Roof Lanterns & Flat Skylights: The 2026 Guide to Flat Roof Extensions

A flat roof extension is highly cost-effective but can leave your new living space feeling dark and dreary. Discover how Korniche roof lanterns and flat skylights instantly flood your home with natural light.

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A modern grey roof lantern adds instant architectural height and floods the space below with natural sunlight.

Letting light into our homes is exactly what windows were designed for. However, when you build a brand-new home extension across the back of your property, you inevitably lose the original kitchen or dining room windows. This can frequently leave the inner core of your home feeling dark and gloomy.

If you are going down the traditional build route, you generally have three main roofing options: lean-to, gable-ended, or flat roofs.

• Pitched Roofs (Lean-to & Gable): These look traditional but are highly restricted by the position of your first-floor windows. A gable roof is also the most expensive and complex structure to build.
• Flat Roofs: Flat roofs are highly cost-effective and face almost no height restrictions. However, relying solely on standard patio doors for natural daylight can leave the deep internal rooms entirely reliant on electric lighting during the day.

This is where structural glass enters the equation. By introducing a premium aluminium roof lantern or a flush flat skylight, you completely solve the lighting dilemma.

1. What is a Roof Lantern?

A roof lantern is effectively a hybrid structural solution. Think of a traditional flat roof, but with a raised supporting up-stand (a ‘kerb’), topped with a pitched, pyramid-style glass box.

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The Korniche Lantern delivers incredible strength with exceptionally slim aluminium sightlines, maximising the glass area.

At KJM Group, we highly recommend the Korniche Roof Lantern. Engineered from premium, thermally broken aluminium, it delivers immense structural strength while maintaining incredibly slim sightlines. This means you see more glass and less frame.

The Advantages of a Lantern

• Architectural Height: Because the glass pitches upwards, it immediately makes a standard 2.4m flat ceiling feel dramatically taller and more expansive inside.
• The ‘Centrepiece’ Effect: A lantern is perfectly designed to sit directly above a kitchen island or a large family dining table, creating a stunning focal point.
• Light Capture: The angled glass panes actively catch the sun as it moves across the sky from morning until evening.

2. What is a Flat Roof Light?

While lanterns add height, a Flat Roof Light (or Flat Skylight) is designed to be entirely unobtrusive. Rather than pitching upwards in a pyramid shape, the glass sits almost entirely flush with your exterior flat roof.

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The Korniche Flat Roof Light provides a completely uninterrupted, minimalist view of the sky above.

The Korniche Flat Roof Light is the ultimate choice for minimalist, ultra-contemporary extensions. It features an innovative “edge-to-edge” glass design, meaning water simply glides completely off the surface without pooling against an aluminium frame.

The Advantages of a Flat Skylight

• Uninterrupted Views: There are absolutely no internal glazing bars to break up your view of the clouds or stars.
• Exterior Roofline: Because it sits flush, it is invisible from ground level outside, satisfying strict planning departments in sensitive areas.
• Ultra-Modern Aesthetic: Internally, it acts as a simple, highly elegant “window to the sky” that suits sleek, handle-less modern kitchens perfectly.

3. Interactive: Lantern vs Skylight Assessor

Not sure which roof glazing option suits your new extension best? Use our quick assessment tool below.

4. Can I Retrofit to an Existing Flat Roof?

This is possibly the best-kept secret in home improvement: Yes, you can easily retro-fit a roof lantern onto an existing flat roof.

If you have an old, dark extension built in the 1980s or 90s, the transformation a new roof lantern can deliver is incredible. It takes a purely utilitarian, gloomy room and transforms it into something absolutely spectacular without the massive cost of a full rebuild.

5. Essential Glass Technology (Self-Cleaning & Solar)

When you are installing a large expanse of glass directly overhead, standard window glass is simply not fit for purpose. You must specify high-performance technology to ensure the room is actually usable in extreme temperatures.

• Solar Reflective Coatings: High-performance Low-E glass uses a transparent microscopic film of metal oxide. In summer, this coating physically reflects the intense infrared heat of the sun away, preventing your extension from becoming a greenhouse. You can choose beautiful tints like Blue or Aqua to further reduce harsh glare.
• Argon Gas Fills: During the winter, the inert argon gas trapped between the glass panes acts as a dense thermal blanket, keeping your expensive central heating inside the room.
• Self-Cleaning Technology: This is highly recommended for roofs. A dual-action coating uses UV light to break down organic dirt (like bird droppings). When it rains, the water “sheets” across the glass rather than beading, washing the dirt away completely streak-free.

6. Why Choose a Local Hampshire Installer?

7. Frequently Asked Questions