SeeVirtual’s Standard For Calculating Residential Square Footage


Every once in a while, Realtors wonder and ask us how our total square footage is calculated. Depending on the types of properties we are measuring, we have different standards to follow to calculate the total usable square footage.

When measuring on-site, we take in as much information as we need to construct a complete floor plan on our tablet PC, often with extra measurements throughout the property to ensure we have collected data that are coherent. The information include wall thicknesses, room dimensions, windows, doors and appliances quantities and locations, staircases, garages and built-up outdoor spaces (such as decks and patios).

SeeVirtual’s Floor Plan square footage calculation practice for detached residential properties follows ANSI Z765-2003: Square Footage – Method for Calculating, as well as the American Measurement Standard for supplementary guidance. For condos and townhouses, we follow Section 68 of the BC Strata Property Act. We also use Builder Bulletin 22: Floor Area Calculations from ONHWP (Ontario New Home Warranty Program) as a standard for some items such as tolerance level for discrepancies where other standards do not cover.

All the Standards for detached homes are followed on a voluntary basis, whereas the Strata Act of BC is an official act that are to be followed when calculating square footage for strata units. Because of the lack of a unified standard for detached homes, there may be some discrepancies between our square footage and the builder’s plans when different methods are used, or that the final as-built homes deviated from the original plans.

The main difference for total square footage of detached house and strata properties is the perimeter wall of the property. For all detached houses, the total square footage includes the full thickness of the exterior walls, whereas the Strata Act of BC states that the strata units only includes half of the perimeter wall thickness and demising (sharing) walls.

When calculating the total square footage, we calculate the area enclosed by the outer perimeter of the floor plan and excludes any areas that cannot be counted as usable area. These excluded areas vary slightly with each standard, but as mentioned above, we follow ANSI Z765-2003 as the primary standard. Some examples of such areas are explained further below:

Sloped Ceilings

Ceiling height that is less than 5 ft cannot be counted in the total usable area. When there is sloped ceiling, at least one-half of the finished square footage in that room must have a minimum vertical ceiling height of 7 ft.

Left: sloped ceiling section; Right: sloped ceiling drawn on floor plan.

Unfinished Area within Finished Areas

If the utility room is a small unfinished space within and accessible from the finished area, then the American Measurement Standard allows this area to be included within total usable area to avoid excessive details.

Utility room with exposed wall framing under the stairs.

Separate Finished areas

If a property has a separate living area (basement suite, separate suite, studios, carriage house, etc) that is not directly accessible from the main living area (ie, the separate area is accessed through unfinished area, or from exterior), we must list the area separately.

Left: a finished area that must access through an unfinished area; Right: separate finished area.

Areas without Floors (Protrusions)

Chimneys, bay windows and other finished areas that protrude beyond the exterior finished surface of the outside walls that do not have a floor on the same level cannot be included in the calculation of square footage. However, if the window seat has storage below or is resting on a pony wall or extending to the same level as the floor, it can be included in the Total Usable Area.

Left: window seat without floor space; Middle: window seat with a floor visible below; Right: window seat with a storage space below that can be used as floor space once it’s removed.

Exterior Spaces and Seasonal Spaces

Outdoor spaces such as porches, patios, decks, balconies, and enclosed spaces such as sun rooms that are not finished or heated for year-round use are excluded from the total usable area.

Left: sunroom; Right: outdoor deck.

Whether you are having a measuring technician to measure and calculate the total usable area or you are doing it yourself, be sure to consider the above requirements and follow the proper standard guideline for the type of  property, then compare with the legal strata plan to see if there is any discrepancy. If you’re not confident with the calculation, have a professionally trained measuring technician to do the right job for you, then you can sit back and relax waiting for the magic number!

About Stanley - Floor Plan Technician

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