What spaces are explicitly excluded from the Carpet Area?

Sanitary accommodations, verandahs, balconies, and corridors or passages are excluded from the carpet area.

Are internal partition walls included in the Carpet Area?

No, IS 3861 explicitly excludes both external and internal wall thicknesses from the carpet area measurement.

How is a shared staircase treated when measuring Rentable Area?

Common areas like shared staircases are typically apportioned pro-rata to the rentable areas of the respective units sharing them on that floor.

Are machine rooms or AC ducts included in Rentable Area?

No, areas of machine rooms, air-conditioning ducts, and similar service utility spaces are excluded from rentable area.

IS 3861

: 2002

Method of Measurement of Plinth, Carpet and Rentable Area of Buildings

CurrentFrequently UsedMethod of MeasurementBIMArchitectural · Methods of Measurement of Works of Civil Engg.

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This standard provides a uniform method for measuring the plinth area, carpet area, and rentable area of buildings. It establishes clear inclusion and exclusion criteria for spaces such as balconies, staircases, lifts, and ducts to ensure standard calculation practices in architecture, real estate, and valuation.

Method of Measurement of Plinth, Carpet and Rentable Area of Buildings

Quick Reference Values

linear measurement accuracynearest to 0.01 m

area measurement accuracynearest to 0.01 sqm

internal walls in carpet areaexcluded (0%)

external walls in carpet areaexcluded (0%)

balcony in carpet areaexcluded (0%)

Practical Notes

Engineers and architects must distinguish between IS 3861 Carpet Area (which excludes internal partition walls) and the RERA Carpet Area (which includes internal partition walls).

Plinth area must include the external wall thickness and is measured at the floor level of any given storey.

Open-to-sky courtyards, cantilevers, and un-enclosed porches are generally excluded from plinth area measurements.