Sun tunnels for bathrooms, landings and hallways

An internal bathroom, or an en suite carved out of the middle of a plan, is one of the best uses for a sun tunnel. It is a room where you want daylight for the mirror and a sense of being awake in the morning, and where a window is often impossible. The tunnel provides a bright, even light from above, and the frosted diffuser means nobody can see in, which removes the privacy question altogether.

What the room asks in return is moisture control. A bathroom puts warm, wet air into the space around the ceiling, and a sun tunnel opens a route from that space to the cold roof. If the diffuser and its collar are not airtight, steam rises into the tube, meets the cold wall and condenses. The first sign is a mist on the inside of the diffuser or a drip on a hot-shower morning. The cure is done at fitting, and we describe it in do sun tunnels cause condensation. A sealed ceiling collar, an insulated tube through the loft and loft insulation tight to the tube between them keep the wall warm enough that the moisture stays in the room, where an extractor can deal with it.

That last point is worth stating plainly. A sun tunnel lights a bathroom; it is not ventilation. A bathroom without a window still needs mechanical extract to meet the ventilation requirements in Approved Document F, and in a room that already has a working fan, the tunnel simply adds light. A tunnel should never be treated as a way to vent steam to the roof, and the tube is sealed from the room so that it does not become one.

The finish matters more here than in any other room. Paint in a bathroom ceiling should be a moisture-resistant or bathroom emulsion, and the join between the plaster and the diffuser trim wants a thin, flexible bead of sealant so a hairline crack cannot open as the materials move at different rates. On a new plasterboard ceiling that is straightforward. On an older plastered ceiling, we match the plaster to what is there and make good around the opening so there is no ridge.

Position inside the bathroom is a small decision with a visible result. Over the basin and mirror, a tunnel gives the face the best light for shaving or make-up. Over the bath, it lights the tub and tiles but leaves the mirror in shade. In a very small room, the centre of the ceiling is usually the safe answer, because it keeps the disc clear of the extractor, the shower enclosure and any boxed-in pipework, and gives the light a chance to reach every wall. We mark the choices on the ceiling at survey so you can stand under them and decide.

Many houses have a landing that gets no daylight. It is the same story in the 1930s semis of Heavitree and Pinhoe, the Victorian terraces of St Thomas and Newtown, and plenty of larger Georgian houses in the city: the rooms have windows, the staircase and landing run through the middle of the house, and they do not. A sun tunnel above the landing lights the top of the stairs, the doors off it and, depending on the plan, part of the staircase beneath.

The landing is a place where position matters. Put the diffuser above the point where the light is most missed, which is usually the head of the stairs, since that is where people hesitate on the way up. If the landing is long, one tunnel at one end leaves the other end dim, and two smaller ones can serve better than a single large one. A diffuser close to a door will light the room beyond when the door is open, which a diffuser in the middle of the ceiling may not.

The roof route is the other question. The tube has to go from the landing ceiling through the loft to the roof, and on many houses the landing sits directly under a ridge or hip where roof timbers meet, so the straight line is blocked. A small adjustment of the position, a stepped section of tube or a short flexible one can solve it, and we describe those trade-offs in our guide to rigid or flexible sun tunnels. Where the stair well is tall, the drop is longer than on a normal ceiling, and the light that reaches the bottom will be thinner. That is worth knowing before you choose a diameter.

A long, narrow hallway is a different problem from a landing. It may be the full depth of the house, with a front door at one end and a kitchen door at the other, and a single dark stretch between. A sun tunnel can light the middle. Bungalows, where the roof sits close above the ceiling and the corridor is straight, are the easiest case of all, and the tube can be short, rigid and nearly as efficient as it gets.

In a long corridor, spacing matters more than size. One tunnel puts a bright disc on the ceiling and a pool of light on the floor beneath it, and the ends of the corridor remain dimmer. Two or three smaller tunnels at even spacing spread light more evenly and avoid the effect of a single spotlight. The cost is more openings in the roof, more flashings and more ceiling finishing, so the trade is a real one. At survey we mark the positions on the ceiling and look at the roof above each one before suggesting a number.

