Can a roof window be a fire escape?

Fire guidance for houses starts from a simple idea. If a fire blocks the stair, someone in a room upstairs needs a second way out, or a stair that the fire cannot reach. The Building Regulations deal with this in Approved Document B, and the answer depends on how high the room is above the ground and what lies below it.

A loft room is the awkward case, because it is the highest room in the house and often the furthest from the front door. Whether a window counts as an exit turns on whether a person can get to the ground from it, or be helped from outside. The guidance sets its tests in numbers, and the right place to read them is the document, with the people who sign off the work confirming how they apply to your room. Our wider guide to roof windows and the Building Regulations sets escape alongside heat loss and structure.

The guidance uses a height of 4.5 metres to separate two kinds of room. Rooms below it can use a suitable window for escape. Rooms above it are handled differently, and the usual answer is a protected stair. That is a staircase walled in with fire-resisting construction and fitted with fire doors, so that it keeps working as a route down to the ground floor and the front door.

Put a loft over two full storeys and its floor will usually sit higher than that mark. A new loft bedroom there therefore usually needs a protected stair, whatever size of roof window is fitted. That is a bigger change than most owners expect, since it can take space from the landing and the rooms below. It is better to hear this at the planning stage than after the structure has been opened up. Our answer on roof windows for loft conversions works through typical layouts.

The position is lighter on a bungalow, where the loft room is a first floor with a ground floor below. Here a roof window can be accepted as the escape window, so a chalet bungalow with bedrooms in the roof often depends on one. Bognor, Felpham, Pagham and the Peninsula have many of these homes, with hipped roofs and dormers added over the years.

The guidance fixes the size of the clear opening, how high the sill stands from the floor and the way the window opens. Approved Document B asks for a clear opening of at least 0.33 m², 450 mm high and wide, with its bottom no more than 1100 mm above the floor. A window sold with an escape option has to be checked against the actual room. Where the sill is too high to climb through, or the pitch makes the opening awkward, a different unit or a different position may be needed. We note the floor-to-sill height on the survey, and a measured drawing of the slope helps the inspector decide quickly.

A window that is fixed shut cannot be an escape, so a fixed unit chosen for the view or the price needs another way out. Obscure glazing in a side slope is a planning matter and does not remove the need for escape. The same goes for a window that opens only a crack for ventilation.

Position matters as much as size. A window placed behind a built-in wardrobe or furniture is no use, and a window that opens onto a roof pitch with a long drop below calls for particular care. An inspector asks about each of these points, and the answers belong in the drawings, not in a note added after the work. Keep the drawings you send to building control, because they are the record of what was approved. If the room is later sold as a bedroom, the buyer's surveyor will look for exactly that paperwork, and a loft room without it can be described as a store room instead.

Start with the number of storeys under the loft and the room you plan to use, then speak to your building control body, either the council's own team or a registered building control approver. They can confirm whether a window is acceptable or whether the stair must be protected. In the South Downs National Park, building control stays with the district council. Ask which route suits a small job like this, and ask when the inspector wants to see the opening, since some checks happen before the lining goes on.

We photograph the roof and the loft at the survey, and once the layout is settled the written quote comes as one price. If the answer is a protected stair, we will say so before any window is ordered. The glazing must also reach the limits in Approved Document L, as our answer on the U-value for a new roof window explains. More about the work is on our skylights and roof windows page.