Fire Escape Distance Calculator

Under Approved Document B Volume 2 (Table 2.1), the maximum travel distance in an office is 18m where escape is possible in one direction only (a dead end) and 45m where travel is possible in two or more directions. These limits are fixed — AD B does not increase them where a sprinkler system is fitted.

The same ones this calculator already gives for flats, because Approved Document B sets travel distance by where you are, not by how tall the building is. Within a flat the limit is 9m to the flat entrance door (Volume 1, paragraph 3.18 b(i) and Diagram 3.3). In the common areas the limits are 7.5m where escape is possible in one direction only and 30m where escape is possible in more than one direction (Volume 1, Table 3.1). A small single stair block serving no more than two flats per storey is 4.5m (Diagram 3.9). Choose "Common areas of flats" or "Within a flat" above and the calculator applies these. What does change as a block gets taller is other provision rather than travel distance: a sprinkler system is required above 11m, and compartmentation periods step up with the height of the top storey. Those are separate requirements and this calculator does not assess them.

Travel distance is measured along the actual path of travel from any point in the room to the nearest storey exit, following the route a person would walk — not a straight line. Furniture and obstructions must be considered. The distance includes travel within the room and along corridors. If the internal layout is not known, AD B allows the direct (straight-line) distance to be used and assumed to be two-thirds of the actual travel distance.

A dead end occurs when escape is possible in only one direction from a point in the building. This is the most restrictive condition, with shorter maximum travel distances, because occupants have no alternative route if their escape path is blocked by fire. Two escape routes only count as alternatives if they are at least 45 degrees apart, or are separated by fire-resisting construction (AD B Vol 2 para 2.10).

No. The travel distances in AD B Volume 2 Table 2.1 are fixed and do not change when a sprinkler system is fitted. The only sprinkler-related variations in this part of AD B (para 2.46) relate to residential care homes — bedroom doorset self-closers and bed counts — not travel distance. Extending travel distances on the basis of sprinklers is a risk-based engineered approach under BS 9999, which is a separate methodology requiring a competent fire engineer; it is not an automatic Approved Document B allowance.

An inner room is one from which escape is possible only by passing through another room (the access room). Under AD B Vol 2 para 2.11, the travel distance from any point in the inner room to the exits from the access room must not exceed the relevant one-direction limit in Table 2.1 for that building use (for example 18m in an office). The inner room must not be a bedroom, and the access room must not be a place of special fire hazard and must give early warning of fire (a vision panel, a gap below the ceiling, or an automatic fire detection and alarm system).