Does a floor plan need to follow ANSI Z765?

What ANSI Z765 is

ANSI Z765, "Square Footage: Method for Calculating", is a voluntary national standard for calculating and reporting the above-grade and below-grade square footage of single-family detached and attached homes. It does not apply to apartment or multifamily buildings, and it does not cover room dimensions.^[2] The 2021 version is the one in use; its next review is due no later than 2028.^[3]

In other words, ANSI Z765 is about one number, the home's square footage, and how to arrive at it. It is not a standard for floor plans in general, and it does not certify any tool, tape, laser or app.

When a floor plan has to follow it

• Fannie Mae appraisals with an inspection. Appraisers must follow ANSI Z765-2021 for the above- and below-grade square footage of single-family homes, including townhomes and manufactured homes, in all hybrid appraisals and appraisals with interior and exterior inspections.^[1]
• Not for desktop appraisals. Fannie Mae does not require ANSI for desktop appraisals but encourages it when feasible.^[4]
• Not for condos and apartments. ANSI cannot be used for apartment or multifamily buildings; for a condo unit the appraiser uses interior perimeter measurements.^[1]
• State law first. If state law or regulation requires a different standard, the appraiser notes it and explains how it was applied.^[1]

What the standard asks for

Fannie Mae Standardizing Property Measuring Guidelines (September 2025); exterior measurement explained by an appraiser writing for NAR.^[5][6]

Rule	What it means in practice
Measure from the outside	Each above-grade floor is measured from the exterior walls
Precision	Measure to the nearest inch or tenth of a foot; the floor plan shows dimensions to the nearest tenth of a foot; the total is reported to the nearest whole square foot
Ceiling height	Finished area needs a ceiling of at least 7 feet; in a sloped room at least half the area must reach 7 feet, and nothing under 5 feet counts
Below grade	Any level partly or fully below grade is reported separately as below-grade area
Stairs and open areas	Stairs count on the floor they descend from; openings to the floor below, such as two-story foyers, do not count

Where an interior scan fits

A room scan measures rooms from the inside. ANSI measures the house from the outside. The difference is the thickness of the exterior walls, and wall thickness is exactly what RoomPlan-based scans are weakest at: they often fall back to a default thickness.^[7] So an interior scan alone is not an ANSI square footage.

What a scan does give an appraiser or a sketcher is the hard part of the floor plan, quickly: every room, the interior walls, doorways and room labels, with the layout matched to a laser scan in a 2026 study.^[7] Fannie Mae accepts sketching and 3D scanning software, as long as the result conforms to ANSI.^[1] The exterior dimensions, the ceiling-height rules and the below-grade split are the appraiser's work on top.

PlaceAnew's plan shows room-by-room interior areas and a total. Treat them as room areas, not as an ANSI square footage.

Floor plans that do not need ANSI

• Design and remodeling plans, kitchen layouts and existing-conditions drawings for architects and contractors.
• Estimates for flooring, paint and finishes, which run on room and wall areas anyway.
• Marketing floor plans, with one caution: if a listing states square footage, say how it was measured, because an appraisal can arrive at a different number.^[6]

Questions people ask

Is ANSI Z765 the law?

No. It is a voluntary standard. Fannie Mae requires it for appraisals on the loans it buys, and a state can require a different method.

Can an app be ANSI certified?

ANSI Z765 is a method for measuring and calculating, not a certification for tools. What matters is whether the reported square footage follows the method, and that is the appraiser's responsibility.

Does ANSI Z765 apply to condos?

No. For an apartment or condo unit in a multifamily building, Fannie Mae uses interior perimeter measurements instead.

Where can I get the standard?

Start with Home Innovation Research Labs, the standard's secretariat. Its ANSI Z765 page names the version currently in use.

Next step

If you are an appraiser, read Can appraisers use a 3D scan for a floor plan? If you own or sell the house, read Can I use a phone scan for appraisal square footage?