An electric rooflight for a stairwell: let the house breathe

Warm air rises, and in a house it rises up the stair. A rooflight that opens at the very top gives that air a way out, and the cooler air from the ground floor follows it in.

The physics is plain. Air heated by cooking, electronics, sunshine through the south windows and the people in the house is lighter than the air around it. It drifts up through the open stair and pools under the landing ceiling or the loft hatch. On a warm evening in a 1960s Crawley semi, the top landing can be the warmest spot in the house, and it is also the route to the bedrooms. With the rooflight shut, that heat sits against the ceiling and works its way into the rooms beside it.

Open the rooflight and the pool drains. The stair begins to act as a flue, pulling fresh air through any window you have opened at the bottom. It is a slow, steady movement, not a gale. We write about the general principle on our page about how an opening rooflight can help cool a house in summer. The stairwell is simply the best place to put that principle to work, because the vertical run is already built for you.

Light is the second gain. Many terraced and semi-detached stairs are lit by a single small window on the half landing, or by nothing at all. A rooflight at the top sends daylight straight down the well, so each flight gets some of it. A fixed unit would do that job. The opening version does it and gives you the ventilation as well.

A manual opening rooflight over a stairwell is often too high to touch. The ceiling above a landing can sit five or six metres above the floor of the hall, and the stair itself is in the way.

Think about how you would open a manual unit. You stand under it, reach up to a handle or a pole hook, and push. Over a landing, there may be a stair flight and a balustrade between you and the spot directly below the glass. You would be leaning out over the void with a pole. That is an awkward thing to do once, and nobody would do it every evening.

A motor removes the problem. The switch goes on the wall at a comfortable height, at the top or bottom of the stair, wherever you pass. You press it, the sash lifts, and you carry on up to bed. The same switch closes it again. The general case for paying for the motor is covered on our page about whether an electric rooflight is worth it over a manual one, and for a stairwell the answer leans firmly towards electric.

There is also a care point. A rooflight high above a stair is hard to clean from inside. A motor opens the sash wide enough for the inner face to be wiped from a safe position, which we describe in looking after an electric rooflight.

Stairwells sit under three very different roofs, and each one changes the product and the upstand. Identify yours first.

The first is a pitched roof with a loft above the stair. The landing ceiling is often boxed in below the rafters, and there is a void between the ceiling and the tiles. Here the rooflight is a roof window, and the job includes a light well: a shaft lined with plasterboard that carries the light from the roof down to the landing ceiling. The shaft is usually splayed, wider at the bottom than the top, so the light spreads rather than falling as a narrow beam.

The second is a flat roof over a rear or side extension, with a stair rising beside it. Many 1950s and 1960s Crawley houses have a flat-roofed section at the back, and some have been extended upwards over a staircase. The rooflight there is a flat rooflight on an upstand, and the kerb gives you a dry position for the motor and a good sash height.

The third is a converted loft, where the stair continues up to a new bedroom. The landing for the loft stair often has a sloping ceiling and a lot of wall. A roof window at that level, aimed at the stair, can light two floors at once.

Our pages on roof window installation and flat roof rooflight installation describe the two families in full. The choice between them is made by the roof, not by taste.

A stairwell is an escape route and a fall risk, so the rooflight above it is checked against the regulations that cover both. We assess this at survey, before any product is ordered.

Approved Document B treats the stair as a route out of the house in a fire. In an ordinary two-storey house that seldom restricts a rooflight. Where a loft conversion adds a third storey, the stair becomes a protected route with fire-resisting doors and walls, and the light shaft has to respect those enclosures. A shaft that passes through a fire-resisting ceiling has to keep the rating. We check the layout against the drawings before the design is fixed, and where the work is notifiable we handle the Building Control notification.

Approved Document K covers protection from falling and from impact. Glass above a stair can drop onto people below if it breaks, so the inner pane should be laminated, which holds together when damaged. That is the normal specification for any rooflight we fit over a place where people walk. It also happens to be the same pane that makes a room quieter, so the choice serves two purposes.

Part F covers ventilation. The stairwell rooflight can contribute to purge ventilation, the rapid clearing of a room on demand, but it does not replace the background trickle ventilation the rest of the house requires. Think of it as an extra that you control, rather than a substitute for the vents in the window frames.

