2(3) land such as conservation areas. A.3 requires materials of similar appearance and obscure-glazed, non-opening upper-floor side windows unless the opening part is more than 1.7 metres above the floor, and A.4 sets the neighbour consultation (prior approval) procedure with its 42-day determination period.
6technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-XN22L9The provision that decides when listed building consent is actually needed, and the answer to the common overstatement that any alteration to a listed building requires consent. Section 7(1): 'no person shall execute or cause to be executed any works for the demolition of a listed building or for its alteration or extension in any manner which would affect its character as a building of special architectural or historic interest, unless the works are authorised under section 8.' The trigger is therefore effect on character as a building of special architectural or historic interest, not alteration as such, so work with no effect on that character falls outside the restriction. Section 7(2) makes subsection (1) subject to section 33(1) of the Planning Act 2008, which excludes the requirement for other consents where development consent is required. Authorisation itself comes from section 8.
7technicalvery strongMinistry of Housing, Communities and Local Government.RN-L0FCJXThe in-force U-value tables a DIY insulation or door note must quote, with the exact numbers. Table 4.2, limiting U-values for new fabric elements in existing dwellings, sets roof 0.15, wall 0.18, floor 0.18, swimming pool basin 0.25, window 1.4 or Window Energy Rating Band B minimum, rooflight 2.2, doors with more than 60 per cent of the internal face glazed 1.4 or Doorset Energy Rating Band C minimum, and other doors 1.4 or Doorset Energy Rating Band B minimum. Table 4.3, for existing elements, gives a roof threshold of 0.35 and an improved value of 0.16, which is the figure a loft insulation note needs: paragraph 4.12 says a retained element whose U-value is higher than the column (a) threshold, for example through a loft or garage conversion, should be upgraded to the column (b) value. Paragraph 4.13 allows a lesser upgrade only where the improved value is not technically or functionally feasible or would not achieve a simple payback of 15 years or less. Paragraph 4.8 requires a replacement element to be no worse than the one it replaces as well as meeting Table 4.2. Paragraph 4.10 gives the heritage exception: where character must be maintained, a centre pane U-value of no more than 1.2 or low-emissivity secondary glazing. Note 9 records that the timber window concession of 1.6 or Band C ended on 14 June 2023. The 2021 edition came into force on 15 June 2022; a 2026 edition exists at https://assets.publishing.service.gov.uk/media/69c122a6cfa346b9d4704a55/ADL1_2026.pdf.
8technicalvery strongMinistry of Housing, Communities and Local Government.RN-SAMO3MThe official list of competent person schemes whose members can self-certify certain building work instead of getting building regulations approval, published 4 April 2013 and last updated 12 March 2018. Named schemes with contact numbers include ATTMA, APHC, Assure Certification, Blue Flame Certification, the British Board of Agrement, BESCA, Capita Gas Registration and Ancillary Services trading as Gas Safe Register, CIGA, Certass, Certsure LLP trading as NICEIC, the Elmhurst Airtightness Scheme, Fensa Limited, HETAS Limited, NAPIT Registration Limited, the National Federation of Roofing Contractors trading as CompetentRoofer, and OFTEC. Two footnotes matter: the Gas Safe Register is not technically a competent person scheme although in practice its installers carry the same building regulations responsibilities, and Benchmark Certification Limited ceased to operate as a competent person scheme on 10 February 2017, becoming part of NAPIT Registration Limited that day. Installers joining an electrical scheme are added to the single electrical competent person register.
9technicalvery strongThe National Archives (legislation.gov.uk), guidance.RN-BP3IWGSchedule 3 item 12 lets registered installers (APHC, BESCA, Certsure, HETAS, NAPIT) self-certify sanitary installations in a dwelling that involve no shared or underground drainage.