Supplied AND Installed · FENSA Registered
Korniche Slim Ridge
The slim, reduced-width ridge is Korniche's defining design feature, where a wider ridge would visibly bisect the sky view from below. Korniche's slim ridge keeps the rooflight reading as a near-uninterrupted glass plane. Combined with self-cleaning glass as standard, thermally broken aluminium and a glass U-value of 1.2 W/m²K: the slim-ridge spec for premium kitchen extensions, rear-elevation rooflights and architectural new builds. Vitrum Solutions supplies AND installs Korniche across Buckinghamshire, Berkshire, Oxfordshire, Surrey and Hampshire (never DIY).
Slim Ridge Specifications
Internal Ridge
Reduced-width ridge, hips and rafters
Construction
Thermally broken aluminium, gasket-sealed glazing
Thermal
Glass unit 1.2 W/m²K, 1.0 on Premium range (28mm argon double glazing)
Maximum Span
6 m × 4 m
Security
PAS 24 high security as standard
Why the Slim Ridge
Why the slim ridge matters
The internal ridge of a roof lantern is the visible structural beam running across the centre of the lantern from inside. On most aluminium roof lanterns this is wide enough to bisect the sky view from below. Korniche's reduced-width ridge keeps the view open: from a kitchen island or dining table looking up, the roof lantern reads as a near-uninterrupted glass plane rather than a structurally-divided rooflight.
Tapered structure, slender caps
The slim ridge comes from the structure itself. Korniche tapered the ridge, hips and rafters and made each element stronger and stiffer, so the visible frame is slimmer without losing rigidity. Narrow top and end caps finish the profiles outside, and custom seals encase every glass unit with no silicone inside the structure.
Thermal performance
Despite the slim ridge, Korniche keeps strong thermal performance. Thermally broken aluminium with a high-strength polymer insulating core and thermally isolated fasteners, and 28mm argon-filled double-glazed units with a warm edge spacer, giving a glass U-value of 1.2 W/m²K, or 1.0 W/m²K on the Premium range. Solar-control glass options available for south-facing extensions where heat gain matters.
Spans up to 6 m × 4 m
Made-to-measure for exact opening dimensions. Maximum spans up to 6m × 4m for large kitchen-extension and rear-elevation rooflights. Rectangular and pyramid lanterns at a fixed 25° pitch. Stock gloss white (RAL 9910), matt grey (RAL 7016) and matt black (RAL 9005), plus bespoke RAL and BS colours, with a different colour inside and out if you want one.
Vitrum supplies AND installs (never DIY)
Korniche is sold by some retailers as a self-fit kit. Vitrum Solutions does not supply Korniche on a self-fit basis — every Korniche we quote includes site survey, supply, professional installation by our own team (never subcontracted), structural sign-off where required, kerb formation, weather detailing and FENSA registration. Self-fit Korniche installations are responsible for the majority of leak-failure cases we get called to remediate; the cost saving on installation typically converts to a higher long-term remediation bill.
Korniche on Our Range
The slim-ridge spec is the system on the Korniche brand hub. The configurator handles size, glass options (clear, solar control, laminated or privacy, all self-cleaning) and external/internal RAL colour finish.
Get a free quote for Korniche Slim-Ridge Roof Lantern
Free no-obligation written quote. Fast response times. FENSA registered with a 10-year CPA insurance-backed guarantee. Serving Buckinghamshire, Berkshire, Oxfordshire, Surrey, Hampshire, Hertfordshire & West London.
Related Reading
Cost guide, planning guide, slim-vs-standard comparison and the independent Korniche review.
Roof Lantern Cost Guide UK 2026
What you'll actually pay — by size, glass spec and installation type.
Slim vs Standard Roof Lanterns
Is the premium slim-ridge upgrade worth it for your extension?
Planning Permission Guide
When permission is and isn't required for a roof lantern.
Our Korniche Review
What we rate, what to weigh up and who it suits.
Korniche Slim Ridge — Frequently Asked Questions
What does 'slim ridge' actually mean?
The internal ridge is the structural aluminium beam that runs across the centre of the roof lantern, visible from the inside looking up. On Korniche it is a reduced-width ridge. The visual difference from below is significant: a slim ridge reads as a thin line across the sky view, whereas a wide ridge reads as a structural divider that fragments the rooflight.
How does Korniche keep the ridge slim without losing rigidity?
Korniche tapered the ridge, hips and rafters and made each element stronger and stiffer than before, so the structure carries the load without an oversized ridge. Narrow top and end caps complete the slim look outside.
Does the slim ridge affect thermal performance?
No. The 28mm argon-filled double-glazed units have a glass U-value of 1.2 W/m²K, or 1.0 W/m²K on the Premium range, and the aluminium is fully thermally broken: a high-strength polymer insulating core runs through the entire structure and the fasteners are thermally isolated. Those details sit independently of the ridge width. Where heat gain matters, glass with higher solar heat reflection reduces solar gain.
How big can a Korniche roof lantern go?
Up to 6m × 4m maximum span as a single lantern. Most UK kitchen extensions sit comfortably within this range (typical opening 3m × 2m to 5m × 3m). Larger spans use multiple linked lanterns. Made-to-measure for exact opening dimensions in rectangular, square or custom aspect ratios.
Can I get any colour Korniche?
Yes. Korniche stocks gloss white (RAL 9910), matt grey (RAL 7016) and matt black (RAL 9005), with bespoke RAL and BS colours in a matt, gloss, satin or textured finish. A different colour inside and out is also available, so the lantern can match the elevation's window and door colours.
Do Korniche slim-ridge roof lanterns need planning permission?
In most cases no. If the lantern doesn't extend more than 150mm above the existing roof slope, it falls under permitted development. The Korniche system with its slim ridge sits well within the 150mm permitted-development limit (overall height above the roof is determined by the kerb height and the glazing pitch, not by the ridge). Listed buildings and conservation areas may need planning approval, and we can advise during the free survey. Full guide: /blog/do-roof-lanterns-need-planning-permission.
How does Korniche compare to other UK roof lanterns?
Korniche's reduced-width ridge, hips and rafters put more glass overhead than a conventional lantern. Its 28mm argon-filled units reach a glass-unit U-value of 1.2 W/m²K, or 1.0 on the Premium range. Custom seals encase every glass unit with no silicone inside the structure, and slender top caps finish the exterior. For premium kitchen extensions, loft conversions and rear-elevation rooflights where the aim is an uninterrupted view of the sky, Korniche is our first choice. Our full review is on the Korniche page: /korniche#korniche-review.
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