Glass Roofs & Walk-on Glass

A structural glass roof replaces most or all of a roof with large glass units carried on glass beams, slim steel or aluminium supports. Side-return extensions often use a single run of glass from the house wall to the boundary, giving a bright kitchen without the ridge and bars of a framed roof lantern.

Overhead glass in a glass roof is generally specified with a laminated inner pane. If the inner glass breaks, the interlayer holds the fragments together instead of letting them fall into the room. BS 5516-2 is the British Standard code of practice for sloping and overhead glazing.

In England, Approved Document L sets a limiting U-value of 2.2 W/m²K for rooflights, calculated in the horizontal position. Frameless glass roofs and fixed rooflights are usually specified with low-E double or triple glazed units, and their declared performance should be checked against this before ordering.

In England, Approved Document L limits how much of an extension can be glazed when the simple standard route is used. Large glass roofs often go beyond that limit, so energy calculations are usually needed to show the extension still complies, and building control checks them.

Walk-on glass panels are laminated from several layers of toughened or heat-strengthened glass so the panel stays in place even if one layer breaks. The top layer usually carries an anti-slip finish, such as a fritted or etched pattern, and the panel thickness is calculated for the expected loads.

Glass floors and walk-on rooflights bring daylight into basements, lower floors and rooms beneath terraces. Each panel sits on a continuous, level support with gaskets or setting blocks so the glass never touches metal or masonry directly, and the structure below is checked by an engineer.

Fixed frameless rooflights sit on a flat roof upstand with the glass edge overhanging the kerb, so from inside you see only sky and plaster. The upstand must be level, insulated and weathered into the roof covering, and the roof needs a fall so water drains off the glass.

Glass roofs are heavy and the units are large, so installation often needs cranes, glass lifting robots or vacuum lifters, and sometimes road or pavement access arrangements. Access is planned at survey, because it can influence the maximum panel size and the installation day.

Overhead glass collects heat in summer. Solar-control coatings, low-E coatings and fritted patterns reduce heat and glare under south and west-facing roofs, while opening rooflights or vents elsewhere help warm air escape. Self-cleaning outer coatings reduce how often the glass needs washing.

The price of a glass roof or walk-on panel depends on glass size and make-up, the number of laminated layers, coatings, support beams or framing, structural design, lifting equipment and access. Bespoke shapes and very large panels cost more. See the guide prices for typical ranges.

A new glass roof or walk-on panel is building work that normally needs building regulations approval through building control, covering structure, energy performance and, close to a boundary, fire performance. Planning permission may also be needed depending on the extension and the property, so check with the council.

Glass roofs need regular cleaning from safe access, never by standing on non-walk-on glass. Silicone joints between panes should be inspected for splits, gutters and outlets kept clear, and any chips or scratches on walk-on panels checked, because the top layer is designed to protect the layers below.