Ceiling heights: 7 ft rooms, 6′8″ baths, 5 ft on slopes

Under a slope, floor below 5 ft doesn't count.

The IRC ceiling numbers to check before you draw that attic bedroom: habitable rooms and hallways need 7 ft (2134 mm). Bathrooms, toilet rooms and laundry rooms can drop to 6′8″ (2032 mm). Under a slope, at least half of the required floor area needs 7 ft, and floor with less than 5 ft of height doesn't count toward the required area. Basement areas without habitable space need 6′8″, with beams and ducts allowed down to 6′4″. These are model code minimums, so always check the edition your city has adopted.