What is the maximum travel distance in a building?

Maximum travel distance depends on the building type and whether escape is available in one or two directions. For dwellings: 9m in any direction. For flats (within the flat): 9m one direction, 18m two directions. For offices: 18m one direction, 45m two directions. For assembly buildings: 15m and 32m. These are measured from the furthest point in a room along the escape route to the nearest storey exit or final exit. AD B Table 2 and Table 3 provide the full details.

What is an inner room and why is it a fire safety concern?

An inner room is a room from which escape is only possible by passing through another room (the access room). This is a fire safety concern because if a fire starts in the access room, the inner room becomes trapped. AD B Section 2 restricts inner rooms: they must not be bedrooms, the access room must not be a high fire risk, the inner room should have a vision panel or be within direct sight/sound of the access room, and an automatic fire detection system should be provided in the access room.

When is a protected stairway required?

A protected stairway (fire-resisting enclosure around the stair) is required in most multi-storey buildings. For two-storey houses, it may not be required if alternative escape from first floor is available. For all buildings of three or more storeys, a protected stair is needed. The enclosure must achieve 30 minutes fire resistance (60 minutes for buildings over 18m), with FD30S self-closing fire doors at all openings. The stair must discharge at ground level to a final exit.

How wide must an escape corridor be?

Minimum corridor width depends on the number of people using it as an escape route. For up to 60 persons: 900mm. For 60-110 persons: 1050mm. For 110-220 persons: 1200mm. For over 220 persons: 1600mm. These are minimum clear widths excluding projections such as door handles and radiators. In residential buildings, corridors serving fewer than 3 dwellings may be 900mm wide. All escape corridors must have emergency lighting.

What are the rules for dead-end corridors?

A dead-end corridor is a section where travel is possible in one direction only. AD B limits dead-end corridors to: 4.5m in residential buildings (flats, hotels) and 7.5m in other buildings (offices, shops). Dead-end corridors beyond these lengths require either a second escape direction, a fire-rated lobby between the dead end and the stair, or rearrangement of the layout. Dead-end conditions are a common compliance failure and a significant life safety risk.

How many staircases does a building need for fire escape?

The number of escape stairs depends on the occupancy and building height. Buildings with up to 60 occupants may have a single stair (subject to travel distance and dead-end limits). Over 60 occupants: minimum 2 stairs. Over 600: 3 stairs. Over 1000: 4 stairs. Buildings over 18m in height should have at least 2 stairs in most cases. Each stair must be protected and lead independently to a final exit. The width of each stair must be sufficient for the number of occupants it serves.

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Means of Escape Calculator

Check means of escape compliance including travel distances, corridor widths, stairway requirements, inner rooms and dead-end corridors per Approved Document B.

Building Type

Building use classification

Number of Storeys

Total above-ground storeys

Escape Direction

Number of escape directions available

Actual Travel Distance

Measured from furthest point to exit

Occupancy

Number of persons in the building

Corridor Width

Clear width of escape corridor

How We Calculate This

This calculator checks key means of escape parameters against Approved Document B requirements, covering travel distances, corridor and stairway widths, inner rooms and dead-end corridors.

How it works

Travel distance: Checked against AD B Table 2/3 based on building type and escape directions.
Corridor width: Based on occupancy served by the corridor.
Stairway: Width and number based on occupancy and building height.
Inner rooms / dead ends: Checked against AD B limits.