Technical Booklet E Fire Safety·Page 63·Worked examples (b)(i)
Worked Example: Stair Width Calculation for 12-Storey Office Building with Uneven Population Distribution - Upper Floors
Demonstrates stair width calculation for upper floors (10-11) in a 12-storey office building with 200 people, requiring minimum width of 1100 mm despite formula result being smaller.
To find the width of the stairs serving floors 10 to 11 –
P = 200/2 = 100, n = 2
From the formula –
100 = 200w + 50(w - 0.3)(2 - 1)
100 = 200w + (50w - 15)(1)
100 = 200w + 50w - 15
115 = 250w
w = 0.46 m (460 mm)
Therefore, both stairs between the 9th floor landing and the top floor should be at least 460 mm. But this needs to be increased to 1100 mm as the formula applies to stairs 1100 mm or wider (see paragraph 2.65).
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