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. Bump-outs like this are grouped in what counts as square footage.
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. A cantilevered floor and an interior chimney follow the same exterior logic.
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.