Last edited 31 May 2021

Floor area ratio

The floor area ratio (FAR), also known as the plot ratio, is a measure of the total permitted floor area of a building, in relation to the total area of the lot (or plot) on which the building stands:

Gross floor area of all floors of the building / Area of the building lot = FAR

A higher ratio indicates a higher-density environment.

The concept emerged in Europe in the 19th century, and was then taken up in the USA in the 20th century as a form of zoning control for rapidly developing cities. FAR is now often used by urban planners, particularly in the USA, for assessing, or restricting, planning permissions, setting a limit on the 'load factor' generated by new developments, beyond which undue stress is placed on a city and its infrastructure.

A low permitted FAR may deter development, whilst a higher FAR allows more usable area, and hence higher potential sales.

The same FAR value can be achieved by buildings with varying numbers of storeys. For example:

1,000 sq. m building with one storey / 4,000 sq. m lot = 0.25

500 sq. m building with two storeys / 4,000 sq. m lot = 0.25

An FAR of 1.0 allows the developer to build a one-storey building over the lot, or a two-storey building over half the lot, or a three-storey building over one-third of the lot, and so on.

An FAR of 2.0 allows the developer to build a two-storey building over the lot, or a four-storey building over half, and so on.

Bradford City Centre Design Guide, Supplementary Planning Document, published in 2006, defines plot ratio as: ‘A measure of density for non-residential use. This is expressed as a ratio in which the first number relates to the floor area of the building and the second to the area of the site. A 2:1 ratio therefore denotes a building that has two times the floor area of the site. This could be a two storey building covering the entire site or a four storey building covering half of the site.’

NB Land measurement for planning and development purposes, Guidance Note, Global 1st edition, Published by the Royal Institution of Chartered Surveyors (RICS) in May 2021, defines plot ratio (PR) as: ‘…the ratio of total development floor area to site area. Development floor area may be measured as gross external area (GEA) or gross internal area (GIA), but whichever is used – or modifications of them – should be clearly stated. Gross external area and gross internal area are defined in Property measurement, RICS professional statement.’ It suggests that floor area ratio (FAR) and floorspace ratio (FSR) are similar terms.

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