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Escape Provision Computation

Farid Akashah, Ph.D, MRISM

faridakashah@um.edu.my

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Computing Number of Staircases and

Staircases Width

5-storey residential building

Which purpose group?

Each level designed as a compartment

Floor areas: Ground Floor to Level 3: 1600 m2

Level 4: 1800 m2

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Staircase exit width calc. table1 Level GF 1 2 3 4

2 Purpose Group, Occupancy Load III, 20 III, 20 III, 20 III, 20 III/20

3 Floor Area (m2) 1600 1600 1600 1600 1800

4 Occupancy* = Floor Area /

Occupancy Load

80 80 80 80 90

5 Exit Capacity Required for Stairs= Occupancy/No of persons per

unit for Stairs

1.8 1.8 1.8 1.8 2.0

6 Minimum Staircase Width (mm)

= Exit Capacity Required for

Stairs * 550 mm

990 990 990 990 1100

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Notes

Purpose Group Fifth Schedule, UBBL 1984

Occupant Load 2nd Column of SeventhSchedule, check whether areas to be used isnett or ross

Exit Capacity 3rd 6th Column of SeventhSchedule, establish type of exit and exitcapacity that is appropriate e.g. doors outside,

horizontal exit, ramp main exit, rampsecondary exit, escalator or stairs

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Making sense of the table (1/5)

Referring to Row 6 in the earlier slide, Level 4

is the largest in terms of floor area and theexit width (staircase) required is 1100mm.

requirement.

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Making sense of the table (2/5)

By-laws 168 and 177 of UBBL 1984 stipulate

that every upper floor shall have means ofegress via at least two separate staircase

-

single staircase), assuming exit distances are

complied with. A minimum of two staircases

are therefore required for compliance.

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Making sense of the table (3/5)

In such calculation, assumption that one of

the protected staircases is inaccessible is to bemade. In reference to the table presented in

,

provided, they would therefore each have to

be minimum of 1100mm width to cater for

the occupant load.

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Making sense of the table (4/5)

Three-staircase scenario

If three staircases were provided say main

staircase/fire fighting staircase width of 1200mm

minimum 1100mm 550 mm width door and

two secondary staircase of 900mm width each.The check would be as follows:

Total exit width:

Main staircase 1200 mm

Secondary staircase 1 900 mm

Secondary staircase 2 900 mm

TOTAL EXIT WIDTH 3000 mm

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Making sense of the table (5/5) Three-staircase scenario

Total exit width:Main staircase 1200 mm

Secondary staircase 1 900 mm

Assuming the widest staircase (main staircase) isinaccessible, remaining exit width is:

3000 mm 1200 mm = 1800mm 1800 mm > 1100mm, therefore the provision satisfies the

By-laws.

TOTAL EXIT WIDTH 3000 mm

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References

Abu Bakar, H. (ed) 2008, Guide to Fire

Protection in Malaysia, The Institution of FireEngineers (UK) Malaysia Branch, Kuala

.

Uniform Building By-Laws 1984