Building Regulations answer
Can a roof window be a fire escape?
It can, but only in a narrow case. The height of the room above the ground decides it, and a loft on a normal two-storey house is on the wrong side of that line.
The answer
A roof window counts as an escape window under Approved Document B only for a room within 4.5 metres of the ground. On a two-storey house the loft sits higher than that, so the means of escape has to be a protected stair. The window still brings daylight and air, but it is not the exit.
How high can a room be and still use a roof window to get out?
Within 4.5 metres of the ground. Above that, firefighters' ladders and a person climbing out of a roof slope cannot be relied on, so the guidance asks for a different route.
Approved Document B is the part of the Building Regulations that deals with fire safety. It treats a window as an emergency exit only where a person could reach the ground safely, or where a ladder could reach them. A roof window counts as an escape window for a room within 4.5 metres of the ground.
Where that applies
A single-storey extension with a room in its roof, or a dormer-less bungalow loft, sits low enough that the line may be met. A conversion over a bungalow is the usual case. A room with its floor well above the ground does not meet the line, however large the window.
Why the guidance draws it there
Getting out through a sloping roof is harder than through a wall window. The sill is higher up a slope, the roof is slippery in the wet, and a drop from an eave is a long one. The 4.5 metre figure is the point beyond which the guidance stops relying on the window.
Which escape route does a loft over two full storeys need?
A protected stair. The stair is enclosed with fire-resisting construction and fire doors, and it leads to a safe exit, so the window is no longer the escape route.
Over two full storeys, a loft room sits above the first floor, beyond 4.5 metres from the ground. So the loft gets a protected stair for its escape, and the roof window is not asked to do that job.
What a protected stair involves
The stair from the loft down to the front door is separated from the rest of the house by fire-resisting walls and doors, so that someone in the loft has a safe way down. In practice that can mean fire doors on the rooms that open on to the stair, and a ceiling and walls that resist fire for a set time. These details are matters of the design and Building Control, and they belong to the conversion's builder and designer.
Where our work fits
We fit and replace the roof window. We do not design the conversion or its stair, and the window we fit is chosen for daylight, air and the roof, not as the exit. If you are converting a loft, the stair design comes first, and the roof window goes in after it has been settled.
If the room qualifies, what should the window be like?
Easy to reach, easy to open and large enough to climb through. The opening style matters, and the details come from Approved Document B and Building Control.
Where a roof window does serve as the escape route, the guidance sets requirements on how big the opening must be and how high its lower edge sits above the floor. Those figures are set out in Approved Document B, and the survey checks the chosen model against them.
Opening style
The sash has to open far enough to climb through, and the handle has to be easy to reach in a hurry. A top-hung sash that swings out and stays open can suit, and a centre-pivot can too, depending on the model. How each style swings is set out in the pivot and top-hung comparison.
Not every model qualifies
A window sold for daylight and ventilation may not open wide enough, or its sill may sit too high, to be used as an exit. A model meant for escape is a specific choice from the maker's range. If you want the window to count, say so at the survey, so that we choose the right model from the outset.
Who confirms the escape route is acceptable?
Building Control. A loft conversion is notified to the local authority or a registered building control approver, and they decide whether the escape arrangements meet Approved Document B.
Cutting a new opening in a roof is building work, and it is notified to Building Control: the local authority or a registered building control approver. A whole loft conversion is a bigger piece of building work, and the escape route is one of the things the control body looks at.
Where the window comes in
When we fit a roof window, we handle the notification for the opening itself where the work is notifiable. If the window is part of a conversion that has its own designer and builder, the conversion's escape arrangements are theirs to settle with the control body. The window we fit needs to match what they have specified.
Flats
A roof window in a flat needs planning permission, because flats have no householder permitted development, and the title or lease says who owns the roof. Escape arrangements for a flat's loft are a separate question for Building Control. Fitting itself is covered under roof windows.
Settle these before the window is ordered
- How many storeys the house has below the loft room
- Whether the room sits within 4.5 metres of the ground
- Who designs the stair, and whether it is protected
- Which window model the designer has specified
- Whether Building Control has the plans
Escape-route points for lofts
Can I use a roof window as my only way out of a loft bedroom?
Only if the room is within 4.5 metres of the ground and the window meets Approved Document B. On a two-storey house the loft is higher than that, so the guidance asks for a protected stair instead. Building Control confirms the arrangement on your plans.
Does a bigger window make it count?
No. Height above the ground decides whether a window can serve as an escape at all. A large opening in a room above the line does not meet the guidance, though it helps with light and air. Size matters only once the room qualifies.
Do I need an escape window in a bungalow loft?
A bungalow loft is more likely to sit within the 4.5 metre line, so a suitable roof window can be the escape route. The details come from Approved Document B, and the designer and Building Control confirm them. We choose a model that fits the specification.
Do you design loft conversions?
No. We install and replace roof windows and other rooflights. A conversion has its own designer and builder, who deal with the stair and the escape arrangements. Our part is a window chosen to match their drawings.