Design for Vertical Escape in Buildings

Vertical escape routes
These are provided by protected escape stairs of sufficient number and adequate size. Generally, the rules requiring alternative means of escape mean that more than one stairway is required. The width of the stairs should allow the total number of people in the storey or building subjected to fire to escape safely. Wide stairways must be divided by a central handrail. The width should be at least that of the exits serving it, and it should not reduce in width as it approaches the final exit.

Typical minimum escape stair widths, depending on the type of building and the number of people they serve, are as follows: 1000 mm for institutional buildings serving up to 150 people; 1100 mm for assembly buildings serving up to 220 people; between 1100 mm and 1800 mm for any other building serving more than 220 people, depending on the number of people and number of floors.

 

Each internal escape stair should be contained in its own fire-resisting enclosure and should discharge either directly, or by means of a protected passageway, to a final exit. As protected stairways must be maintained as a place of relative safety, they should not contain potentially hazardous equipment or materials. These restrictions do however allow the inclusion of sanitary facilities, a lift well, a small enquiry office or reception desk, fire protected cupboards and gas meters.

 

Reductions in the level of fire resistance are allowed on the outside wall of a staircase, depending on the proximity to other openings in the facade.

Basement stairs need special attention. The danger of hot gases and smoke entering the stair and endangering upper storeys means that at least one stair from the upper storeys should not continue down to the basement. In continuous stairs, a ventilated lobby should separate the basement section from the section serving the upper floors.

External escape stairs are usually permissible as an alternative means of escape, but should be adequately protected from the weather and fire from the building. They are not suitable for use by members of the public in assembly and recreation buildings.

 

Access for Firefighters
Provision should be made in design to allow firefighters good access to the building in the event of a fire, and to provide facilities to assist them in protecting life and property.

Sufficient access to the site for vehicles must be provided to allow fire appliances to approach the building. Principal appliances are ladders, hydraulic platforms and pumping appliances. Access roads for fire appliances should be at least 3.7 m wide with gates no less than 3.1 m. Headroom of 3.7 m for pumps and 4.0 m for high-reach appliances is required. The respective turning circles of these appliances are 17 m and 26 m between curbs. Allow 5.5 m wide hardstanding adjacent to the building, as level as possible (not more than 1 :12), with a clearance zone of 2.2 m to allow for the swing of the hydraulic platform.

Firefighters must be able to gain access to the building. The normal escape routes are sufficient in small and low buildings, but in high buildings and those with deep basements additional facilities such as firefighting lifts, stairs and lobbies, contained within protected shafts, will be required.

 

Fire mains in multistorey buildings must be provided. These may be wet or dry risers (fallers in basements).

A means of venting basements to disperse heat and smoke must be provided. In basements, flames, gases and smoke tend to escape via stairways, making it difficult for firefighters to gain access to the fire. Smoke vents (or outlets) are needed to provide an alternative escape route for these emissions directly to the outside air and allow the ingress of cooler air. Regulations stipulate the positions and sizes of vents. Either natural venting or mechanical venting in association with a sprinkler system may be used.

 

Taken from: Architects’ Data by Ernst and Peter Neufert

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