The short answer
Usually, yes, within limits. A walk-on rooflight is designed to carry people, and light furniture such as a chair, a small table or a lounger is often fine if its weight is spread across the glass. Heavy items, tightly concentrated loads and large planters are another matter. The deciding figure is the loading the manufacturer states for that specific unit, so get it in writing before anything is placed on the glass.
The glass is rarely the weakest point. Furniture goes wrong through small contact areas, wet weight and what it does to the surface, not through a sudden failure of the pane.
Why point loads matter more than total weight
Walk-on glass is rated for a load spread over an area, and often for a smaller concentrated load as well. A person standing on two feet puts their weight through a patch of sole. A table with four slim metal legs puts the same weight through four tiny points, and each point is pressing on glass with much more force per square centimetre than a boot would.
This is why a heavy item on narrow legs is a worse idea than a heavier one on a broad base. If you must place a table on the glass, rubber or felt pads under every foot make a real difference, and so does a wide, flat foot rather than a spike. The same goes for ladders, step stools and wheeled items, where a hard wheel carries the load on a very small contact patch.
Ask the manufacturer for both numbers: the distributed load and the point load for the unit you are buying. If they only give one, ask for the other. Our answer on how much weight a walk-on rooflight can take explains how those figures are set and what they mean in practice.
Planters and pots: the heavy case
A planter looks light until it is watered. Wet soil is heavy, and a large trough on a terrace can weigh far more than the person who fills it. On top of that, a planter standing in one place keeps its load on one patch of glass for months, and its base holds moisture and grit against the surface.
If planters are part of your terrace plan, there are better places for them than the glass:
- on the solid roof surface beside the rooflight, where the structure below is designed for them;
- on a raised timber or metal frame that stands clear of the glass and bears on the build-up around it;
- in lightweight containers, kept small and moved occasionally, if you want something on the glass for a short time.
Whatever you choose, leave the drainage path clear. Water that cannot run off the glass sits on it, and standing water on a terrace is both a slip risk and a magnet for algae and limescale. The principle behind where things go on a terrace is covered in our guide to walk-on rooflights for roof terraces and balconies.
Scratches, grit and the surface of the glass
Furniture does not have to break glass to damage it. Dragging a metal-framed chair across a pane drags every grain of sand and grit with it, and the scratches cannot be polished out of toughened or laminated glass. They show most in low sun, when light skims the surface.
If the glass has an anti-slip finish, such as a fritted pattern or an etched surface, the pattern protects against slipping but can also hold dirt. Furniture feet can grind that dirt into the finish. Lifting furniture rather than sliding it, sweeping before you set anything down, and using soft pads under every foot will keep the surface in good order. If you are choosing between finishes, our guide to anti-slip glass for walk-on rooflights compares them.
Shade, heat and the room underneath
Anything standing on the glass shades it, and shade is not always welcome. A parasol base, a sofa or a big table over a rooflight will block daylight from the room below, which is usually the reason you fitted it. A dark cushion or mat left in full sun can get hot, and that heat is passed into the glass.
The room underneath is worth thinking about too. Furniture that sits over the glass is also, in effect, sitting over the ceiling opening. Anything dropped or knocked over lands on the pane and may be visible from below, and a ring of damp under a pot shows as a stain on the lining. The finish inside is something you will look at daily, so it is worth keeping the glass above it tidy. A lining that has been splayed and painted crisply deserves a clear pane above it.
A practical rule of thumb
Treat the glass as a floor you walk on, not a table you set up on. For regular, long-term furniture, build the layout so the legs and feet stand on solid surface beside the rooflight, and keep the glass for people and for light. For occasional use, such as a chair for a summer evening, keep to light items with soft feet.
A short checklist before you place anything:
- Check the manufacturer's distributed and point load figures for your unit.
- Add up the item's weight when full, loaded or wet, not when empty.
- Look at the contact area: wide flat feet are better than narrow legs.
- Put pads under every foot, and lift rather than drag.
- Keep drainage clear and the glass swept.
Planning the terrace around the glass
It is easier to decide where furniture goes before the rooflight is fitted than after. At survey we look at the roof, the structure below and how you intend to use the space. If you want a table and chairs in a fixed spot, the rooflight can be positioned beside it. If you want the glass to carry foot traffic across a walkway, we can plan that route and keep the furniture to the edges.
The wider picture of what we fit is on our walk-on rooflights page. Where children use the terrace, see also our answer on whether a walk-on rooflight is safe for children, because furniture can create climbing points as well as loads.
When you are ready, ask for a quote and tell us what you plan to put on the glass. We will record the loading of the unit in your written quote, so you know exactly what it was specified to carry.