The short answer
Yes. A roof window suits a bathroom well, and it is one of the rooms where daylight from above works hardest, because a bathroom often has no outside wall to put a window in. The points that matter are condensation, the finish around the opening, privacy and, over a shower, the specification of the window and its lining. A skylight over a shower is entirely possible when those are planned from the start.
Choosing the window
A bathroom window spends its life in steam, so the frame and the finish matter more than they do in a bedroom. Polyurethane-coated frames, which are white throughout, handle damp air better than painted timber, and they are the usual choice for bathrooms and kitchens. Painted pine can be used, but it needs a good paint film kept intact. If you are looking at VELUX, the white polyurethane versions are the GGU (centre-pivot) and the GPU (top-hung).
Opening matters too. A window you can open lets steam out after a shower and also contributes to ventilation under Part F, which is a good reason to choose an opening window over a fixed rooflight. An electric or solar opening window is worth considering where the ceiling is high or the window is out of reach, which is common over a bath or in a loft bathroom.
Obscure or frosted glass is available for bathrooms where the window is overlooked, which is rarer with roof windows than with wall ones but does happen on a hillside or next to a taller building. Glass in a bathroom does not have to be obscure for privacy from the street, as a roof window looks upwards, but a neighbour's upper window may see in.
Over a shower or a bath
Putting a window directly above the wet area is fine, with a few conditions. The glass should be double glazed with a laminated inner pane, which is good practice for any overhead glazing and gives some reassurance in a room where people are wet and barefoot. The lining and the finish around it need to cope with constant steam, which means moisture-resistant board or a render, and paint made for bathrooms. Where a window sits above a shower tray, condensation on the glass will run down the pane, so the window should have the proper condensation channel at the bottom and a lining that slopes slightly away from the room, not a flat sill where drips settle.
The window should also sit where you can reach it. Reaching up to a pivot window above a shower is awkward, so a control bar, a pole or an electric opener is worth the thought at the survey stage. Blinds are available in moisture-resistant fabrics, and a blind is useful in a bathroom where the sun comes straight in at certain times of day.
Condensation and the lining
Bathrooms make a lot of moisture, and it is the coldest surface that collects it. A window with a well-insulated frame and a warm-edge spacer in the glass runs warmer, so less condensation forms. The lining matters just as much. If the plaster or board around the opening is cold, because the insulation behind it is thin or has gaps, steam condenses there and the paint starts to mark, then blister. For that reason, the insulation around the frame is checked and made continuous before the lining goes on.
The lining itself should be formed so that moisture runs off it and not along it. A splayed lining gives a sloping sill and sends light into the room, which helps to dry it too. The finish is typically a skim with a moisture-resistant paint, or a panel finish, and the edges are sealed against the frame. This is what we record in the finish schedule: the lining shape, the material and the decoration, so it is decided before the roof is opened and not improvised.
Ventilation and the extractor
A window is not a substitute for a bathroom extractor fan. Where there is no outside window, Building Regulations expect mechanical extraction, and a new bathroom or a changed one may fall under Part F. An opening roof window can add purge ventilation on top of the fan, and in a room that already has an extractor fan, a good window helps clear lingering steam. Mention both at the survey so the fan duct and the window are planned together, since the duct may need to pass through the same roof space and avoid the new trimmers.
Planning and Building Regulations
On a house, a new roof window is generally permitted development as long as it stands out from the roof slope by 150mm or less and sits below the ridge line. Flats, listed buildings and some conservation areas follow different rules, so the council planning team can tell you where your home stands. Opening up an existing roof is also building work, because rafters are trimmed and the window has to satisfy Part L, so Building Control must be told. We make that notification when the job requires one.
When a sun tunnel is the better answer
Where the roof is shallow or the space is tight, a sun tunnel may suit the bathroom better than a roof window. It brings daylight through a small, round or square opening, down a reflective tube, to a diffuser in the ceiling. It does not open, so the extractor fan still does the ventilation work, but it fits between joists with little structural alteration. Our page on sun tunnel installation explains where one does the job and where a roof window is the better choice.
What to expect on the day
Bathrooms are small and the sanitaryware is hard to move, so we cover the bath, shower tray and floor before the ceiling is opened, and dust is kept contained. The roof window is fitted from the roof with the flashing lapped into the covering; for the order of work see can roof windows be fitted from inside. Then the lining is formed, boarded or plastered, and left ready for paint or painted. The room is left clean.
If you have a bathroom in mind, a survey lets us check the roof, the ceiling and the position of the pipes and extractor. See roof window installation in Exeter for the full picture, and when you want a written quote, use the quote form.