Why an ordinary rooflight will not carry you
Every rooflight is designed for a particular job, and the job decides the build. An ordinary one has to resist wind, rain, snow and the odd branch or ball. It does not have to take the weight of a person standing on one spot, so it is not made to.
The materials show it. A plastic dome is a thin moulded cap, and it ages: sunshine makes it brittle and chalky, so a dome that looks firm can crack at a step. A glass skylight in a roof window or a flat-roof frame is set at an angle or sits proud of the roof on a kerb, and its glass is chosen for insulation and light, not for standing on. Even a rooflight that has survived a heavy snowfall has not been tested for a foot or a knee.
Looks are no guide. An old dome, a modern flat glass unit and a lantern can all look solid from a distance. Treat every rooflight you did not install yourself as something that will not take weight. People have gone through rooflights they could see perfectly well, and it is one of the worst ways to come off a roof.
The same goes for the rooflight over your own head. A skylight in a loft room, a roof window above a stair, a sun tunnel's dome on the flat roof: each is glazing in a roof, and none is a floor. A ladder leant against the glass, a child's ball on the roof, a ladder foot set on a dome to reach a gutter, all put a point load on a pane that was only ever asked to take weather. A pane that has already misted or yellowed has also lost some of its strength to age, so an old unit is the last one to trust.
This is why anyone who works on roofs checks where the rooflights are before stepping out. It takes a minute, and it is the habit that keeps people out of the room below.
What makes a walk-on rooflight different
A walk-on rooflight is a structural glass unit. It is built to carry people and furniture, in the way a floor does, and it comes with a stated load it has been made and tested for.
- The glass. Several layers, bonded together, toughened or laminated, much thicker than window glass. If a layer breaks, the others hold.
- The frame. Heavier and made to spread the load into a supporting structure, not to hang in an opening.
- The support. The structure round and under the unit is designed for the weight, since the weight has to reach a beam or wall that can take it.
- The surface. The top face is finished for grip, because wet glass is slippery.
If a rooflight is meant to be stood on, someone chose, built and fitted it for that on purpose. Its maker and its rated load should be on paper. If neither can be shown, assume it is not a walk-on unit. The layers and the load ratings are unpicked in the glass and loads guide, and the wider picture is on the walk-on rooflights page.
Working safely near an ordinary rooflight
People do need to be on roofs with rooflights in them: to clear a gutter, check a chimney, or fit a satellite dish. A few habits keep the glass out of the equation.
- Stay off the rooflight, and never put a ladder, tool or knee on it. Even if it looks strong enough.
- Keep a clear route round it. Treat a rooflight as a hole in the roof with a thin lid on.
- Watch out for rooflights hidden by moss, leaves or snow. A flat roof with a dome in the middle can be hard to see in the wrong light.
- Use a board or platform designed for roof work that spreads your weight over a firm part of the structure, and secure yourself to a point that will hold.
- Ask a roofer or the person who installed it, not a guess, before putting any weight near the unit.
If you are not sure how to reach a job safely, the safe answer is to leave it to someone who is.
If you want a rooflight you can walk on
There are good reasons to want one: a roof terrace over a dark room, a patio slab above a basement, a path over a lightwell, or a flat roof you need to step across to reach a hatch. In each case the answer is a unit made for it, not an ordinary one with a hopeful board over the top.
A walk-on rooflight is a structural job. The opening is trimmed through the roof or floor, the support is worked out for the load, and the unit is weathered in so that it stays dry. We survey the position, agree the use with you, and give a fixed written quote after the free survey. If Building Control must be told, we tell them, and the workmanship has our ten-year guarantee.
Two follow-on points have their own pages. How much grip the surface gives is on the slipperiness page, and whether a unit can sit among paving is on the patio and path page.
If your plan involves any foot traffic over a rooflight, ask for the survey before anything else is built, or send us a photo and a rough idea of the use on WhatsApp.