Floor area ratio

Floor area ratio (FAR) is the ratio of a building's total floor area (gross floor area) to the size of the piece of land upon which it is built. The terms can also refer to limits imposed on such a ratio.

As a formula: Floor area ratio = (total covered area on all floors of all buildings on a certain plot, gross floor area) / (area of the plot)

History

One of the purposes of the 1916 zoning ordinance of New York City was to prevent tall buildings from obstructing too much light and air. The 1916 zoning ordinance sought to control building size by regulating height and setback requirements for towers. In 1961, a revision to the zoning ordinance introduced the concept of floor area ratio (FAR).

Purpose

The floor area ratio (FAR) can be used in zoning to limit the number of people that a building can hold instead of controlling a building's external shape.

For example, if lot must adhere to a 0.10 FAR, then the total area of all floors in all buildings on the lot must be no more than one-tenth the area of the parcel itself. (In other words, if the lot was 10,000 sq. ft, then the total floor area of all floors in all buildings mustn't exceed 1,000 sq. ft.)

Common exclusions to the total calculation of square footage for the purpose of floor area ratio (FAR) include unoccupied areas such as mechanical equipment floors, basements, stair towers, elevator shafts, and parking garages.

An architect can plan for either a single-story building consuming the entire allowable area in one floor, or a multi-story building that rises higher above the plane of the land, but which must consequently result in a smaller footprint than would a single-story building of the same total floor area. By combining the horizontal and vertical limits into a single figure, some flexibility is permitted in building design, while achieving a hard limit on at least one measure of overall size. One advantage to fixing this parameter, as opposed to others such as height, width, or length, is that floor area correlates well with other considerations relevant to zoning regulation, such as total parking that would be required for an office building, total number of units that might be available for residential use, total load on municipal services, etc. The amounts of these things tend to be constant for a given total floor area, regardless of how that area is distributed horizontally and vertically. Thus, many jurisdictions have found it unnecessary to include hard height limitations when using floor area ratio calculations.

Terminology

Similar terms

floor space ratio (FSR), floor space index (FSI), site ratio and plot ratio

Floor Space Index (FSI) Vs Floor Area Ratio (FAR)

While in terms of the outcome both will give the same built-up area that is allowed to be built on a certain area of land, there is an important difference in the representation of FSI & FAR. One is ratio and the other is index.

An index number is an economic data figure reflecting price or quantity compared with a standard or base value. The base usually equals 100 and the index number is usually expressed as 100 times the ratio to the base value. For example, if a commodity costs twice as much in 1970 as it did in 1960, its index number would be 200 relative to 1960. Index numbers are values expressed as a percentage of a single base figure. For example, if annual production of a particular chemical rose by 35%, output in the second year was 135% of that in the first year. In index terms, output in the two years was 100 and 135 respectively.

FSI Vs FAR, Example: Being able to build 1.5 times or 150% of land area will give us same result. But the difference is in denotation. When we say ‘FAR’ we have to say 1.5, However, when we want to say ‘FSI’ we have to say 150 or 150%.

Regional variation

The terms most commonly used for this measurement vary from one next.

In floor space ratio (FSR) is used in New South Wales^[1] and plot ratio in Western Australia.^[2]

In India floor space index (FSI) and floor area ratio (FAR) are both used.^[3][4]

In the United Kingdom and Hong Kong both plot ratio and site ratio are used.^[5][6]

In Singapore the terms plot ratio add gross plot ratio (GPR) are more commonly used.

In the United States and Canada, floor space ratio (FSR) and floor area ratio (FAR) are both used.^[7]

Use ratios are used as a measure of the density of the site being developed. The ratio is generated by dividing the building area by the parcel area, using the same units.

Impact on land value

Edward Ptacek (2009) noted that the allowable FAR has a major impact on the value of the land. Higher allowable FAR yields higher land value.

Criticism

Andres Duany (2000) notes:

1. Abdicating to floor area ratios (market forces) is the opposite of aiming a community toward something more than the sum of its parts.
2. FAR, a poor predictor of physical form, should not be used when the objective is to conserve and enhance neighborhood character; whereas traditional design standards (height, lot coverage and setbacks or build-to lines) enable anyone to make reasonably accurate predictions, recognize violations, and feel secure in their investment decisions.
3. If FAR is carelessly combined with traditional setbacks, assembled lots have a considerable advantage over individual lots, which has a negative effect on fine-grained cities and the diversity of ownership.

Japan

Japan has extensively adopted the floor area ratio in the zoning system since 1970. The evaluation of the adoption is, however, controversial: some say that it has deteriorated the skylines and building lines in Japanese cities;^[8] others claim that it has protected the residential environments.

Footnotes

References

• Meriam, Dwight (2004). The Complete Guide to Zoning. McGraw-Hill. ISBN 0-07-144379-7
• Birch, Eugenie L. (2009). "The Urban and Regional Planning Reader". Routledge. ISBN 0-415-31997-8

External links

• Blog post explaining floor area ratio and Space Index
• An explanation of the floor area ratio by J.H. Crawford