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A custom skylight makes sense in exactly one situation: the light you want can’t be delivered by a standard-size unit. When that’s true, made-to-measure glazing is transformative. When it isn’t, it’s an expensive way to buy the same daylight — we covered that decision in Are custom rooflights worth the cost? This guide covers the what and how once you’re past the whether: types, materials, 2026 costs, and the rules.
The four families of custom skylight
1. Made-to-measure flat glass rooflights. The workhorse of modern extensions: a sealed glazed unit on an insulated upstand over a flat roof. Any size within engineering limits, fixed or opening, flush and minimal from inside. Most “custom skylight” projects are this.
2. Roof lanterns. A pitched glazed structure (usually aluminium-framed) that sits proud of a flat roof, adding height and drama over kitchens and dining spaces. Sized semi-custom by most suppliers — you specify dimensions, they assemble from a system.
3. Walk-on and structural glazing. Glass you can stand on — roof terraces, floor lights over basements. Thick laminated build-ups, engineered support, and priced accordingly. Genuinely bespoke engineering, not a catalogue product.
4. Bespoke pitched-roof glazing. Non-standard shapes and sizes for pitched roofs — heritage renovations, vaulted spaces, conservation profiles. This is the smallest category because standard roof windows in combi arrangements cover most pitched-roof ambitions for far less.
What they cost in 2026
Per Toughened Glass Systems’ price guide and MyJobQuote’s lantern data:
| Type | Supply | Fitted (typical) |
|---|---|---|
| Made-to-measure flat glass (small–medium) | £1,000–£4,000 | +£1,000–£2,500 install |
| Roof lantern (small–medium) | £1,000–£4,000 | £2,000–£5,000+ total |
| Large / walk-on / structural | £8,000+ | project-priced |
| Standard-size comparison | £330–£1,500 | £900–£2,600 |
Glazing spec moves these numbers more than size: triple glazing, solar-control coatings, self-cleaning glass and electric opening each add hundreds to thousands.
Materials: an honest comparison
Glass is the answer for living spaces — the clarity, the acoustics in rain, the coatings (self-cleaning, solar control), and a multi-decade lifespan. Specify toughened outer and laminated inner panes as a minimum for overhead glazing; reputable suppliers won’t sell you less.
Polycarbonate is lighter, cheaper and near-unbreakable, but scratches, hazes with UV over time, and sounds like a drum in rain. Right for garages, workshops and commercial roofs; wrong above a kitchen table.
Acrylic sits between — clearer than polycarbonate, cheaper than glass — and mostly appears in budget dome rooflights. Fine for outbuildings; in a home you’ll wish you’d bought glass.
Design decisions that matter more than shape
- Orientation. North-facing roof glazing gives soft, even, glare-free light all day — the architect’s choice for kitchens and studios. South-facing maximises light and winter warmth but needs solar-control glazing or you’re building a greenhouse; overheating is the most common regret in glazed extensions.
- Ventilation. Big glazed areas trap summer heat. At least one opening unit (or an opening roof window elsewhere in the room) makes the space livable in July.
- Upstand and finish. On flat roofs, the upstand detail decides whether the skylight looks built-in or bolted-on — and whether it leaks. Insist on an insulated upstand and a proper waterproofing tie-in.
- Access for cleaning. Fixed glazing you can’t reach needs self-cleaning coating or a window cleaner with poles. Decide before, not after.
Rules and regulations
Same regime as any skylight: planning permission usually isn’t required provided the glazing projects no more than 150mm from the roof plane (lanterns on flat roofs generally qualify; conservation areas and listed buildings need checking). Building regulations always apply — structural adequacy for the opening, Part L thermal performance for the glazing — and oversized or walk-on glazing needs engineer’s calculations. Use installers who handle building control sign-off as part of the job.
Getting it built
Buy the glass and the installation as one contract where possible — split responsibility is how leaks become nobody’s fault. Ask suppliers for: the glass spec in writing (build-up, coatings, U-value), the upstand/flashing detail, engineering calcs for anything oversized, and references from projects of similar scale. And before signing anything bespoke, price the standard-size alternative one more time — the brands’ catalogue ranges are wider than most people realise.
Frequently asked questions
What types of custom skylight are there?
Four main families: made-to-measure flat glass rooflights (the most common), roof lanterns (pitched glazed structures for flat roofs), walk-on structural glazing (terraces and floor lights), and bespoke pitched-roof glazing for non-standard openings in existing roofs.
How much does a custom skylight cost in the UK?
£1,000–£4,000 supplied for small-to-medium made-to-measure flat glass units in 2026; large or structural glazing £8,000+; installation typically adds £1,000–£2,500. Standard-size units cost a fraction of that — always price them first.
Should I choose glass or polycarbonate for a skylight?
Glass for houses: better clarity, acoustics, longevity and self-cleaning coatings. Polycarbonate is lighter, cheaper and tougher — the right call for garages, outbuildings and commercial roofs, but its optical quality and lifespan don't suit living spaces.
Do custom skylights add value to a home?
A light-filled extension shows and sells better, but no credible UK data supports a specific percentage uplift from skylights — treat any such figure with suspicion. Buy for the living benefit, not a promised return.
Keep reading
Bespoke rooflights cost £1,000–£4,000+ supplied versus a few hundred for standard sizes. When made-to-measure is worth it — and when it isn't.
Most UK skylight installations cost £900–£2,500 per window in 2026, fully fitted. Full breakdown: supply, labour, scaffolding, flat roofs and lanterns.
Fakro, Keylite, RoofLITE+, Roto and Dakea compared against VELUX on 2026 prices, guarantees and quality — and which alternative fits which job.