Choosing a roof window starts with a simple question that people often skip: how should it open? The answer shapes how much headroom you have when it is open, how easily you can clean the outside, what the view is like, whether it can serve as an escape and how it looks on the roof. Makers offer a large menu, but most windows fall into a few types. This guide describes each one, says where it works and where it does not, and ends with a way to choose. It covers the roofing side. The rules on planning and Building Regulations have guides of their own, linked as we go.
Centre-pivot windows
The centre-pivot is the classic roof window. The sash turns about a horizontal axis near the middle of the frame, so the top half swings outward and the bottom half swings in. A handle at the top or bottom lets you open it, and most designs lock in several positions, including a ventilation position with a small gap. You can turn the sash right round for cleaning the outside from indoors, which is a big advantage on a roof you cannot reach safely.
The pivot design suits roofs of moderate pitch. Because the lower half swings inward, you need clear space under the window, which can mean keeping furniture away or fitting it higher up the slope. The handle at the top can be awkward to reach in a high window, so a bar or pole is supplied, or the handle can be placed at the bottom on some models. Centre-pivot windows are common, widely stocked and usually the least expensive choice, and one trade guide has a standard centre-pivot at anywhere from £680 to £1,300 fitted.
Top-hung windows
A top-hung window is hinged at the top and opens outward at the bottom, like a awning. Some pivot higher up the sash so that you can lift it and see out at a good height. In the low-pitched roofs of a loft conversion the top-hung is a better answer, because it opens a large gap at eye level and lets you lean out. Many models have a second position in which the sash locks at an angle for ventilation with rain kept off. There is no inward swing, so furniture can stand directly beneath.
The trade-offs are that a top-hung window cannot usually be reversed for cleaning from inside, though some can be tilted in, and the sash projects outward when open, so wind catches it. It also costs more than a centre-pivot of the same size. Some top-hung versions are designed as escape windows with a wide opening, relevant to loft bedrooms, as in what is an escape roof window. Our guide to roof windows for loft conversions deals with the rules on escape and size.
Fixed windows and combination windows
A fixed window does not open at all. It is cheaper and has fewer parts to wear, and it can be set very close to the covering. Fixed windows suit stairwells, landings, hallways and rooms with other means of ventilation. They are also used above a venting window, or as extra panes in a bank, to bring more light. A fixed window can be a good choice in a bathroom with an extractor fan, where the glass is for light only.
Combination windows pair two units in one frame, usually a fixed or opening unit over another, to give a taller window from eaves to roof. They are sold as a set with a joint flashing kit, which closes the join between the pieces. Because the joint is a weak point in a roof, combination windows should always use the maker's combined kit and not two separate ones. See roof window flashing kits for why.
Balcony and cabrio windows
Some makers sell windows that open into a small balcony or a roof terrace. The top sash swings up, and the bottom half folds out to form a railing and a floor. They are impressive but costly, structurally demanding and heavier than standard windows, and they need a roof pitch and a rafter layout that work with them. The Building Regulations, planning rules and structure all need care. If you are interested, bring it up at the survey, because the opening size and the position of the rafters decide whether it is possible.
Conservation rooflights
For period and listed homes the conservation rooflight is a different design philosophy. It has a slim metal frame, a flush profile, a central glazing bar and a dark finish. It is generally fixed or hinged at the top, and does not pivot. It is made to look like a traditional cast-iron skylight with modern double glazing. Our guide to conservation rooflights for period and listed homes deals with it in full, including the consents that apply.
Flat roof rooflights and lanterns
A roof window is made for a pitched roof. On a flat or very low-pitched roof the equivalent is a rooflight on a kerb, or a lantern. They work differently, with an upstand that stands proud of the roof and a membrane that is turned up to meet it. Our page on flat roof rooflights compares fixed, opening and walk-on types, and the answer on roof lantern or flat rooflight compares shapes.
