Most people who ask what walk-on glass costs are really asking two things at once. They want a rough sense of whether the idea is within reach, and they want to know what could make it more expensive than they think. The first question cannot be answered honestly without seeing the house. The second can be answered here.
A walk-on rooflight is a made-to-order piece of structural glass, set into a floor, a terrace or a patch of paving, with the opening around it built to carry the load. The glass is one part of the bill. The opening, the steel or timber that supports it, the way the surface is finished and the way the glass reaches the room all add their own lines. Once you know what each line pays for, a quote stops being a single frightening number.
Why there is no price list
A standard roof window comes in a set of sizes, and a price follows each size. Walk-on glass does not work that way. Each unit is cut and built up to fit one opening and to carry one set of loads. Two panes that look the same from above can differ underneath in the number of layers, the interlayer, the coatings and the edge detail.
The structure matters just as much. Glass in a timber landing needs trimmers and a lining. Glass in a concrete yard slab needs the slab cut cleanly and a support let into it. Glass in a roof terrace needs a waterproof upstand and falls. Those are different jobs with different labour, so a figure quoted over the phone for one would be wrong for another.
Size and span of the glass
Size is the first driver, and it does not behave in a straight line. Glass flexes a little under load, and the longer the span, the more it flexes. To keep that movement small, a larger pane needs more layers or thicker layers, and the cost rises faster than the area does. A pane just big enough to light a stairwell is a modest item. A pane that spans most of a terrace is a different order of expense.
Shape counts too. A square or a slim rectangle is straightforward. Angled corners, a curved edge or a pane that has to fit around a column cost more to cut and toughen. Where the opening is large enough that the glass is made in two or more sections, there is a joint to detail and seal, and each section has to be lifted in separately.
It is worth asking whether the opening needs to be as big as first imagined. A modest increase in size can lift the price of the glass and the structure together, while a slightly smaller pane can still bring a surprising amount of daylight into a room below. Our guide to walk-on glass thickness explains why span and build-up travel together.
The load the glass must carry
A landing that is crossed by the household is asked to do less than a terrace with a table, four chairs and a heavy planter. A courtyard that might see a delivery trolley is different again. The heavier the use, the more substantial the build-up, and the more it costs.
This is the most useful thing you can tell us at the survey. Be honest about the heaviest realistic use, including the occasional party, and the glass is specified for that. Specifying too lightly to save money is the one economy that cannot be undone later without replacing the pane. Our explanation of walk-on glass loading sets out how the numbers are arrived at.
What to tell us about the load
- Who will walk on it, and how often
- Whether furniture will stand on it, and how heavy the pieces are
- Whether anything might be dropped, dragged or wheeled across it
- Whether it is inside, outside, or under a terrace surface
Cutting the opening and carrying the structure
In many houses this is the largest line after the glass, and sometimes larger. Removing a section of floor or roof takes out timber, steel or concrete that was carrying weight, and that weight has to be taken round the opening. In a timber floor, that is doubled joists and hangers. In a slab it can be a steel frame set into the edges of the cut. Where the opening is wide, a structural engineer draws the support and we build to the drawing. The engineer's fee is a line of its own on the quote.
The ease of the cut changes the price. An opening that sits neatly between two joists is far quicker than one that crosses three. An opening that lands over a wall or a beam may need that member moved or reinforced. A cellar with a brick vault overhead, as many Victorian terraces have, calls for slower, more careful cutting than a plain timber floor.
| Timber floor, opening between joists | Lighter trimming, fewer hours |
|---|---|
| Timber floor, opening across joists | Doubled members and hangers |
| Concrete slab | Cutting equipment, a support let into the slab |
| Brick vault or arch | Slow, careful cutting and temporary support |
| Flat roof terrace | Upstand, falls and waterproofing as well |
Getting the glass to the room
Walk-on glass is heavy. A pane of useful size is more than one person can carry, and it has to travel from the vehicle to the opening without being knocked. Where it can be lifted in from outside across open ground, the lift is straightforward. Where it has to go through a front door, down a hall and round a turn, more people are needed and the route has to be protected along the way.
