What is multifamily zoning and when do multifamily ADU rules apply?

Multifamily zoning allows for two or more attached dwellings on a single lot. Detached single-unit dwellings on one lot are not considered multifamily dwellings for the purposes of state ADU law. In other words, a lot with a permitted duplex would be considered a multifamily lot for ADU purposes, regardless of the underlying zoning, so long as it was zoned residential. A lot with an existing ADU, whether permitted or not, is not considered multifamily, unless the underlying zoning designates it as such.

• If you have a single house on a lot zoned for multifamily residences, multifamily ADU rules apply.
• If you have a condo on your lot, multifamily ADU rules apply.
• If you have an apartment complex on your lot, multifamily ADU rules apply.
• If you have a guest house on your lot and it's zoned single family residential, ADU rules DO NOT apply.

You can determine if multifamily zoning rules apply by checking your zoning code by requesting a Property Report with Housable or contacting your local planning office.