The American’s with Disabilities Act (ADA) requires an accessible path of travel in new construction and additions. When we’re talking about remodels, there is a cost threshold below which you are required to put in an accessible path.
First, you have to be making an alteration to a “primary function area”. A “primary function area” is any area where a major activity takes place whether that area is public or private including workrooms and offices in a commercial occupancy.
Second, the alteration is only required where it is not “disproportionate” to the cost of the alterations to the primary function areas. The ADA website puts this threshold at 20% of the cost of the alterations. If it will cost more than 20%, you’re not required to make the path fully accessible.
Oftentimes making a path accessible can be a minor expense, however where it will require significant ramps, elevators, revised stairs or changes to corridors you may discover that you fall above the threshold.
Finally, the ADA Standards for Accessible Design do not call this out but it is on their website.