A stairwell is a narrow space, so the rooflight is usually small. Size it to the well, to the ceiling above, and to the airflow you want, in that order.

Measure the plan of the well first. A typical stair void in a 1930s or 1960s house is between 800 and 1,000 millimetres wide and two to three metres long. A rooflight that matches that footprint lights the whole flight and leaves a clean line of plasterboard around it. A unit much larger than the void would land on the wall or the landing ceiling at one end and look awkward below.

Then look at the ceiling above. On a pitched roof, rafters run in a fixed rhythm, often at 400 or 600 millimetre centres. A roof window that fits between two rafters needs only a simple frame. One that cuts a rafter needs a trimmer and a header, which adds structural work. We measure this from inside the loft before we propose a size. Our page on the roof window service covers the framing in more detail.

Finally, think about the air. The opening needs to be large enough to draw a steady flow without being a hole that lets in rain and drumming when the sash is ajar. A sash lifted a few centimetres is usually enough for a stairwell draw. Fully open is for clearing a hot house quickly. A motor with adjustable stops gives you both, from one switch.

When the stairwell and landing together are deeper than a single unit can cover, two smaller rooflights in a line often look better than one long one. Each keeps a manageable sash and its own motor.

How the sash moves affects how well it ventilates, how it looks from the landing, and how it behaves when the weather changes.

A hinged sash lifts at one edge, like a window. It gives a good opening with a short motor stroke and suits the smaller units common over stairs. A sliding sash runs on rails and gives a wide clear opening, but it needs a larger unit and a flat roof. Sliding units are more at home over a roof terrace than a narrow stair. Our page on choosing between hinged and sliding walks through the trade-offs, and for most stairwells hinged is the natural answer.

Think about where the sash lands when it is open. Over a stair it can be a problem if the raised edge sits above the landing with no rain cover. On a pitched roof the sash opens outwards and upwards, with the upper edge leaning clear of the roof plane. On a flat roof the sash tilts on its upstand, and the gap at the open edge is the point where wind can push rain. That leads to the next topic.

An open rooflight over a stairwell lets rain reach the stair carpet if nothing closes it. That is why the sensor matters more here than in almost any other room.

Stairs are not a place where you notice a wet patch quickly. You are not sitting under the skylight at dinner. You are in another room, or out of the house. A rain sensor closes the sash on the first drops, without anyone touching a switch. We describe the sensor, where it sits and how it is set in our page on rain sensors on electric rooflights, and the related answer on whether electric rooflights close by themselves when it rains gives the short reply.

Wind is the other trigger. A sash that opens on a windy afternoon can be pushed against its stops. Some actuators include a wind or load limit that stops the motor if it meets resistance. We set the opening angle for the roof and the exposure of the site, which, in the Weald, can be quite different from a sheltered town garden.

The rule is to treat the stair as a dry zone that you protect with the sensor, not with luck. A stairwell unit that opens only while you are at home and watching is a half solution.

A stairwell carries sound as well as air. It works in both directions: noise from outside falls down the well, and noise from the house rises up it.

That matters because a rooflight is the thinnest part of the shell. Rain on a flat rooflight drums. Aircraft on the Gatwick routes are heard through thin glass. Road and rail noise from the M23 and the Brighton main line finds the same weak spot. Over a stairwell, a hard-walled shaft, a polished hall floor and a high ceiling can make the sound carry further, because there is little soft furnishing to soak it up.

The answer is in the build of the unit. A laminated acoustic inner pane, chosen for the thickness and interlayer that suit the room, dulls the impact of rain and lowers the airborne noise. Good seals stop whistles around the sash, and the upstand finish keeps the frame from ringing. Our quiet spec describes how we write this down for every quote. You can read the detail for electric units on whether an electric rooflight can have acoustic laminated glass, and our answer on whether opening rooflights let in more noise than fixed ones is honest about the difference.

The motor itself is not a noise concern on a landing. It makes a low mechanical hum for the short time the sash moves, and nothing when still. The page on whether electric rooflights are noisy when they open and close explains what you will hear.

An electric rooflight needs a mains feed or a low-voltage supply, a control cable, and somewhere sensible for the switch. A stairwell makes all three easy or awkward depending on the house.

