How much does a walk-on rooflight cost?

On a walk-on unit, size changes more than the area of glass. A larger pane calls for heavier glass, a stronger frame and a support able to take the extra weight, and each of those is part of the price. Outline matters a little: a plain rectangle is simpler to make than a bespoke shape. Walk-on units for homes are generally made to suit the opening we survey, rather than picked from stock sizes.

The pane is laminated glass, and the maker chooses the build-up for the load and the span. More sheets, thicker sheets and a stiffer interlayer all change it. For a heated room underneath, the pane can also form part of a sealed unit, and triple glazing changes both the build and the load the support carries. Solar control coatings, which some makers offer for sunny terraces, are a further choice. The guide to glass and load figures explains what each layer is for.

The class is picked according to what the surface will carry. A terrace set with a table, chairs and planters needs a higher class than a path to the back door, and a surface that takes a crowd needs a higher one again. A higher class means a heavier build, so describe the real use at the survey and let the specification follow it, not a guess at a class.

Each maker prices its finishes in its own way, and a pattern over the whole pane differs from one over part of it. On an outdoor surface that gets wet, a finish with grip belongs in the specification rather than on a list of extras. How the options behave when wet is covered in its own answer.

This is where two jobs with the same pane can differ. A pane laid on a firm slab with a sound upstand needs little around it. One going into an existing flat roof or balcony may need joists trimmed and strengthened, an upstand formed and the terrace waterproofing lapped into the frame. A new opening also brings in the building control body.

Where the work is notifiable, we handle the Building Regulations notification with the council's building control team or a registered building control approver. Rules for the glass itself are covered in the answer on the Building Regulations side.

A laminated pane is large and heavy, and getting it to a terrace can mean a lifting device or a route through the house. Inside, the ceiling opening beneath gets lined and finished. A blind for the room is a choice of its own, sized to the opening and chosen to suit the frame, as is any electric control.

A replacement starts from what is already there. The label and the measured size of the old pane tell us what the new one must fit, and a support that is sound and level keeps the work simple. Where the opening or the frame bearing has to change, the price changes with it. A cracked or misted pane is a replacement job, and the survey is where we find out whether the opening can be reused as it stands or needs altering. A like-for-like swap of a whole rooflight is still a controlled fitting.

A photo shows the terrace but not the structure, the fall or the room beneath, so no figure comes from one. No charge is made for the survey, which comes first: the opening and its support are measured, we ask how the surface will be used and the room below gets a look too. A photo of the room and the terrace can be sent to WhatsApp 07880 284133 to start things off, though no price comes from it. A fixed written quote follows the visit. Setting the panel into its frame counts as fitting, and so the 10-year workmanship guarantee reaches it too.

When you compare quotes from other firms, make sure each describes the same job. For every type side by side, see the costs overview. The product itself is described on the main walk-on page.