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. Fireplaces are one of the small shapes covered in what counts as 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, because unlike a cantilevered floor there is no floor to count. Either way it is a few square feet, which is why the standard treats it simply.