Roof Lantern vs Skylight: What Is the Difference?
A roof lantern sits raised above the roofline on a kerb frame and lets light in from multiple angles through sloping glass panels. A skylight sits flat or near-flat within the roof plane and brings light in from directly above. Both add natural light to a room, but they suit different roof types, budgets and design styles.
If you are planning an extension or a loft conversion in the UK and trying to decide between a roof lantern and a skylight, the difference comes down to three things: the shape of your roof, how much light you need and how much headroom you want to preserve. This guide covers both options so you can make the right call before buying.
What Is a Roof Lantern?
A roof lantern is a glazed structure that sits proud of the roof surface. It has a raised frame, typically 150mm to 400mm above the flat roof deck and angled glass panels that run up to a central ridge. Because the glass panels face in multiple directions, a roof lantern catches light from a wider arc of the sky than a flat rooflight can.
Roof lanterns are most common on flat roof extensions, orangeries and kitchen extensions. They create a strong visual centrepiece inside the room and, on the exterior, give the building a more traditional or premium appearance.
What Is a Skylight?
A skylight, also called a rooflight or roof window, sits within or flush to the roof surface. On a flat roof it typically sits at a low pitch of 5 to 15 degrees to allow rainwater to drain. On a pitched roof it can be either a fixed unit or an opening roof window that follows the slope of the roof.
Flat rooflights are the most common choice for modern extensions because they keep the roofline clean and uninterrupted. They are also generally more affordable than roof lanterns and available in a wider range of standard sizes.
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This is where the two products genuinely differ in everyday use. A roof lantern brings in light from multiple angles throughout the day. In the morning, the east-facing panels pick up early light. By afternoon, the west panels take over. The result is a room that feels consistently bright regardless of where the sun is sitting.
A flat rooflight brings light in from directly above. It performs best when the sun is high, which in the UK means summer months and midday hours. In winter or on north-facing roofs, a flat rooflight can feel noticeably darker than a roof lantern of equivalent glazed area.
If maximum light is the priority, a roof lantern or a combination of multiple flat rooflights is the better route.
Which Roof Type Each One Suits
Roof lanterns are designed exclusively for flat or very low-pitch roofs. The kerb frame needs a level surface to sit on and the structural load is concentrated at the four corners of the frame. They are not suitable for pitched roofs.
Flat rooflights also sit on flat roofs but are available in a much wider range of profiles. Frameless rooflights give a near-invisible finish flush to the roof membrane. Pitched roof windows follow the slope of a tiled or slate roof and are a completely different product category from either.
The Difference in Installation Cost
Roof lanterns cost more to supply and install than flat rooflights of a comparable glazed area. The kerb frame, the ridge bar and the multiple glass panels all add material cost. Installation is also more involved because the frame needs to be perfectly level and the glazing units are heavier to lift into position.
As a rough guide for the UK market in 2026:
- A mid-size flat rooflight (1000mm x 1500mm) typically costs between £500 and £1,200 supplied, with installation adding £300 to £600.
- A roof lantern of equivalent footprint typically costs between £1,500 and £4,000 supplied, with installation adding £500 to £1,000.
These are indicative ranges. The actual cost depends on the specification, the glazing type and your installer's day rate. Our skylight installation cost guide covers this in more detail
Planning Permission: Does Either One Need It?
In most cases, neither a roof lantern nor a flat rooflight requires planning permission under Permitted Development Rights, provided the work does not exceed certain height limits and the property is not in a conservation area or listed. The permitted development limit for a roof addition on a flat roof is that it must not extend more than 150mm above the existing roof plane.
A roof lantern that sits higher than 150mm above the roof surface may require planning permission depending on local authority interpretation. If you are unsure, check with your local planning office before ordering. Our planning permission guide for skylights covers the rules in full.
Which One to Choose for a Kitchen Extension
Kitchen extensions are the most common setting for both products. A roof lantern over the dining or living area of a kitchen extension creates a dramatic centrepiece and transforms how the space feels. It is the right choice if the extension is large enough (typically 3m x 3m or more) to carry the structure visually.
For narrower or longer extensions, a run of two or three flat rooflights often works better. They let more flexibility in positioning, are lighter on the structure and keep the exterior profile low. Our kitchen rooflights collection includes both options sized for typical UK extension footprints.
Not sure which is right for your project? Browse our full range of roof lanterns and flat rooflights, or contact us and we will help you choose the right unit for your roof type and budget.
Summary: Key Differences at a Glance
|
Feature |
Roof Lantern |
Flat Rooflight |
|
Roof type |
Flat only |
Flat or pitched |
|
Light quality |
Multi-directional all day |
Directly overhead |
|
Visual impact |
High, structural centrepiece |
Low profile, clean finish |
|
Supply cost |
£1,500 to £4,000+ |
£500 to £1,200 |
|
Planning permission |
Sometimes required |
Usually not required |
|
Best for |
Large open-plan extensions |
Narrow extensions, budgets |
Frequently Asked Questions
- Is a roof lantern the same as a skylight?
- Which lets in more light, a roof lantern or a skylight?
- Can you put a roof lantern on a pitched roof?
- Do roof lanterns need planning permission in the UK?
- How much more does a roof lantern cost than a skylight?
- What size roof lantern do I need for a kitchen extension?
- Which is more energy efficient, a roof lantern or a skylight?
- Are roof lanterns and skylights watertight?
No. A roof lantern is a raised glazed structure that sits above the roof surface on a kerb frame with angled glass panels. A skylight (or rooflight) sits within or flush to the roof plane. Both let natural light into a room but they look different, cost different amounts and suit different projects.
A roof lantern typically lets in more light per square metre of footprint because its angled panels catch light from multiple directions throughout the day. A flat rooflight is most effective when the sun is directly overhead. For north-facing extensions or UK winter light, a roof lantern is the stronger performer.
No. Roof lanterns are designed for flat or very low-pitch roofs only. They require a level kerb frame to sit on. For a pitched roof, a roof window or pitched roof skylight is the correct product.
Under Permitted Development Rights, additions to a flat roof must not protrude more than 150mm above the existing roof surface. Many roof lanterns exceed this height and may therefore require planning permission. Always check with your local planning authority before ordering, particularly if your property is in a conservation area or is listed.
A roof lantern typically costs two to four times more than a flat rooflight of comparable glazed area. Supply costs for a mid-size flat rooflight start from around £500, while a roof lantern of similar footprint typically starts from £1,500. Installation costs are also higher for a roof lantern due to the heavier glazing and more complex frame.
As a general guide, a roof lantern should cover between 15% and 25% of the floor area of the room below to avoid under-lighting or structural over-engineering. For a typical 4m x 5m kitchen extension (20 sqm), a roof lantern of around 1.5m x 2m to 2m x 2.5m is appropriate. Always check with a structural engineer if you are unsure about the load-bearing requirements.
Both can deliver excellent thermal performance when specified with thermally broken aluminium frames and Low-E glass. Fixed flat rooflights from Rooflights and Skylights UK achieve a U-value of 1.0 W/m²K with double glazing and 0.5 W/m²K with triple glazing, making them a strong choice for projects with demanding thermal targets.
Yes. A correctly installed roof lantern or flat rooflight is fully watertight when it sits on a level upstand with the roof membrane turned up and sealed. Fitting by a qualified roofer gives you a long-lasting weatherproof finish on either product.