Supplied AND Installed · FENSA Registered
Korniche Slim Ridge
The 40mm internal ridge — slimmest on the UK market — is Korniche's defining engineering feature. Other UK aluminium roof lanterns have 60-80mm internal ridges that visibly bisect the sky view from below. Korniche's slim ridge keeps the rooflight reading as a near-uninterrupted glass plane. Combined with patented snap-fit glazing, thermally broken aluminium and U-values from 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
40 mm — slimmest on UK market
Construction
Thermally broken aluminium, snap-fit glazing
Thermal
U-value from 1.2 W/m²K (argon-filled double glazing)
Maximum Span
6 m × 4 m
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 60-80mm wide — visually substantial enough to bisect the sky view from below. Korniche's 40mm internal ridge is the slimmest on the UK market: 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.
Patented snap-fit glazing
The slim ridge is possible because Korniche uses a patented snap-fit glazing system rather than the silicone-bedded or capped glazing found on competitor brands. The structural strength comes from the engineered profile geometry rather than from over-sized capping or bracing — so the visible interior frame can be slimmer without compromising rigidity or weather sealing. Side benefits: faster installation, no external capping, no visible fixings, no silicone mess to age and discolour.
Class-leading thermal performance
Despite the slim ridge, Korniche maintains class-leading thermal performance. Thermally broken aluminium frame, polyamide thermal break, argon-filled double glazing as standard delivers whole-product U-values from 1.2 W/m²K. Triple-glazed and solar-control glass options available for shaded sites or south-facing extensions where heat gain matters. Comfortably exceeds Approved Document L thermal demand.
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, square and custom aspect ratios. Any RAL colour powder-coat externally with white or anthracite internal finish.
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 Korniche slim-ridge spec is the system on the Korniche Roof Lanterns product page. The configurator handles size, glass options (clear / solar control / Pilkington Activ 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.
Korniche Independent Review
Is Korniche the best on the market? Independent assessment.
Korniche Slim Ridge — Frequently Asked Questions
What does '40mm internal 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 most UK aluminium roof lanterns the internal ridge is 60-80mm wide. On Korniche it's 40mm — the slimmest on the UK market. The visual difference from below is significant: a 40mm ridge reads as a thin line bisecting the sky view, whereas a 70mm+ ridge reads as a structural divider that visibly fragments the rooflight.
How does Korniche keep the ridge slim without losing rigidity?
The slim ridge is possible because Korniche uses a patented snap-fit glazing system rather than silicone-bedded or capped glazing. The structural strength comes from the engineered profile geometry — the way the aluminium extrusions interlock — rather than from over-sized capping or bracing. This is the key engineering innovation that distinguishes Korniche from competitor aluminium roof lanterns.
Does the slim ridge affect thermal performance?
No. Whole-product U-value is from 1.2 W/m²K with argon-filled double glazing — class-leading among aluminium roof lanterns and comfortably exceeding Approved Document L thermal demand. The thermally broken aluminium frame plus the polyamide thermal break sit independently of the ridge slimness — they're separate engineering details. Triple-glazed and solar-control upgrades are available where extra performance is wanted.
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 — any RAL Classic colour for the external powder-coat finish, with a choice of white or anthracite for the internal finish (or matched RAL inside if specified). Most-specified externals: Anthracite Grey (RAL 7016), Black (RAL 9005), White (RAL 9010) — matching the elevation's window/door colour scheme.
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 40mm 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 — 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 40mm internal ridge is the slimmest on the UK market — most alternatives are 60-80mm. Thermal performance (U-value from 1.2 W/m²K) is also significantly better than budget aluminium lanterns (typical 1.6-1.8 W/m²K). Snap-fit installation is faster and more weatherproof than silicone-sealed systems and there's no external capping to age. For premium kitchen extensions, loft conversions and rear-elevation rooflights where the architectural intent is uninterrupted sky view, Korniche is the default UK choice. Independent review: /blog/korniche-roof-lantern-review.
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