We just learned that there are tax exclusions in Alameda County, CA for conversion of existing space for disabled access as well as for adding fire sprinklers.
While almost all of our readers are outside of Alameda County, this is a question we should be sure to ask early in the design process. It will be a tough one to get an answer to.
This seems to reside at the intersection of the planning department and the assessor’s office – two bureaucracies that have almost nothing to do with each other. If this is done properly it can mean a big deduction. If it is not, it can mean you miss out entirely.
For example, I believe that a conversion of “existing space” is not assessable. So it may make sense to do a minimal existing space addition as bare bones as possible. For example, make one big habitable “great room” or even a garage or office, have that assessed, then spend the expensive dollars on a bathroom, kitchen, flooring, egress windows, ramps, low threshold transitions etc… in order to make something accessible.