Do walk-on rooflights scratch?

What causes marks

Dragged furniture. The main culprit. Grit trapped under a chair or table foot dragged across the panel acts as an abrasive. Lift rather than drag.

Dropped tools during later building work. Point impact is far more likely to damage a panel than any amount of walking on it.

Scaffold or props bearing on the glass. Never acceptable, and it happens more often than it should.

The anti slip surface

The frit is a ceramic ink fired into the glass during toughening, so it is part of the glass rather than a coating on it. It does not wear off, peel or scratch away.

A panel in daily use for twenty years still has its slip resistance, which is the important part.

What it does do

The textured surface holds a little dirt in the pattern, which is the trade for grip. Regular cleaning keeps it looking right; neglected, it becomes a dulled surface, and algae in a shaded position is genuinely slippery.

Sacrificial ply

Some specifications include a top ply treated as sacrificial: it takes the wear, the scratching and the frit, and if damaged the structural plies beneath are untouched.

Worth asking about on a surface that will see heavy use.

Repairing scratches

Light surface marks on plain glass can sometimes be polished. On a fritted surface that is not possible without removing the frit, which removes the slip resistance.

So prevention is the answer: lift furniture, protect during work above, and keep grit swept.

The surface wears rather than scratching

The top face of a walk on rooflight carries an anti slip treatment, either a ceramic frit fired into the glass during toughening or an etched pattern. Neither is a coating that can be scratched off in the way a film would be, but both are wearing surfaces.

What you see over years is gradual dulling and polishing of the pattern in the traffic route rather than individual scratches, and the effect is a loss of grip before it is a loss of appearance.

What actually causes it

Grit underfoot. By a wide margin the main cause. Sand, soil and gravel dragged across the surface on shoes act as an abrasive under load. A doormat at the door onto the terrace does more for the life of the surface than anything else you can do.

Garden work. Sweeping soil or gravel across the pane repeatedly, or dragging furniture and pots.

Wrong cleaning. Wire brushes, scouring pads and abrasive creams all damage the pattern. Water and a soft brush is the method.

Metal. Furniture feet without protection, tool edges, and anything dropped point first.

Frit against etched

A fired ceramic frit is part of the glass and considerably more durable. It is slightly more visible from below and it will normally outlast the sealed unit beneath it.

An etched or sandblasted texture roughens the surface mechanically and wears more visibly on a heavily used route.

Where the unit sits on a route people cross every day, specify fritted.

Whether it can be repaired

The anti slip treatment cannot be renewed in place. Polishing out a scratch would remove the pattern, which is exactly what you do not want.

Where a surface has worn to the point of being a hazard, the unit is replaced. That is a straightforward swap into the existing structural opening provided the opening and the drainage were built correctly, and it is considerably cheaper than the original installation because the structural work is already done.

The underside

Ordinary glass, cleaned with ordinary glass cleaner and a soft cloth. Scratching happens where somebody uses an abrasive on it, which is easily avoided.

Practical prevention

A doormat. Clearing the perimeter drainage channel so grit and silt do not wash across the pane. Cleaning with water and a soft brush rather than anything harsher. And not leaving heavy items standing on it, which is a loading consideration as much as a surface one.

What to do about a worn surface

Nothing, unless it has reached the point of being a hazard. The anti slip treatment cannot be renewed in place, and polishing out a scratch would remove the pattern, which is exactly what you do not want.

Where it has genuinely worn to the point where the surface is slippery when wet, the unit is replaced. That is a straightforward swap into the existing structural opening provided the opening and the drainage were built correctly, and it is considerably cheaper than the original installation because the structural work is already done.

In the meantime, keep grit off it, clean with water and a soft brush, and be careful in freezing weather, because ice on glass is ice whatever the pattern.

Yes, and grit is the cause

Not feet, and not furniture directly. Grit carried onto the surface on shoes, or blown onto it, is what does the damage. Glass is hard, but quartz sand is harder, and a shoe grinding a grain across the pane cuts it.

That is why the top layer of a walk on unit is sacrificial by design. It is expected to accumulate wear over its life, and it is not the layer that carries the safety function.

What the wear looks like over time

Not individual scratches so much as a gradual haze: thousands of fine marks that scatter light. It reduces clarity and transmission, and on a unit that is the main daylight source for the room below, that matters.

It also shows most in low sun, which is when a terrace tends to be looked at.

What reduces it

Keep it clean. Regular washing is not cosmetic here; it removes the abrasive before it gets ground in. This is the single most effective thing.

A mat or a change of surface at the approach. Grit arrives on shoes, so intercepting it before the glass makes a real difference.

Lift furniture rather than dragging it. Dragging is what causes the deep marks people actually notice.

A fired ceramic frit, which as well as giving slip resistance provides a textured surface where light wear is less visible than on clear glass.

What does not work

Polishing out scratches. Glass polishing on a structural walking surface is not a domestic operation and removing material from a designed thickness is not something to do casually.

Abrasive cleaning pads, which cause exactly the problem you are trying to solve.