Anti-slip glass for walk-on rooflights

Float glass has an almost perfect surface, which is exactly the problem. There is nothing for the sole of a shoe to key into. Rain, condensation, a spilled drink or a damp footprint turns it into something close to ice, and in a position like a terrace or a back step the glass is damp for much of the year.

The top sheet of a walk-on panel is also the wearing surface. Grit carried in on shoes scratches it, and over years that scratching dulls clear glass and changes how it holds water. A surface treatment is part of how the panel stays safe as it ages, not only how it feels on day one.

Glass in floors is not covered by the rule most people know about glazing and safety. Part K of the Building Regulations deals with glazing in critical locations such as doors and low level panels, and it does not set out a slip resistance for a walk-on rooflight. The specification comes from structural guidance for glazed floors and from the supplier's own tested products, which is why asking for the test data matters. Both belong in the quote.

There are four routes, and a panel can combine more than one. Each describes the finish on the upper face of the top sheet.

Ceramic frit

A ceramic enamel is printed onto the glass in a pattern, usually dots or lines, and fired in the toughening furnace so it fuses to the surface. The enamel stands slightly proud and gives a firm bite for a shoe. It is the most durable of the treatments, because it is part of the glass, and it comes in many patterns and densities, including white, grey and tinted.

Acid etching

The surface is treated with acid so that it forms a fine, even, matt texture across the whole sheet. It has a soft, frosted look, hides fingerprints and scuffs well, and gives a gentle grip. A heavier etch grips more and is slightly harder to wipe clean.

Sandblasting

The glass is blasted with fine abrasive to roughen the surface, usually in a pattern or a band. It can give good grip, and it is the choice when a design is wanted, such as a border. Because it removes a little glass, it is done carefully on structural sheets, and the supplier controls the depth.

Textured or printed surfaces

A rolled pattern or a printed coating adds relief to the surface. These can be economical, but a coating applied after manufacture is only as lasting as its bond, so ask whether it is fired into the glass or stuck onto it.

Stick-on anti-slip strips and paint-on coatings exist too. They are used to retrofit old glass, and they wear, peel and catch dirt faster than the treatments above. On a new panel, the grip should be part of the glass.

No single finish wins on every row. Frit gives the firmest grip outdoors. Etching gives the calmest appearance indoors. A sandblasted band can mark out where to step. The right one is the one that fits the position.

Grip can be tested. The method used for floors in the UK is the pendulum test, in which a rubber slider on a swinging arm is drawn across the wetted surface and the drag on it is read off as a pendulum test value. Higher values mean more grip, and the figure is taken in both dry and wet conditions. Manufacturers of treated glass publish results for their own patterns, and a good supplier will give you the figure for the pattern you are being offered.

The number is a guide, not a promise. It depends on the surface being clean, on the footwear, and on what is lying on the glass. A finish that scores well when new can lose some grip if it clogs with algae or polishes under years of traffic. For that reason, think of slip resistance as a property of the glass plus its upkeep.

Ask three things of any quote: which treatment is on the top face, what slip test result is held for that pattern, and whether the treatment is fused into the glass or applied after. If the answers are vague, the grip is probably left to chance.

People tend to think of grip as a single property, but it changes with conditions. A frit pattern that feels secure under a rubber sole may feel sharp under a bare foot, and a fine etch that is comfortable in socks can offer less to a wet leather sole. Ice and frost are a separate case again, because a thin film of frozen water fills the texture and a treated surface stops helping until it is cleared.

That is why the test conditions matter when you read a slip result. Ask whether the figure was taken wet, with what slider, and on a clean sample. A pattern that is tested wet with a rubber slider tells you about wet shoes. It tells you less about bare feet in a bathroom, where soap and skin oils change the result.

Gradient plays a part as well, and so does the direction of travel. A terrace panel is usually near flat, with only a shallow fall. If the glass sits on a ramp, a stair or a sloping area, the finish needs to be firmer, and the slope should be part of the conversation at survey.

