The short answer
Usually, yes. Forming a fresh opening through a roof or a floor counts as building work, so the structure around the glass, the heat loss through the unit and any open edge beside it all fall under the Building Regulations. Swapping an old walk-on unit for a new one still has to meet the thermal limit for a rooflight. The council or a registered building control approver inspects; we handle the Building Control notification where the work is notifiable, and planning is a separate question.
- Free survey, fixed written quote
- 10-year workmanship guarantee
Structure comes first
A glass floor that people stand on loads whatever is beneath the frame, so the first thing a building control officer asks about is the support. A joist cut to make room for the opening has to be replaced by trimmers or a beam that carries the weight round the gap and into the walls. A concrete slab with an opening cut through it needs the edges and reinforcement considered. On a flat roof used as a terrace, the deck, the joists and the bearings at the wall all get checked together.
We record what exists at the survey, pass the span and the use to the glass manufacturer and, where the structure is changing, to an engineer for a calculation. Any strengthening appears as a line on the written quote. The fuller picture of glass loads is on our page about walk-on glass load ratings.
Energy limit for the glass
Part L of the Building Regulations covers fuel and power conservation. For an existing dwelling, Approved Document L, Table 4.2, sets 2.2 W/m²K for a rooflight and 1.4 W/m²K (or Window Energy Rating band B) for a roof window, measured for the whole unit with its frame. A walk-on unit set into a terrace, a paved roof or a slab is normally assessed against the rooflight limit, and we confirm the category at survey. The sealed double glazing, the coating and the thermally broken frame are chosen to reach the limit, and the figure goes onto your quote.
A replacement counts too. When an old walk-on panel with failed seals is swapped, the new unit has to meet the same limit as a new opening would. Our guide to rooflight U-values sets out how the number is worked out.
| Part of the job | What is looked at |
|---|---|
| Trimmers, beams and bearings | Structure under the opening |
| Glass, frame and seals | Heat loss, using the rooflight limit |
| Open edge beside a terrace unit or lightwell | Guarding against a fall |
| Roof covering near a boundary | Resistance to fire spread from outside |
Edges, drops and neighbours
Where a unit sits next to a drop, Approved Document K, which covers protection from falling, applies to the edge. A glass panel by a stair opening, a lightwell with an open side or a terrace edge may call for a guard, and we raise that while we measure. The glass is not meant to be the only protection between a person and a fall unless it has been designed for that role.
Roofs have a fire rule of their own. Approved Document B covers how the covering performs against fire spreading from a nearby building, and a terrace close to a boundary can change what is acceptable. We read the distances on site.
Who does what, and the planning side
The Building Control notification is ours to make where the work is notifiable. A building control officer at the council, or a registered building control approver, which is the title a private inspector has held since April 2024, then looks at the work and signs it off. Keep the completion paperwork with the deeds, because a future buyer's solicitor tends to ask for it.
Planning permission is a different route. A rooflight in a roof is judged against permitted development Class C, and a flat or maisonette has no householder rights. Being in a conservation area does not by itself remove Class C; only an Article 4 direction does. A terrace with a balustrade is a wider question than the glass alone, so check the position in our skylight planning permission guide and the general skylight Building Regulations guide. The hub page for walk-on rooflights shows how the rest of the job fits.
Starting the paperwork with a survey
Send a photo of the room, a note of what stands above it and the age of the house through the quote form. At the free survey we look at the structure, the surface and the edges, and the fixed written quote lists the structural work, the glass and the notification, with a 10-year workmanship guarantee in writing.
