Single staircase and travel distance in a worker dormitory conversion
A four-storey composite building in Yau Ma Tei has ground-floor shops and three upper floors, each 450 m², formerly used as offices. The owner proposes converting the upper floors into a 60-bed worker dormitory, 20 beds per floor, with a single 1.2 m wide staircase serving all floors. The staircase is open to each floor corridor; there is no protected lobby. The farthest bed is 22 m from the staircase door, and the corridor is 1.5 m wide with a dead-end section of 8 m. The ground-floor exit discharges into a 3 m wide covered alley that is also used for refuse storage. The project architect argues that because each floor has only 20 occupants, the single staircase is acceptable under the Code of Practice. The client wants to start fitting-out next month. The building is also subject to a Fire Safety (Buildings) Ordinance direction for improvement.
1. Assess the architect's single-staircase argument. Identify which aspects may be acceptable and which are not, and state the code and statutory issues you would raise.
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The architect has applied only the floor-area and occupant-capacity screening rule. A single staircase is often permitted where the floor area does not exceed about 500 m² and the occupant capacity does not exceed about 50 per floor, so 450 m² and 20 beds may pass that first test. That does not make the design compliant.
The critical issues are:
- Travel distance. The farthest bed is 22 m from the staircase. For a single-staircase, single-direction escape, the Code limit is much shorter - commonly 15 m for non-domestic and 18 m for domestic premises, subject to the current table. A 22 m distance with an 8 m dead-end section is not acceptable without a second route or a performance-based justification.
- Staircase protection. The staircase is open to every corridor and has no protected lobby. It must be enclosed in fire-resisting construction with self-closing fire doors; a dormitory sleeping risk may also require a protected lobby and smoke control.
- Discharge. The exit discharges into a 3 m alley used for refuse storage. That is an obstructed and combustible escape route and is not a satisfactory final exit.
- Change of use and statutory approval. The conversion changes the use and occupancy; it needs Building Ordinance approval, a means-of-escape submission and compliance with the Fire Safety (Buildings) Ordinance direction. The FSB direction cannot be left to the fitting-out stage.
The 'only 20 occupants' argument is not a defence: occupant number affects staircase width and capacity, not the single-direction travel-distance and protection requirements.
2. Set out a practical package of measures and the approval route you would recommend to the client, including whether a performance-based alternative is appropriate.
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Recommended package:
- Geometry: provide a second means of escape or rearrange the beds so that no bed exceeds the permitted single-direction travel distance; eliminate the 8 m dead end by forming a cross-corridor or a second exit.
- Staircase: enclose the staircase with the required fire resistance period, fit self-closing fire doors, and provide a protected lobby if the Code or risk assessment requires it. Do not accept doors wedged open; fit hold-open devices linked to the alarm.
- Smoke control: consider lobby pressurization or a smoke shaft for the staircase, especially if a single staircase is retained.
- Discharge: relocate or clear the alley, remove refuse storage, and provide a direct, unobstructed route to a street or open air.
- Detection and alarm: provide automatic detection in beds, corridors and communal areas, with sounders in all beds; consider a monitored link to a central station.
Approval route: submit amended plans to the Buildings Department and the Fire Services Department; respond to the FSB direction; do not start fitting-out on the basis of the architect's assurance. A performance-based alternative can be considered, but it must demonstrate ASET > RSET for the single-staircase case, including a fire in a bedroom, door-opening effects and smoke spread into the corridor. It must be peer-reviewed and accepted by the approving authority; it is not a substitute for the prescriptive requirements unless the authority agrees.