What travel distance means
Travel distance is the distance a person has to cover from any point in a building to reach a storey exit or a final exit. It is measured along the route someone would actually walk (around the furniture layout, around fixed obstructions, through the door openings), not as a straight line across the plan.
It is the most-checked number in a means of escape design, because it is the one a reviewer can verify with a scale rule and no assumptions. Get it wrong and the error is visible immediately.
One direction versus more than one
The limits split on a single question: from the point you are standing, can you turn your back on a fire and still get out?
- Escape in one direction only: a dead end. If the fire is between you and the exit, there is no alternative. Limits are short.
- Escape in more than one direction: alternative routes are available. To count, the routes must be genuinely independent: separated by fire-resisting construction, or at an angle such that a single fire cannot block both. Approved Document B expects the routes to diverge by at least 45 degrees, unless they are separated by construction.
A common error is claiming two directions when both routes pass through the same lobby, the same corridor node, or the same door. If a single fire can block both, it is one direction.
Approved Document B Volume 2, Table 2.1
Buildings other than dwellings. Distances in metres.
| Use of the premises | One direction (m) | More than one direction (m) |
|---|---|---|
| Residential (institutional) | 9 | 18 |
| Residential (other): within a bedroom | 9 | 18 |
| Residential (other): in bedroom corridors | 9 | 35 |
| Residential (other): elsewhere | 18 | 35 |
| Office | 18 | 45 |
| Shop and commercial | 18 | 45 |
| Assembly and recreation: buildings primarily for disabled people | 9 | 18 |
| Assembly and recreation: areas with seating in rows | 15 | 32 |
| Assembly and recreation: elsewhere | 18 | 45 |
| Industrial: normal fire risk | 25 | 45 |
| Industrial: high fire risk | 12 | 25 |
| Storage and other non-residential: normal fire risk | 25 | 45 |
| Storage and other non-residential: high fire risk | 12 | 25 |
| Place of special fire hazard | 9 | 18 |
| Plant room: within the plant room | 9 | 35 |
| Plant room: escape route not in the open air | 18 | 45 |
| Rooftop plant: escape route in the open air | 60 | 100 |
Approved Document B Volume 1: dwellings
Distances in metres.
| Situation | One direction (m) | More than one direction (m) |
|---|---|---|
| Within a flat: flat entrance door to any point in any habitable room | 9 | n/a |
| Common area: flat entrance door to a storey exit or stair lobby | 7.5 | 30 |
| Common area: small single stair building (Diagram 3.9) | 4.5 | n/a |
| Live/work unit: working area to the flat entrance door or alternative exit | 18 | n/a |
Direct distance and the two-thirds rule
Sometimes you do not know the layout. An open-plan office shell, a speculative unit, a space that will be fitted out later: there is no furniture plan to route around.
In that case Approved Document B allows direct distance to be used: the straight line from the point to the exit, ignoring the route. Because a real route is always longer than a straight line, the limit is reduced. The convention is two thirds of the travel distance limit.
direct distance limit = travel distance limit × 2 / 3Office, more than one direction: 45 m travel → 30 m direct
Office, one direction: 18 m travel → 12 m direct
Note which way the concession runs. Direct distance is a simplification that costs you a third of your allowance. If you have a real layout, measure the real route and use the full limit.
Measuring it properly
- Start at the most remote point in the space, not a convenient one. In an open-plan floor this is usually a corner.
- Route around fixed obstructions: cores, columns, fixed furniture, plant enclosures.
- Include the distance within the room as well as within the corridor. Distance inside the room of origin is the part most often forgotten.
- Stop at the storey exit: the door into the protected stair enclosure, or a final exit. The distance down the stair is not travel distance; it is dealt with separately by stair capacity.
- Check the dead-end portion separately. Where a route runs one-directionally before reaching a point of choice, that portion has to satisfy the one-direction limit even if the total route satisfies the multi-direction limit.
The mistake that costs a redesign. A floor plate is checked against the more-than-one-direction limit because two stairs are provided, but the first 20 m from the far corner runs down a single corridor before the routes diverge. That leg is a dead end and has to meet the one-direction limit. It is caught at review, and by then the core positions are fixed.
Where BS 9999 differs
BS 9999 does not use a single table per building use. It classifies the occupancy into a risk profile, combining how quickly a fire is likely to grow with the state and familiarity of the occupants, and then allows travel distances to vary with that profile and with the fire protection systems installed. In favourable cases the permitted distances are appreciably longer than the ADB equivalents.
This is a legitimate and often better-reasoned route, but the risk profile has to be justified rather than asserted, and you cannot take the BS 9999 distance while relying on ADB provisions elsewhere.
Last reviewed 25 July 2026 against the editions named above. Standards are revised; check the current published edition before relying on anything here in a design.