Flagship guide · 9 min read
What Affects the Cost of Premium Glazing
Two homes with the same number of windows can end up on very different invoices. Here is what genuinely moves the price, and what does not.
Rooflight Cost Guide
A standard fixed flat rooflight typically costs £1,200–£4,000 supplied, with large walk-on or sliding rooflights costing considerably more.
3 min read
Rooflights bring a disproportionate amount of daylight into a room for their size, which is exactly why they have become a staple of extension design over the last decade. Cost varies enormously though, from a modest fixed unit over a hallway to a vast sliding or walk-on rooflight over a kitchen extension, so it is worth understanding where your project sits before budgeting.
As a guide, a standard fixed flat rooflight typically costs £1,200–£4,000 supplied, before installation. Larger, walk-on or sliding units cost considerably more, and installation, upstand and weathering detail need to be budgeted separately from the unit itself.
Types and where they sit on price
| Type | Typical use | Price position |
|---|---|---|
| Fixed flat rooflight, standard size | Hallways, bathrooms, small extensions | £1,200–£4,000 supplied |
| Fixed flat rooflight, large format | Kitchen extensions, open-plan living | Above standard range |
| Opening/vented rooflight | Ventilation, means of escape | Above fixed equivalent |
| Walk-on rooflight | Roof terraces, basement light wells | Considerably more than fixed |
| Sliding/electric rooflight | Feature openings, courtyards | Considerably more than fixed |
The jump in price for larger formats is not linear. A rooflight roughly double the standard size is not simply double the price, because larger spans of glass require thicker units, more robust upstand construction and more careful handling during installation.
What affects the price beyond size
- Glazing specification, including solar control coatings to manage overheating under a rooflight
- Opening mechanism, whether manual vent, electric opening for ventilation, or fixed only
- Upstand construction, whether built by the roofing contractor or supplied as a kit with the rooflight
- Frame finish, particularly slim-profile frameless-look units versus visible frame systems
- Access for installation, particularly on steep or high roofs
Installation and the upstand
The rooflight unit itself is only part of the cost. The upstand, which is the raised timber or insulated kerb the rooflight sits on, needs to be built to the correct height and properly insulated and weathered, usually by the roofing or building contractor rather than the glazing supplier. Clarifying who is responsible for the upstand and the roofing detail around it avoids a gap between trades, similar to structural openings for sliding doors.
Budgeting for a rooflight
For a single-storey extension with one or two standard fixed rooflights, budgeting £1,200–£4,000 per unit supplied, plus separate installation and building costs, is a sensible starting point. For a large open-plan extension with a feature sliding or walk-on rooflight, it is worth treating that item as its own budget line within the wider project and discussing it directly with your rooflight supplier at design stage.
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