Do Stairs Count as Square Footage?

Short answer: stairs count as square footage on the floor where they begin, but the stairwell void above does not count on the upper floor. The net result is that a staircase contributes roughly the area of the stair footprint once — not twice.

The rule: count once, deduct the void

Under ANSI Z765 and standard appraisal practice, gross living area is measured from the exterior perimeter on each floor. For a two-story home:

First floor: The staircase footprint is included in the first-floor perimeter — the stairs sit on the first-floor slab or subfloor, so it is part of that level's square footage.
Second floor: The stairwell creates an open void (a hole in the second floor). That void is not part of the second floor's living area. It is excluded when calculating the second-floor GLA.

The staircase itself — the physical steps — is part of the structure connecting the floors. It occupies space on the first floor, creates a void on the second floor, and the two roughly cancel out in total GLA.

How to handle this in PlanSnapper

When tracing the second floor of a multi-story home in PlanSnapper, you have two options:

Trace the full second-floor perimeter and subtract the stairwell void: Draw the outer polygon for the full second floor, then draw a second polygon around the stairwell opening and note it as a deduction. Most appraisers use this approach — it is explicit and auditable.
Trace around the stairwell: Instead of tracing the full rectangular perimeter, add extra polygon points to route around the stairwell void, excluding it from the shape. This works well when the stairwell is at an exterior corner.

Either approach produces the correct GLA for the second floor. The first method is more transparent for appraisal documentation.

What about open-to-below areas?

A stairwell is a specific case of “open to below” — an area where the floor of the upper level has been removed to create height. The same rule applies to any open-to-below void: it is counted on the lower level (which still has a floor) and excluded on the upper level (where the floor is missing).

Common mistakes

Double-counting: Including the stair footprint on both the first and second floor. This overstates GLA by the stairwell area (typically 40 to 80 sq ft in residential homes).
Zero-counting: Excluding the staircase from both floors. This understates GLA by roughly the same amount.
Ignoring landings: Landings are finished floor space at an intermediate level. They count as GLA if they are above grade, finished, and heated — and the ceiling height at the landing meets the ANSI Z765 minimum of 5 feet.

Does stair square footage matter much?

In most homes, a stairwell is 40 to 80 square feet. At $100 per square foot GLA adjustment (a typical mid-market rate), that is a $4,000 to $8,000 difference in appraised value if counted wrong. It is not a trivial error when the staircase runs multiple flights or when the home is in a high-cost market.

Measure each floor accurately

Upload a floor plan for each level and trace each floor separately. PlanSnapper totals the above-grade GLA automatically.

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