Technical Booklet E Fire Safety·Page 64·2.65(ii)
Stair width calculation example for floors 1-9
Worked example showing how to calculate that stairs serving floors 1 to 9 should be at least 1200 mm wide using the formula from Table 2.4, ensuring adequate width when one storey exit is discounted.
To find the width of the stairs serving floors 1 to 9 –
P = 1200/2 = 600, n = 9
From the formula:
600 = 200w + 50 (w - 0.3) (9 - 1)
600 = 200w + (50w - 15) (8)
600 = 200w + 400w - 120
720 = 600w
w = 1.20 m (1200 mm)
Therefore, both stairs between the 9th floor landing and the ground floor should be at least 1200 mm wide.
This width should also be adequate to comply with paragraph 2.63 when one storey exit is discounted in accordance with paragraph 2.52 (i.e. the stair widths are not less than the minimum widths needed for 111 people in Table 2.4).
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet E - Fire Safety.pdf