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.
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.