Fire Escape Route Calculator — Check Compliance with Approved Document B

No. Approved Document B Volume 1 does not control a single dwellinghouse with a horizontal travel-distance figure — it controls by storey height. A house with a floor more than 4.5 m above ground level must have a protected stairway running the full height of the building; a two-storey house up to 7.5 m can instead rely on escape windows to first-floor habitable rooms (clear openable area at least 0.33 m², at least 450 mm high and 450 mm wide, cill no more than 1100 mm above the floor). The widely-quoted 9 m figure is the FLAT internal limit (door of any habitable room to the flat entrance door, single direction), not a house limit.

There are two separate limits. Within an individual flat, the maximum travel distance from any point in any habitable room to the flat entrance door is 9 m (Approved Document B Volume 1, paragraph 3.18 and Diagram 3.3) — this is a single maximum and does not have a more-permissive "alternative directions" variant. In the common corridor outside the flats (AD B Vol 1 Table 3.1), escape in one direction only (a dead end) is limited to 7.5 m, extending to 30 m where escape is possible in more than one direction. Distances are measured along the actual route, not in a straight line.

In a dwellinghouse with a floor more than 4.5m above ground (3 or more storeys, including a loft conversion), fire doorsets are required to the habitable rooms that open onto the protected stairway (hallway, landing and stairway), and the stairway must be enclosed as a protected route from top to bottom. The minimum is E 20 (FD20), not FD30: Approved Document B Vol 1 Table C1 item 11(b) rates a door forming part of the enclosures to a protected stairway in a single family dwellinghouse at E 20, and the E 30 Sa (FD30S) entry at item 4a expressly excepts that case, so no cold smoke seal is required. Appendix C para C5c also exempts fire doorsets within a dwellinghouse from self-closing devices, so no closer is needed on those doors; the door between the house and an integral garage is the one that does need FD30S with a closer. E 20 is the current requirement and only the product changed: FD20 doorsets are no longer third-party certified, so an FD30 door is what you buy to satisfy the E 20 minimum.

Flat entrance doors must be FD30S — a 30-minute fire door with cold-smoke seals (the S suffix indicates smoke seals). This applies to all flats regardless of the number of storeys, and the door must be fitted with a self-closing device so it shuts automatically.

For common escape routes in buildings other than dwellings (the relevant rule for flats and HMOs), Approved Document B Volume 2 sets the minimum clear width by the number of people it serves: up to 60 persons 750 mm, up to 110 persons 850 mm, up to 220 persons 1050 mm, and over 220 persons 5 mm per person (never less than 1050 mm). For example, a route for 300 people needs 300 × 5 = 1500 mm. These are non-dwelling provisions and do not apply inside a single house, where the hallway/landing simply needs to be a usable protected route.

An HMO (House in Multiple Occupation) is a property rented to 3 or more people forming 2 or more households who share facilities. HMO fire safety is risk-assessed using the LACORS Housing — Fire Safety Guidance (2008): a 9 m single-direction travel distance is treated as a benchmark beyond which additional risk should be assessed and mitigated, rather than an absolute pass/fail limit. Typical provisions include FD30S fire doors to bedrooms and kitchens, a Grade D LD2 interlinked smoke and heat alarm system, and emergency lighting in common areas.