Widths of stairs

The Regulations in Section K no longer have specific rules on the widths of stairs, but Section B for fire safety and Section M for access and facilities for the disabled specify some minimum widths. The practical problems of handling furniture need to be considered, tight turns can restrict the movement. Access to bathrooms and WCs can be reduced to 600 mm.

Section B, Fire Regulations and Section

M, Disabled Facilities have restrictions. The key dimensions for stair widths are given as follows.

• The narrowest permitted escape stair is 800 mm.

• Common stairs in flats have to be 1 000 mm but 1100 mm if they are fire fighting stairs.

• A stair serving an assembly building has to be 1 000 mm unless the area served is less than 100 m2.

• Stairs that are wider than 1 800 mm in assembly buildings have to be divided by guard rails.

• Stair widths are measured at 1 500 mm height.

• The widths depend upon the number of persons in the building (Figure 10.1 i).

• The Regulations assume that in buildings with two escape routes one will be disabled by fire. The widths for each stair have to conform with the tables (Figures 10.1 i and 10.1/) since either may have to take the full traffic load in an emergency.

Maximum number Minimum width of persons (mm)

5.0 8003

110 900

220 1100

more than 220 5 per person

Figure 10.li Widths o/ escape routes and exit

Maximum number of people in any storey

Stair width1 (mm)

100

1000

120

1100

130

1200

140

1300

150

1400

160

1500

170

1600

180

1700

190

1. Stairs with a rise of more than 30 m should not be wider than 1400 mm unless provided with a central handrail (see para 4.6 [p.7.55]).

2. As an alternative to using this table, provided that the minimum width of a stair is at least 1000 mm, the width may be calculated from: (PxlO) -.100] mm where P = the number of people on the most heavily occupied storey.

Notes:

1. Stairs with a rise of more than 30 m should not be wider than 1400 mm unless provided with a central handrail (see para 4.6 [p.7.55]).

2. As an alternative to using this table, provided that the minimum width of a stair is at least 1000 mm, the width may be calculated from: (PxlO) -.100] mm where P = the number of people on the most heavily occupied storey.

Figure 10.1j General requirements under Section K: Minimum aggregate width of stairs designed for phased evacuation

• Long flights over 30 m in descent to be 1400 mm maximum width, which implies a total traffic limit of 700 persons per stair.

• Stairs over 1 400 mm wide may have to jump to 1800 mm wide to comply with the central guard-rail rule.

• Phased evacuation permits narrower stairs since safe collection points have to be provided at various floor locations in the height of the building (Figure 10.1/). In buildings planned for phased evacuation each floor must be a compartment floor, stairs must relate to a protected lobby or passage approach, a fire warning system and intercom is needed between fire wardens (floor by floor) and a control point. Sprinklers are required throughout buildings which exceed 30 m in height.

• Stairs used for means of escape in case of fire must exit direct to the open air.

• The Regulations permit strings and handrails to project into the stair width (Figure 10.1k).

The Regulations are very specific about forms of lifts and stairs that are not acceptable as means of escape in case of fire.

• Lifts unless evacuation lifts.

• Portable or throwaway ladders.

• Escalators (though travelators are accepted if switched off in case of fire).

• Accommodation stairs (except for small shops with a total area of all floors less than 90 m2 and limited to basement, ground and first floor level).

0 0

Post a comment