Sun tunnels
Where there is no room for a full window, such as above a landing, a hall or a dark bathroom, a sun tunnel brings daylight down through a reflective tube. It is a different product and has its own page: sun tunnels.
Frames and finishes
Most standard roof windows come in one of three frame materials. Pine, either clear-lacquered or painted white, gives a warm look inside and suits bedrooms and living spaces, though it needs care in damp rooms. White polyurethane-coated timber resists moisture, and is the common choice for kitchens and bathrooms. Aluminium or other metal frames are slim and strong, and used for large windows and conservation styles. The outer cladding is usually aluminium in grey, black or other tones, chosen to match the roof covering. Glass options include standard double glazing, noise-reducing glass, solar control glass and laminated or toughened panes where safety requires it.
Electric and solar-powered models open and close at the touch of a button, with rain sensors that close the window automatically on better models. They help with high windows that are hard to reach. Our answer on are electric roof windows worth it gives the pros and cons.
Where each type works best
Loft bedroom with a low eaves wall: top-hung windows, or a pair of centre-pivots set high, give headroom and a view without a window at floor level. Where escape is an issue, the opening size and sill height drive the choice.
Dormer-less loft study or playroom: a centre-pivot at a comfortable height is practical, and the reversal for cleaning is a boon when the roof cannot be reached.
Landing, stair or hall: a fixed window or a sun tunnel. Nobody needs to open it, and every moving part you leave out is one less to wear.
Bathroom: a moisture-resistant polyurethane-finished window with a ventilation position, working alongside an extractor fan, not as a replacement for one.
Kitchen extension: usually a flat-roof rooflight or lantern and not a pitched roof window.
Period house in a conservation area: a conservation rooflight on the rear slope, after speaking to the planning team or conservation officer.
Roof with a view: the balcony or cabrio types are possible, though they ask for a particular pitch and rafter layout, and they change the roof structure.
None of this is a rule. It is where the usual balance of cost, use and appearance falls, and your roof may point somewhere else. A south-facing slope that gets very hot, for instance, may call for solar control glass and an external blind whatever the type. Our answer on whether roof windows make rooms hot covers that.
Roof pitch and covering limits
Not every window suits every roof. Each model has a range of pitches it is designed for, and a window used outside that range will leak or fail to operate properly. Pitch also affects how much headroom a top-hung or pivot window gives. The thickness and profile of the covering matter, because the flashing kit must be matched to it, as set out in our guide to the minimum pitch for a roof window. We check both at the survey, and we would rather propose a different type than fit a window that will not work on your roof.
Safety features worth asking about
Look beyond the opening style to what protects the people using the window. Child-resistant catches, restrictors that limit the opening to a safe gap, and tilt-and-lock positions keep a window from opening wide in a child's room. Laminated inner glass holds together if it is hit, which matters above stairs. A sash that can be locked in a ventilation position with a security latch means you can leave it ajar without leaving the roof open to the weather. Better models close themselves when rain is detected. These extras cost little at the time of ordering and a good deal more to add later, so decide on them when you choose the type.
How to choose
Work through five questions. What does the room need: light only, or air and a view as well? Is the roof pitch low or steep, and where will the window sit in the slope? Do you need it to serve as an escape? How will you clean it, given that the outside of a roof window is hard to reach? And do you need to respect the look of the house, perhaps because of a conservation area or a period roof? The answers usually point to one or two types. Bedrooms and living rooms usually want a pivot or top-hung window at a sensible height. Landings and stairs want fixed units. Kitchens and bathrooms want moisture-resistant finishes and an opening position for ventilation. Period roofs want the slim conservation style.
On cost, the type you pick is one of several drivers, and it is the survey that settles your price, so your fixed quote follows the survey. Our guide to how much a roof window costs to fit covers the drivers. For help choosing for your own roof, our roof windows page lists the service and 01256 213956 books a visit where we look at the pitch, the covering and the rafters.
