Guide to assessing your occupancy limit

Understanding the maximum occupancy of your premises (the number of people that can fit inside safely) is an important part of your fire risk assessment, but can be challenging if you’re not used to it. We’ve created a stripped back guide to working this out, based on government guidance.

Please watch this short guide.

Please note that this video is a basic guide to calculating the occupancy limits in simple licensed premises, it is not for complex or multi storey premises. If your premises is complex or if your premises falls outside of the scope of the video, then you should consult the relevant government guidance as detailed in the video, use another fire safety standard / guidance document or seek the advice of a competent fire risk assessor.

This information is taken from the Home Office’s fire risk assessment guides and the Approved Document B of the Building Regulations and will be sufficient for simple premises. If your needs are more complex it may be necessary for you to consult a fire risk assessor.

There are two factors that will limit the safe occupancy of your premises:

• The floor space factor, or how many people can you fit into the space; and
• The escape route capacity, or how many people can evacuate from your building in a safe period of time

Floor Space Factor

Different premises, or different areas within the same premises, need to do different things – you can’t fit as many people onto a factory floor as you can a dance floor. The amount of space each person will take up in various types of premises has been worked out in the  Approved Document B.

To work out the number of people that your floor area can safely accommodate first divide the premises up into distinct spaces, based on how they are used. The easiest way to do this is by using a plan drawing.

• Create a rough plan of your building, dividing up areas based on how they are used. Don’t include stairs or exit routes, we want to keep those clear. Similarly, don’t include toilets or storage rooms where you don’t expect people to be spending most of their time.
• Work out the area of each of these spaces in m²
• If you have more complex needs you may need to refer to the above guides
• If you don’t find a usage type that looks right to you then consult the more detailed table of floor space factors. Where you have a space which is used for multiple functions you should apply highest floor space factor, i.e. the largest amount of space per person.

Divide the area of each space by the appropriate floor space factor, or to make it easier use our floorspace calculator.

Exit Capacity

Now we need to work out how to get these people out safely. Here you are limited by the number and width of routes out of the building. Measure the narrowest point along each of these routes, which will probably be a door. Unless you have fewer than 5 people likely to use an exit it needs to be a minimum of 750mm wide, or 900mm for wheelchair users. 750mm can accommodate 100 people, a 1050mm can accommodate 200. If you have a door wider than 1050mm then for every 5mm over 1050mm you can add another person.

If you only have one exit out then your total occupancy is capped at 60 people.

If along your exit route you have a door which opens inwards, or against the flow of people out of the building, that’s capped at 60 people too. Note that this limit might not apply if the door is held open.

Because we want to make sure that we are allowing for a safe number of people when there’s a fire, we need to make sure that everything still holds up under the worst case fire condition. To do this, we look at the total number of people that each route out of the building can accommodate and discount the highest one. That way, even if a fire made that way out completely inaccessible we would still be able to safely exit using the rest of the exits. For the same reason, if two exits are close enough together that a single fire could reasonably make them both inaccessible then we count them as a single exit for occupancy purposes.

Add these together (apart from the one you’ve discounted) to find your total exit capacity, or to make it easier out all of your exit widths into our exit capacity calculator.

Occupancy Limit

So now we know how many people can safely fit inside your premises, and how many people can safely get out of your premises. The total safe number of occupants for your premises is the lowest of those two numbers.

Don’t forget that in more complex buildings it might not be quite so simple – maybe your layout does not let everybody get to every exit, for example. For more information on how to deal with more complicated arrangements you might need to spend some time with the guidance, or it may be appropriate to talk to a professional about your fire risk assessment.