Last edited 28 May 2019

Floor loading

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Floors must be capable of bearing loads applied to them. There are two main types of load - live loads and dead loads:

Dead loads include the weight of the building materials themselves, and are static and permanent. The dead load value is determined by adding together the weight of all permanently installed materials.
Live loads are imposed on the building and are temporary and dynamic, such as the weight of occupants, furniture or anything else that can be moved.

To determine the minimum design values for strength, live and dead loads are added together.

In order to resist these loads, all elements of the floor must have the requisite strength and stiffness, typically determined by the maximum allowable deflection of the floor, i.e. how much, it will 'bend' under the maximum expected load.

Determining dead loads is relatively straight forward, however as live loads are changeable structural designs can only make a reasonable allowance for what is expected.

Allowing for higher live loads increases the flexibility of a building, but also increases the cost. For example, historically, UK office buildings have been designed and marketed with live loadings of 3.5–4.0 kN/m2, however, this may be an over-provision. 2.5 kN/m2 for floors above ground floor and 3.0 kN/m2 at, or below, ground floor over may be more appropriate, with 7.5 kN/m2 over 5% of the floor area to allow for future flexibility.

See Structural systems for offices for more information.

There may be particular problems in older buildings which have been adapted for modern uses, resulting in live loads that are far higher than was allowed for by the original design. For example, historic houses converted to office use where there may be very high storage or equipment loads.