Do laundry rooms, mechanical rooms, and under-stair storage count as square footage?
Published August 27, 2026
Yes, if finished and on a finished floor. A laundry room, mechanical closet, or under-stair storage space that is finished (walls, floor, ceiling) and sits on an above-grade finished level counts as gross living area under ANSI Z765. The same rooms in a basement are below-grade area, and an unfinished utility room (bare studs, slab) on any level does not count. Utility space sits with closets and halls in what counts as square footage.
The furnace room test
A furnace room does not have to be pretty, but it has to be finished to the house standard: drywalled, with a finished floor and ceiling. A concrete-floored mechanical room with exposed framing off a finished hallway is excluded from the finished area even though it is inside the exterior walls. Warmth from the furnace does not help, since heat alone is not the test, and a finished utility room counts the same way closets and hallways do.