A hallway with a high ceiling, as you find in a Georgian terrace or a Victorian villa in Torbay, has a longer tube and so a weaker light at the bottom. Often a larger diameter on a shorter route will beat a smaller one, and sometimes a roof window or small rooflight is the better answer. The comparison is set out in sun tunnel or rooflight: which brings more light.

A bigger tube carries more light, but it needs a bigger hole in the ceiling and a bigger clear route through the roof. For a cloakroom or a short landing, a small diameter is enough. A bathroom, or a hallway that needs real light, benefits from a larger one. The ceiling height matters too, because the light thins with every metre of tube. A low ceiling under a shallow roof is an easy case. A tall landing in a Georgian house is a hard one, and the diameter has to make up what the length takes away.

It helps to think of the room before the product. A small bathroom is lit well by a single tunnel over the centre. A larger family bathroom may want one over the basin and another over the bath. A square landing wants one, and a corridor wants two or three. The question to ask is what you do in that space, and where you stand when you do it.

The amount of light also changes with the day. Sun tunnels work in cloud, but they give less in a dull Devon November than on a bright June morning, and a room that is lit well by day will still need artificial lighting after dark. Some makers offer a light kit that fits an electric lamp inside the tube, which suits a bathroom or a landing, and we cover the details in can a sun tunnel have a light fitted. Electrical work in a bathroom is subject to its own rules, so a light kit in a bathroom is something to agree with the electrician from the start.

Sun tunnels on a house are usually treated like other rooflights for planning, so the permitted development limits for roof windows are the relevant ones: the dome should stand no more than 150mm off the roof plane and stay below the roof's highest point. Conservation areas, listed buildings, flats and national park land can change that, and Article 4 directions can remove rights that normally apply. Listed buildings need consent for external changes, and the planning rules for flats and maisonettes differ from houses. Where any of these applies, ask the local planning authority, and we will say so at survey if your address looks like one of them.

Building Regulations are involved wherever a roof is opened, and the question is which parts apply. A tunnel that fits between existing rafters is a smaller job than one that needs timbers trimmed, and where timbers are cut it is a structural alteration. Any Building Control notification the work needs is ours to make, and we tell you at the quote stage which side of the line your roof falls on.

The roof side is covered in more depth in sun tunnels on flat and pitched roofs, including the different flashings for slate, plain tile, interlocking tile and flat roofs.

Whatever the room, the part of a sun tunnel you live with is a disc in the ceiling. The detail that makes it look finished is small and specific. The hole is cut as a clean circle. The collar sits flat and square behind it. The plaster around the opening is made good so there is no cracked edge or soft corner. The trim ring covers the join, and the paint line against the ring is cut straight.

On a plasterboard ceiling, as in most houses built since the 1950s, the cut is simple and the edge is filled and sanded before the trim goes on. On an older lath and plaster ceiling, the work needs more care: the area around the cut is supported, the plaster is scored rather than broken, and any loose section is secured back. Lime plaster ceilings are made good in lime. The corners of a landing or bathroom ceiling take the most wear and show the most, so that is where the finishing time goes.

Because the disc is a bright spot on the ceiling, any flaw next to it shows up. A shadow line, a patch of uneven paint or a wandering edge draws the eye. That is why the finish schedule sent with each Brightview quote covers the ceiling end of the sun tunnel: the ceiling and roof construction above the room, how the opening will be cut and made good, the trim, whether it is handed over prepared for your own paint or painted, and how dust is managed. You can see it on the finish schedule page.

The quickest way to judge a room is to stand in it with the light off, look up and ask what is above the ceiling. A loft, a flat roof, a stair well and a blocked ridge each point to a different answer. For a fuller picture of how we plan and fit them, read about sun tunnel installation across Exeter and 30 miles around, or ask for a survey. We will look at the roof space, mark the ceiling positions, agree the diameter and tube, and write the finish into the quote before anything is cut.