When access is tight, a scaffold, a tower or a small lifting aid may be needed, and it appears as a separate line so you can see what it adds. Covering the floors, stairs and furniture along that route is simply how we work, so it sits inside every quote and not on top of it.
Finish, drainage and the surface around the glass
The glass sits in a frame, and the frame sits in a surface: paving, decking, a screed, a timber floor or a roof covering. How that surface is brought up to the glass is where a good job shows. Flush stone paving needs cutting to a neat joint. A roof terrace needs a drained, waterproof edge. An internal floor needs a trim that is comfortable underfoot.
The anti-slip finish on the walking face is another choice. Fired dots and acid-etched surfaces both give grip, and the price differs a little between them and between patterns. Our page on whether walk-on rooflights are slippery compares them.
The room below has its own finish. A lined soffit, a plastered reveal and any lighting set into it are listed separately. If you plan to decorate the room yourself, tell us and the line can be left out.
Where the glass faces outdoors or sits over a room that is lived in
Glass that forms part of the building envelope has to keep heat in as well as carry weight. That means a sealed unit under the walking layers, with a low-emissivity coating and a gas-filled gap. It costs more than a single laminated floor panel, and it is the right choice wherever the room below is heated or the glass faces open air. A fully internal pane between two heated spaces, such as a landing over a hall, does not need the thermal layer, and the quote reflects that.
Because an external pane is also a roof or a terrace, the insulation around it, the upstand and the drainage all become part of the cost. They are the things that stop the glass being a cold, damp spot in the room. Read more in our page on insulated walk-on rooflights.
Planning and Building Regulations fees
Some of the cost is paperwork. Cutting a new opening brings Building Regulations into play for the structure and the thermal performance, and that carries a fee. We arrange the notification where the work is notifiable, and the fee is shown on the quote.
Planning is a separate question and depends on the building. Flats, listed buildings and homes in some conservation areas have different rules, and a council can charge for an application. Our planning permission and Building Regulations guide sets out when each applies. The council confirms the position for your street, and where an application is needed, its fee is added as its own line.
Options that are worth pricing separately
Some choices are best seen as options rather than part of the base figure, because they change the result without changing the structure. A fritted or frosted interlayer for privacy is one. A second pane in the same room, a different surface pattern, and lighting set into the reveal below are others. Asking for each to be priced on its own line lets you weigh the extra against what it gives.
The same goes for sequencing. If the room below is going to be redecorated, doing the glass first and the decoration afterwards saves finishing the same ceiling twice. Say so at the survey and the day plan can be built around it.
Reading the written quote
A quote for walk-on glass should let you hold each cost up against the work it describes. Once the free survey is done, our quote arrives in writing, itemised so that every cost stands alone, with a plan for each day of the fit. These are the lines to look for.
- The glass unit, with its build-up and finish
- The frame and its fixings
- Forming the opening, including trimming and supports
- Any engineer's design and checking
- Access, lifting and protection of the route
- The surround or the roof detail
- Lining and finishing the room below
- Building Control, and planning where it applies
- Clearing away and taking the waste
If you collect more than one quote, set them side by side and look at the gaps. A lower total often means a missing line: no engineer, a lighter build-up, or no finishing below. For the way our broader quotes are laid out, see the costs overview, or the wider guide to what a skylight costs to fit in York.
Getting a figure you can rely on
The most useful step is the survey. We look at the floor or the slab from both sides, measure the opening, ask about the use and note the way the glass will arrive. The visit costs nothing, and the quote that follows is yours to keep whether or not you go ahead.
When you are ready, the form below is the quickest way to ask. If you want to read around the subject first, our main walk-on rooflight installation page covers the glass, the structure and the handover in more detail.