Calculation for Capacity of School Halls

The occupancy figure for any building is based on the calculations below and the schools risk assessment to safely evacuate in less than 2 minutes 30 seconds.

1. The number of persons who can safely reside in the premises. Using the floor space factor below will assist in working this out. Number of people = Floor area (m²) / Occupant density
2. The width and capacity of the exit routes to allow people to escape safely. (Route capacity)
3. Seating and gangway occupancy taking into account the measurements to be adhered to below.

11.1     Floor Area Metres Squared

How to work out floor area and the maximum number of people for a completely clear floor area the maximum number is calculated based on 0.5 square metres per person.

Therefore, a hall of 20 meters X 10 meters= 200 square meters would be physically capable of holding 400 people.  If there are tables and chairs the number of people would need to be reduced accordingly and would be in the region of 1 to 1.5 square meters per person depending on the amount of seating and tables to be provided

11.2     Width and capacity of escape routes

Minimum width for an escape route should ideally be 1050 but in any case not less than 750mm and where wheelchair users are likely to use it not less than 900mm. The premises fire risk level will be obtained from the fire risk assessment.

The largest exit is taken out of the equation.

If escape route doors are too close to one another and are likely to be simultaneously disabled by the same fire (e.g. within 45° of each other) then they should be classed as one exit and it may be necessary to discount them both from your calculation. Escape routes that may be classed as ‘true alternatives’ should therefore be more than 45° apart when viewed from the furthest point in the room.

Doors can be counted as 2 exits         

Doors must be counted as one exit

Note: An occupancy limit of 60 persons will apply where only one exit exists and 60 persons is the limit for an exit where an exit door opens inwards (unless that door is fastened open).

11.3     Seating and gangways occupancy

The type of seating arrangements adopted will vary depending on the use of the hall.

Seating and gangways in a hall or assembly space should be arranged to allow free and ready access direct to the exits. Persons seated in rows will first have to make their way to the end of the row before being able to use the escape routes provided. Seating and gangways in a school premises should therefore be arranged to allow free and ready access direct to the exits.

Where rows of seats are not fixed to the floor nor do they have arms, there should be a minimum of 450mm between the back of the seat and the front of the one immediately behind it.

Gangways should be adequate for the number of seats served and at least 1.05m wide. There should be no projections which diminish these widths.

In general, no seat should be more than seven seats away from a gangway. If temporary seating is provided, these should be secured in lengths no fewer than four seats (and no more than 12). This can be achieved using plastic cable ties around the legs of adjacent chairs.

Standing and sitting in gangways, or in front of any exit, should not be permitted. This includes adults standing by children.

The way to calculate out occupancy is for a member of staff to set up the area taking into account of the measurements above. This will determine the occupancy level of the room.

Staff in charge need to communicate at the start of productions that should the alarm sound they will take responsibility for safe evacuation of the pupils and outline what measures will need be taken in the event of an evacuation.

Seating and Gangways

FD- Fire Door