During emergencies, most school buildings and educational facilities in India appear to be critical at staircases- many appear structurally questionable, as well as like bottlenecks to an otherwise safe passage.
The National Building Code (NBC) by Bureau of Indian Standards (BIS), also known as
SP-7:2005 contains useful clauses on staircases, which apply to educational buildings, and are implementable across the country. We have extracted some information and have simplified it. The following information can be used as a checklist also.
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Design from a particular floor to evacuate in 2.5 min (Type 1), 1.5 min (Type 2), 1 min (Type 3), Not specified for Type 4
For buildings greater than 15 m height and 500 m2 in each floor:
o Minimum 2 staircases
o These should be of enclosed type
o At least one staircase on exterior wall as a facility outside also
Exit doors:
o No exit doorway to be less than 1000mm in width
o Exit doors to open outward
o Exit door shall not open immediately upon a flight of stairs, a landing equal to at least the width of the door shall be provided in the stairway at each doorway; the level of landing shall be the same as that of the floor which it serves
o Exit doorways shall open from the side, to serve without the use of a key
Where stairways discharge through corridor and passage ways, the height of corridors and passage ways shall not be less than 2.4m
Ensure all means of exit, such as lobbies, passages, staircases are well-ventilated
Internal staircases should:
o be of non combustible material
o be a self contained unit, enclosed, and with one side made of external wall
o not be arranged around a lift shaft
o not be of hollow combustible construction
o not have gas piping or electrical panels along the stairway
o can have ducting if it provides 1hour of fire rating.
o have dimensions of:
- minimum staircase width = 1.5 m
- minimum tread width = 300mm
- maximum riser height = 150mm
- maximum 15 risers per flight
- handrail height = 1.0m
- minimum head room = 2.2m
o one flight between landings shall be designed for maximum number of people occupying that floor
o not have any fire risk spaces opening directly on to staircase
o have their external exit door at ground level, and should open directly to open spaces, or large lobby, if necessary
o Main stairs to be continuous from ground to terrace
o Should not have any combustible decoration
o have clearly visible Exit signs
o show individual floors
Pressurization of staircases should be thought of, which means that although fire spread is controlled by compartmentalization of staircases in design, ingress of smoke and toxic gasses perhaps cannot be avoided. Exclusion of smoke and toxic gases from protected route is important for safe passage. Therefore, in high rise buildings air can be injected in order to raise the pressure of the stair compartment.
External staircases are desirable for high rise buildings, and when provided shall comply to the following:
o All external staircases should be directly connected to ground
o Entrance to external staircase shall be separate and remote from internal staircase
o No door or window opening shutter shall obstruct the staircase
o Should be kept in sound operable conditions
o Should be kept obstruction free
o The external staircase shall be constructed of non combustible materials, and any doorway leading to it shall have the required fire resistance
o No external staircase, used as a fire escape, shall be inclined at an angle greater than 45 deg. From the horizontal
o Some dimensions
- Staircase flight width = 1250mm
- Minimum tread = 250mm
- Maximum riser = 190mm
- Maximum risers per flight = 15
o Spiral staircase can be employed but should be
- limited to a building not higher than 9m
- designed for a low occupant load
- not less than 1500 in diameter
- designed for an adequate headroom
The above are points directly quoted by the Indian National Building Code, and should be useful in designing safer staircases for evacuation in educational buildings.
Some clauses in the code, like this one, need changing. Improvements are endless and like other international codes can be issued as amendments.
