Frameless Flat Roof Skylight – Triple Glazed Glass Rooflight, 37 Sizes 300×300mm to 1500×3000mm

A dome rooflight lets light in. A frameless flat glass rooflight disappears — no visible frame, no curve to distort the sky, just a flush pane of glass sitting almost level with the roofline so that from below it reads as ceiling, not window. It's the specification people reach for on an extension or garden room where the rooflight itself is meant to be invisible from inside and barely there from above.

This is a genuinely triple-glazed, frameless flat rooflight — not a single-skin polycarbonate dome. The glass build-up is a reinforced 8mm toughened outer pane, a 6mm Low-E middle pane, and an 8mm toughened inner pane, with the cavities filled with argon gas for a U-value of 0.9 W/m²K — roughly on par with a good-quality window, far ahead of a basic polycarbonate dome. Self-cleaning glass and 39dB acoustic insulation come as standard, and every size carries UKCA certification and a 20-year structural warranty. The glass has a factory-built minimum fall across its span so water runs off even though the roof beneath is flat.

Where it's used

Specified where the ceiling view matters as much as the daylight — extensions, garden rooms, kitchen and living-space flat roofs, and any project where a visible dome or a chunky frame would look wrong from inside. It's a step up in both specification and price from a polycarbonate dome rooflight, and suits projects where thermal performance, acoustic insulation and appearance all matter, not just letting light in.

Sizes and specification

Available in 37 sizes from 300×300mm up to 1500×3000mm, covering everything from a small box rooflight to a large open-plan span. Every size shares the same construction — frameless, triple-glazed, argon-filled, 0.9 W/m²K U-value, self-cleaning coating, 39dB acoustic rating, UKCA certified, 20-year structural warranty — the only thing that changes between sizes is the glass dimension and weight. Larger sizes are heavy (the biggest units run to over 250kg) and are delivered kerbside on a pallet; plan access and lifting equipment accordingly.

Installation guidance

Fit onto a suitable insulated upstand or kerb sized to the unit's structural opening — see our OSB insulated upstand range for a ready-made kerb in matching sizes. Dress and bond the EPDM membrane up and over the kerb faces before the glass unit is lifted into place and fixed down per the manufacturer's fitting instructions. The built-in fall in the glass needs to run in the correct direction for drainage, so check orientation on site before final fixing. Given the weight of the larger sizes, plan for mechanical lifting rather than a manual lift on anything above roughly 1000×1500mm.

Ordering

Order to the structural opening size, not the visible glazed area, and always check against your kerb or upstand dimensions before confirming — these are made-to-size units and errors are costly to put right. Pair with our OSB insulated upstand range, EPDM membrane and contact adhesive to complete the installation. Need the roof area to be walked on, not just glazed over — a terrace or accessible balcony rather than a fixed skylight? This unit isn't rated for foot traffic; see our walk-on glass rooflight range instead.