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Fire Escapes UK

Everything you need to know about fire escape windows

When replacing any window, the escape aperture should not be reduced. If the original window was larger than necessary for the purpose of escape, then the new window opening can be reduced down to the minimum as specified in the criteria below. It is generally good practice to replace any window on the first floor that is not used as an escape window with an escape window.

Why do i need fire escape windows? 

To meet current Building Regulations for new build, all habitable rooms should have a means of escape:

- Ground floor rooms need a fire escape window/door or direct access to a hallway leading directly to a fire escape window/door.
- First floor rooms, not more than 4.5m above ground level, need a fire escape window.
- Second floor rooms and first floor rooms, more than 4.5m above ground level, need a fire-protected stairwell. Please refer to the current version of Approved Document B for more information.

Minimum requirements for a fire escape:

Fire escape windows must provide an unobstructed opening of at least 0.33m².

Minimum opening width: 450mm
Minimum opening height: 450mm

The lowest part of the window must be between 800-1100mm from the floor. 
A step under the window can be installed to meet this requirement.



Opening width: 500mm
Opening height: 700mm

0,5m x 0,7m = 0,35m²

How does a flying mullion work?
A mullion is the middle section of a frame that divides two casements and is usually tenoned into the frame.

We can install flying mullions in all sidehung windows with at least two casements, by fixing the mullion to one of the casements and locking it into the frame with two small flush bolts.

This allows you to open both casements, moving the mullion as you open the master casement and creating a clear opening for means of escape.


For further info please refer to Document B of the latest "Building Regulations