CBC 1.8.2.1 General. See the CalIfornia Residential Code for detached one- and two-family dwellings and townhouses.
CBC [A] 101.2 Scope.Detached one- and two-family dwellings and multiple single-family dwellings (townhouses) not more than three stories above grade plane in height with a separate means of egress and their accessory structures shall comply with the California Residential Code.
The FEDERAL Fair Housing Act's design and construction requirements do not cover multistory townhouses--units that have two, three, or even four stories--unless the building has an elevator. There is a discussion of townhouses in the preamble to the Guidelines under "Section 2-Definitions [Covered Multifamily Dwellings]" at 56 FR 9472, 9481, March 6, 1991.