Last edited 29 Oct 2020

Functional unit of buildings

The New Rules of Measurement (NRM) are published by the Royal Institute of Chartered Surveyors (RICS). They provide a standard set of measurement rules for estimating, cost planning, procurement and whole-life costing for construction projects.

According to NRM1: Order of cost estimating and cost planning for capital building work, a functional unit is:

‘…a unit of measurement used to represent the prime use of a building or part of a building (e.g. per bed space, per house and per m2 of retail area). It also includes all associated circulation space.'

NRM1 defines the functional unit method as:

‘…a rough budget-setting technique which consists of selecting a suitable standard functional unit of use for the project, and multiplying the projected number of units by an appropriate cost per functional unit.’

NB BRE's Environmental impact of biomaterials and biomass defines a functional unit as:

'...a qualitative description of function specifically defined for the product/service under study and any alternative product/services to which it is compared. The use of a functional unit means that the alternative designs under study are, in theory, compared fairly. For example, a comparison of external walls may be based on every external wall design in the study achieving a U-value of 0.3 W/m²K and compliance with building regulations.'

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