## Floor loading occupancy calculator

Calculations behind our poster "occupancy by discipline" can be explored with the calculator below. The default values in the calculator below will result in an "**occupancy**" of **85,500**, as per the poster. This is a value that you may wish to challenge, and we encourage you to do this!

For example, you might:

- Add an allowance for "non-human items" (a typical value for desks, chairs, paperwork, and plants might be 0.50kN/m2 - approximately 50kg/m2, which is the same as two bags of cement per square metre, or 20 reams (10,000 sheets) of A4 paper per square metre).
- Add an allowance for partitions (normally added on top of the imposed floor loading, for example you might have a total Imposed Floor Load = 3.5kN/m2, made up of 2.5kN/m2 + 1.0kN/m2 for partitions)
- Change the utilisation factor from 1.00 (
**assumed here, see note 3**) to 0.80 (commonly assumed by designers). - Change the weight of your humans (0.75kN average is assumed here)

**Note 1**: In the calculations we assume 95% of the floor area is loaded to the value your provide. In the UK it is standard practice to apply a higher floor load of around 7.5kN/m2 over the remaining 5% of floor area. We do not consider this in the calculation of occupancy.

**Note 2**: The "Total Imposed Floor Load value" entered here should include any allowance for partitions and non-human items. So, if you have a floor load specification of 2.5kN/m2 + 1.0kN/m2 you would enter 3.5kN/m2 in the "Total" row. Below that, you enter 1.0 as the partition load. And below that you choose some value of the 2.5kN/m2 that you want to allocate to "non-human items".

**Note 3: **BS EN 1991-1-1 allows for columns and walls that the total imposed loads from several storeys may be multiplied by a reduction factor. This is calculated in different ways in different countries, but gives a number normally between 0.50 and 1.00. In the calculation below, you could imagine you are designing the ground floor column. As an example for the UK, a 30,000m2 structure with 16 storeys would give a reduction factor of 0.50 for the ground floor column.

**Note 4**: The Utilisation Factor is the value chosen by the designer as a ratio between actual performance value and the maximum allowable performance value which is deemed limiting for a structural member. For Eurocodes, this is the ratio between "Ed" and "Rd". In the UK it is normally taken by designers as 0.80. In the poster, we have assumed a **Utilisation of 1.00 **(**i.e. Ed = Rd)**. A utilisation factor of 1.00 is safe - see BS EN 1990, e.g. Equation 6.8 for equilibrium at the ULS, or Equation 6.13 for SLS.