Where plumbing fixtures are provided, a portion must be accessible. IBC 1109 and A117.1 (603–610) set the requirements for toilet and bathing rooms: clear floor and turning space, water closet clearances and grab-bar geometry, lavatory knee and toe clearance and reach ranges, and accessible drinking fountains (including the high-low pairing). Single-user toilet rooms have their own layout rules.
The common mistake is an accessible stall that meets the area requirement but not the grab-bar placement or the required clearances around the fixture — or a lavatory positioned so it blocks the clear floor space.
Reviewers check the clearances, grab-bar locations, fixture reach, and that the required number of accessible fixtures is actually provided. It's often the geometry, not the count, that fails.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.