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CALCULATION OF SQUARE FOOTAGE ANSI Standards

Noted from -
SQUARE FOOTAGE–METHOD FOR CALCULATING: ANSI Z765-2003

To claim adherence to this standard, the following methods of measurement and calculation must be employed when quantifying square footage in single-family houses.

When using English measurement units, the house is measured to the nearest inch or tenth of a foot; the final square footage is reported to the nearest whole square foot.

When using Metric or Standard International (SI) measurement units, the house is measured to the nearest 0.01 meter; the final floor area is reported to the nearest 0.1 square meter.

Calculation Methods

Calculation of square footage made by using exterior dimensions but without an inspection of the interior spaces is allowed but must be stated as such when reporting the result of the calculation. Calculation of square footage for a proposed house made by using plans must be stated as such when reporting the result of the calculation.

Circumstances can exist when direct measurement of a structure is not possible. Access to the interior may not be available and the nature of the terrain, structure, or other obstacles may preclude direct physical measurement of the exterior in the time available. Building dimensions developed through some means other than direct measurement or plans can be susceptible to inaccuracy, as is the calculated area. Calculation of square footage developed under such circumstances must be identified as such when reporting the result of the calculation.

Detached Single-Family Finished Square Footage

For detached single-family houses, the finished square footage of each level is the sum of finished areas on that level measured at floor level to the exterior finished surface of the outside walls.

Attached Single-Family Finished Square Footage

For attached single-family houses, the finished square footage of each level is the sum of the finished areas on that level measured at floor level to the exterior finished surface of the outside wall or from the center lines between houses, where appropriate.

Finished Areas Adjacent to Unfinished Areas

Where finished and unfinished areas are adjacent on the same level, the finished square footage is calculated by measuring to the exterior edge or unfinished surface of any interior partition between the areas.

Openings to the Floor Below

Openings to the floor below cannot be included in the square footage calculation. However, the area of both stair treads and landings proceeding to the floor below is included in the finished area of the floor from which the stairs descend, not to exceed the area of the opening in the floor.

The above-grade finished square footage of a house is the sum of finished areas on levels that are entirely above grade. The below-grade finished square footage of a house is the sum of finished areas on levels that are wholly or partly below grade. Ceiling Height Requirements

To be included in finished square footage calculations, finished areas must have a ceiling height of at least 7 feet (2.13 meters) except under beams, ducts, and other obstructions where the height may be 6 feet 4 inches (1.93 meters); under stairs where there is no specified height requirement; or where the ceiling is sloped. If a room’s ceiling is sloped, at least one-half of the finished square footage in that room must have a vertical ceiling height of at least 7 feet (2.13 meters); no portion of the finished area that has a height of less than 5 feet (1.52 meters) maybe included in finished square footage.

Finished Areas Connected to the House

Finished areas that are connected to the main body of the house by other finished areas such as hallways or stairways are included in the finished square footage of the floor that is at the same level. Finished areas that are not connected to the house in such a manner cannot be included in the finished square footage of any level.

Garages, Unfinished Areas, and Protrusions

Garages and unfinished areas cannot be included in the calculation of finished square footage. Chimneys, windows, and other finished areas that protrude beyond the exterior finished surface of the outside walls and do not have a floor on the same level cannot be included in the calculation of square footage.