Do Stairs Count as Square Footage?
Yes, stairs count as square footage. Under the ANSI Z765 standard appraisers use, the treads and landings count with the floor the stairs descend from, and the floor space under them counts with the level below, so a staircase shows up on both floors.
Which floor do stairs count on?
Stairs count on the floor they start down from, and the space under them counts on the floor below.
Stairs count with the floor from which they descend
That's the wording in Fannie Mae's summary of the ANSI standard. Realtor training on ANSI adds that space under stairs counts with the floor below, with no minimum ceiling height there.
It isn't double counting by mistake. Each floor is measured to its own outside walls, and the staircase sits inside both outlines. The total of those finished, above-grade floors is the home's gross living area, and the rest of the rules are in the ANSI Z765 standard.
Why listings disagree: the American Measurement Standard (AMS) leaves stairwells out of living area, while ANSI includes them. A listing and an appraisal can differ by the stairs alone.
Do you subtract the stairwell opening?
Subtract only the part of the opening that's open to the floor below, never the stairs themselves. If the hole in the floor is the same size as the staircase, there's nothing to subtract.
- Measure the upper floor to its outside walls: 1,000 square feet.
- Measure the opening: 12 × 7 = 84 square feet.
- Measure the stairs: 3 × 12 = 36 square feet.
- Subtract the open part only: 84 minus 36 is 48, so the upper floor is 952 square feet.
- Don't subtract anything downstairs. The lower floor keeps its full 1,000, so the home is 1,952 square feet.
Enter each floor as its own area in the house calculator to total them, and how to calculate square footage covers measuring each one.
Landings, split-levels and basement stairs
The same rule covers every case: find where the flight starts going down.
Count with the floor above, like the treads, including a wide switchback landing.
Each short flight counts with the level it descends from, so no level needs to be the "main" one.
They descend from the main floor, so they count there. The space under them stays basement area.
Basements and other below-grade space are reported apart from living area; what counts as square footage covers the rest of the house.
Frequently asked questions
Do stairs count as square footage twice?
Effectively, yes. The stairs count on the floor they descend from, and the floor under them counts on the level below, because each level is measured to its own outside walls.
Do you include stairs in the square footage of a house?
Yes. ANSI Z765, which Fannie Mae has required on appraisals with effective dates from April 1, 2022, includes stairwells in finished area. Only the open space beside the stairs is left out.
Does the space under the stairs count?
Yes, on the lower floor, and there's no minimum ceiling height for it. A low closet under the stairs is still part of that floor.
Do stairs to an unfinished basement count?
The flight counts with the finished floor it descends from. The area under it is part of the basement, which is reported separately from above-grade living area.
How do you calculate the square footage of stairs?
Multiply the staircase width by its length in plan view, not along the slope. A flight 3 feet wide and 12 feet long covers 36 square feet.