When it comes to installing a roof lantern, getting your measurements right the first time is absolutely essential. The Korniche Roof Lantern is one of the most advanced and precision-engineered products on the market – which means accuracy matters. Measuring correctly ensures a perfect fit, a watertight installation, and the stunning slimline finish that Korniche is known for.
At The Rooflight Centre, we’ve created this practical measurement guide to help both homeowners and installers achieve the best results with Korniche roof lanterns. Follow the steps below to make sure your lantern fits seamlessly and performs exactly as designed.
Explore our full range of Flat Roof Windows and Korniche roof lanterns today.
Why Accurate Measurement Matters
Unlike standard glazing, Korniche roof lanterns are built with precision-engineered aluminium profiles and tight tolerances. This ensures a sleek, minimal frame and exceptional strength, but it also means there’s little room for error. Even a few millimetres off can affect alignment, weatherproofing, and thermal performance.
By following the correct measuring process, you’ll achieve:
– A perfect watertight seal between lantern and upstand
– Improved energy efficiency and insulation
– Easier installation with no on-site adjustments
– A clean, professional finish that looks great inside and out
Understanding Korniche Roof Lantern Dimensions
Before you start measuring, it’s important to understand how Korniche defines its sizes. Korniche measurements are based on the external upstand dimensions – the outside edge of the timber upstand on which the lantern will sit.
Key terms to know:
– Upstand Size – the timber or insulated frame built into the roof to support the lantern. – Overhang – how far the lantern extends beyond the upstand edge for water drainage. – Lantern Size – the external measurement including the overhang.
– Structural Opening Size – the hole cut in your roof before fitting the upstand.
Step 1: Measuring Your Upstand
Your upstand is the foundation of your roof lantern installation. The Korniche system is designed to sit on a timber upstand that’s at least 70mm wide and 150mm high.
Recommended:
– Width: Minimum 70mm
– Height: Minimum 150mm
Ensure the top of the upstand is flat, level, and square. The outer measurement of your upstand determines the lantern size to order.
Step 2: Allow for Overhang
Your Korniche roof lantern should overhang the upstand by 6mm per side (12mm total). This allows for water drainage and prevents pooling between the frame and the membrane.
Step 3: Calculating Lantern Size
Add 12mm to the total upstand size (6mm per side) to get the correct lantern size.
Example:
– Upstand external size: 1988mm x 988mm
– Add overhang (12mm total): +12mm
– Lantern size: 2000mm x 1000mm
Step 4: Determining Roof Opening Size
If building your roof from scratch, reduce your opening size by 140mm in both directions (70mm each side).
Example:
– Lantern size: 2000mm x 1000mm
– Upstand width: 70mm (140mm total)
– Opening size: 1848mm x 848mm
Common Measurement Mistakes to Avoid
– Measuring internal instead of external upstand size
– Forgetting the 6mm per side overhang
– Incorrect upstand height
– Ignoring insulation and roof build-up
– Assuming “nominal size” equals “hole size”
Why Choose The Rooflight Centre?
At The Rooflight Centre (RLC), we’re more than just an online retailer – we’re the e-commerce division of Lonsdale Metal Company (LMC), a fourth-generation family business founded in 1954. Our products have featured in Buckingham Palace, The British Museum, and 10 Downing Street, trusted by architects and homeowners alike.
We’re proud to make premium quality rooflights available to every customer, offering:
– High-performance rooflights
– Fair pricing without compromise
– Fast delivery and easy online ordering
– Dedicated, expert support from our team
Ready to Order Your Korniche Roof Lantern?
Measure accurately, install confidently, and achieve stunning results. Explore our full range of Flat Roof Windows and Korniche Roof Lanterns today. By choosing The Rooflight Centre, you’re investing in accuracy, reliability, and a brighter home.
