Does a bay window count as square footage?
Published August 27, 2026
Yes, if it has a floor. Because ANSI Z765 measures to the exterior walls, a bay window that extends the room's floor to the outside wall of the bay, with a ceiling of at least 7 feet, is included in gross living area. A box bay or window seat that projects from the wall above floor level, with no floor beneath it at room level, is not.
How appraisers handle it
The bay is measured as a small bump in the exterior footprint. On a sketch it adds a few square feet, which is why bay windows show up as odd angles on appraisal drawings. That is a direct result of ANSI measuring from the outside of the walls.
Bay window vs. bow window vs. box bay
- Bay window: three panels angled out from the wall, usually with a floor extension. Counts if the floor is at room level.
- Bow window: a curved run of four or more panels; same test, floor decides.
- Box bay or garden window: a shelf-like box above floor height. Does not count.
A window seat built into a bay with floor beneath it counts; the seat is just furniture on countable floor.