Over a stair, the route for the cable is often down the light shaft or along the loft floor to the nearest lighting circuit or a new spur. The feed to a flat roof kerb can come through the ceiling void below. We plan the run at survey so that the cable sits inside the finished plaster, not in trunking down the wall. The full picture is in our page on wiring and powering an electric rooflight. The question of who does the electrical part has its own short answer under does an electric rooflight need an electrician.

The switch position is a design choice. On a stair there are three obvious places:

• Beside the existing landing light switch, where everyone already reaches.
• At the foot of the stair, so the last person to go up can open it.
• On a remote handset or a wall keypad that can live in a bedroom.

Remote and keypad options are covered in controls for electric rooflights. The smarter end, including voice assistants, appears under electric skylights with Alexa or Google Home.

Think about the power cut as well. The stair is a place where you want the sash to fail into a safe state. Most actuators can be closed with a manual override, and the page on what happens to an electric rooflight in a power cut describes how it works.

A rooflight over a stair should be safe for a child on the landing, and safe for a child who is not near it at all. Both matter.

The glass over the well is laminated, which means a child cannot fall through, and nothing drops if it cracks. The sash is out of reach, because it sits at ceiling height above the void. A motor that opens only when a switch is pressed, with the switch at adult height, gives far better control than a pole or a cord. Some controls allow a lock-out so that a handset cannot operate the sash by accident. Our page on whether an opening rooflight is safe with young children covers limiters, locks and sensible positions.

The guard at the stairwell is a separate matter. The balustrade, the newel and the landing rail are there under Approved Document K, and a new rooflight does not change them. It does change what you see when you look up, and a lighter stairwell helps everyone judge the steps.

The cold surface at the top of a stairwell is where moisture gathers. A well-made light shaft keeps it off the plasterboard.

Warm air rises up the stair and meets the coldest surface in the house: the glass. If the shaft walls are uninsulated, the plaster above the landing can sweat and, over a winter or two, grow mould. We line the shaft with insulation and seal the gap between the frame and the plaster with a vapour-control detail, so that the warm air cannot reach the cold side. The glass itself is a double or triple sealed unit with a warm edge spacer, which holds the inner face warmer than a basic unit would. Our hub on energy efficient rooflights explains the thermal side in detail.

Opening the sash in winter is a small decision too. A short burst of ventilation clears damp air from the stairwell, but it also lets out warmth, so the motor is best used for a few minutes at a time. The controls can include a timer to shut the sash after a set period.

A visit to a stairwell tells us more than any drawing. We look at four things.

1. The void: its width, length and height, and what the ceiling is made of.
2. The roof above: pitched or flat, the rafter or joist direction, and the loft insulation.
3. The route for power, and where the switch would fall naturally.
4. The sound on the landing: aircraft, traffic, rain on the existing roof, or the house itself.

From that we write a proposal with the unit, the shaft, the glazing build, the control and the price, and a quiet spec for the room. The work is installed to current Building Regulations and made good inside, with the plaster and paint finished, and it carries our 10-year workmanship guarantee. When you are ready, you can get a quote or message us on WhatsApp. Our electric and opening rooflight hub lists every page in this series.

These are the points that come up once the idea of a stairwell rooflight has settled in.

Can an existing fixed skylight over my stairs be made to open?

Sometimes. The frame, the glass weight and the upstand decide. A fixed unit is often replaced with an opening one of the same size, and the motor goes in at the same visit. Our page on swapping a fixed rooflight for one that opens sets out how that works.

Will the rooflight make the landing too bright at night?

It lets in whatever light is outside, so a clear night with a moon or a bright street can show. A blind fitted under the glass controls it. See fitting a blind to an electric rooflight for the options.

Do I need an insect screen over a stairwell?

If you plan to leave the sash open in the evening, yes, it is a sensible addition. Wasps and moths are attracted to the landing light. The screen sits in the frame and lets air through. The question is covered under insect screens on electric rooflights.

What does it cost?

The price depends on the roof, the size, the glazing build, the light shaft and the electrics. General market ranges are on our costs page, and the factors behind them are in what affects the cost of an electric rooflight.