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.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
How much does it cost to build a house?
A brief run down of key considerations from a London based practice.
The need for a National construction careers campaign
Highlighted by CIOB to cut unemployment, reduce skills gap and deliver on housing and infrastructure ambitions.
AI-Driven automation; reducing time, enhancing compliance
Sustainability; not just compliance but rethinking design, material selection, and the supply chains to support them.
Climate Resilience and Adaptation In the Built Environment
New CIOB Technical Information Sheet by Colin Booth, Professor of Smart and Sustainable Infrastructure.
Turning Enquiries into Profitable Construction Projects
Founder of Develop Coaching and author of Building Your Future; Greg Wilkes shares his insights.
IHBC Signpost: Poetry from concrete
Scotland’s fascinating historic concrete and brutalist architecture with the Engine Shed.
Demonstrating that apprenticeships work for business, people and Scotland’s economy.
Scottish parents prioritise construction and apprenticeships
CIOB data released for Scottish Apprenticeship Week shows construction as top potential career path.
From a Green to a White Paper and the proposal of a General Safety Requirement for construction products.
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherited assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.
The 2025 draft NPPF in brief with indicative responses
Local verses National and suitable verses sustainable: Consultation open for just over one week.
Increased vigilance on VAT Domestic Reverse Charge
HMRC bearing down with increasing force on construction consultant says.
Call for greater recognition of professional standards
Chartered bodies representing more than 1.5 million individuals have written to the UK Government.