Does a chimney count as square footage?
Published August 27, 2026
Inside the walls, yes; bumped out from the wall, no. ANSI Z765 measures the exterior of the house, so a fireplace and chimney that sit inside the exterior wall line are part of the footprint and are counted like a closet. An exterior chimney that projects outside the wall is not living area and is not measured into the square footage.
Fireplace bump-outs
A fireplace built into a small bump-out of the exterior wall is a judgment call: if the bump-out has floor and ceiling at room level (a real alcove), it is measured like a bay window; if it is just masonry, it is not. Either way it is a few square feet, which is why the standard treats it simply.