Where the panel is decides how demanding the surface has to be.

A panel in a terrace or patio meets rain, leaves, frost and shade, and a fused frit pattern is the sensible default. The detail on a deck is covered in our guide to walk-on rooflights for roof terraces and balconies. A panel at a threshold, just outside a door, is the one that gets wet feet most often, and deserves the firmest pattern on the terrace.

Over a cellar or in a courtyard, the glass sits at ground level, and the surrounding paving drains water towards it. Frit or a deep etch both do well, and the panel needs a detail that stops grit collecting at its edges. Georgian and Regency terraces in Southernhay and St Leonards, and older streets in Topsham and Exmouth, often have cellars under front areas where this arrangement is possible.

Indoors, where a glass floor panel or landing light is walked on in socks or bare feet, grip matters in a different way. A hard frit pattern can feel rough, so a light etch is usually more comfortable. In a bathroom, kitchen or hallway where water meets the glass, step up to a finish with a tested wet grip.

Think too about who will use it. Children, older relatives and pets all behave differently on glass. Our answer on whether a walk-on rooflight is safe for children covers what changes with young feet.

Every anti-slip treatment takes something away from a perfectly clear panel. A dense frit pattern blocks part of the light where it sits, and a heavy etch scatters it. The loss is rarely a problem, because the panel is lighting a room and nobody is looking out through it, and diffused light is gentle. Still, you can choose how much light you give up.

A sparse pattern of small dots lets most of the light pass and still holds a shoe. A close pattern grips more and shades more. If daylight into the room below is the reason for the panel, pick the lightest pattern that meets the grip needed in that position, and ask for a sample you can look at against the sky.

The pattern is seen from beneath as well. A frit appears as a scatter of shadows when the sun is out and as a faint grid in dull weather. An etch looks like a softly frosted ceiling light. A sandblasted band reads as a border. All of these also give some privacy from the room below, because feet and furniture legs soften into shapes. If the room is a bedroom or bathroom, it is worth choosing with that in mind.

Treated glass keeps its grip when it is kept clean. Dirt, moss and algae fill the texture and make it slick, and that is the main way a good finish loses its value.

• Brush the surface regularly with a soft brush and warm water, and rinse with clean water.
• Use a mild cleaner of the kind the glass supplier recommends, and avoid abrasive powders and wire brushes.
• Keep pressure washers away from the edge seals.
• Clear leaves and moss from the surround, because the glass is damp wherever they gather.
• Look for polishing in the places most walked on, which can be the first sign that the surface is wearing.

The top sheet of a walk-on panel is designed to be replaceable. It is a sacrificial layer on top of the structural laminate, so if the surface is scratched or worn smooth after many years, the top sheet can be replaced without removing the whole unit. Whether that is easy depends on how the frame and the surrounding deck were built, which is worth asking about at the quote. We go through the layers in walk-on rooflight glass specification.

A treated panel changes how the room below looks, and so does everything else around it. The glass is a few centimetres thick, the frame sits on or in the structure, and between the frame and your ceiling there is a lining that you will look at every day. In a floor or flat roof that lining is a short shaft, finished in plaster or board, with beads and a paint line at each edge.

That finish is part of the job, and it goes down in the finish schedule that accompanies each Brightview quote. On a walk-on panel that document covers the room, what the ceiling and the roof or floor are built from, the shape of the lining, and the final surface, either primed for you to decorate or already painted. The glass specification is listed in the same place, so the anti-slip treatment you picked is recorded beside the plaster and the trim. Ask to see a sample of the etched or fritted finish in daylight before you choose, because the look changes noticeably between a bright window and a dim stairwell. Our guide to how a rooflight is finished inside explains the layers in the order they go in.

Anti-slip glass is only one decision in the whole build. The structure, the waterproofing, the glass and the finish all need to agree. You can read how we handle each of them on our walk-on rooflight installation page, and if you would like a panel specified for your own house, ask for a quote and we will arrange a survey.