Part B · England · Free to use
Escape stair capacity calculator
People a stair can carry for simultaneous evacuation (Table 3.2) or the width needed for phased evacuation.
Approved Document B Volume 2, Tables 3.1 to 3.3
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Simultaneous: everyone on all storeys served. Phased: the most people on any one storey.
Part B · Result
Carries 465 people
2 stairs, 6 storeys, simultaneous evacuation.
Checks passed- People per stair, one stair discounted: Calculated result420 ÷ 1420
- Stair capacity: Checks passed1,200 mm stair serving 6 storeys (Table 3.2)465 people
- Capacity by formula: Calculated resultP = 200W + 50(W − 0.3)(N − 1)465 people
- Stair width: Checks passedmin 1,000 mm for over 50 people; 1,100 mm for assembly1,200 mm
- Where there is more than one stair, assume the largest is unavailable (para 3.17), so capacity is shared by the rest.
- Table 3.2 is read with the stair width rounded down to the nearest column; over 10 storeys extrapolate.
Clauses this relies on
Source edition and scope
Approved Document B Volume 2, Tables 3.1 to 3.3.
This is a preliminary check of the conditions shown. Confirm the edition, project circumstances and any additional requirements with your architect or building control.
A design aid, not legal advice. Checked against the Building Regulations 2010 for England; confirm with building control.