What’s considered a single-family dwelling in California?

There seems to be a bit of confusion surrounding single-family dwellings, but CIRB, the most accurate source of California building permit statistics, is here to help.

There seems to be a bit of confusion surrounding single-family dwellings, and understandably so.

With permits for SDUs (Secondary Dwelling Units), ADUs (Additional Dwelling Units), tiny houses, granny flats, condos, townhomes, conversions, fire rebuilds, etc. being issued all across the state, a true single-family dwelling has become difficult to define—but CIRB is here to help.

CIRB has been tracking permits since 1954, and with the publication of the 2018 Annual Building Permit Summary report—detailed compilation and analysis of California permit activity (purchase here)—we now report building permit data at a 99.4% annual compliance rate.

Reaching this level of accuracy requires regular communication with the building departments of all 539 California jurisdictions to not only obtain records of permits issued, but to also work with staff on identifying and classifying permits for new homes.

Below are the criteria by which CIRB includes (or does not include) a new single-family dwelling (SFD) in its data reports:


  • Detached, semi-detached and attached one-family houses
  • Condos*, townhouses* or row houses
  • Prefabricated, sectionalized, panelized, and modular homes (manufactured partially offsite and assembled at the construction site)
  • Secondary or additional dwelling units, guest houses, granny flats and casitas
  • Fire rebuilds, if a complete rebuild or demo and rebuild is indicated

Not included

  • Conversions or remodels of an existing structure into an SFD
  • Mobile homes
  • Temporary or transient housing
  • Convalescent homes or memory care facilities
  • *Condos and *townhomes are considered multi-family (apartments) if they are 3 or more units and under the same continuous roof or are in a multi-story building and constructed above or below one another

So how does this shape permit totals in CIRB reports?
Due to the inclusion of rebuilds and ADU/SDUs, CIRB’s total housing units for California may be higher than other sources are reporting.

<<Click here to check out our historical units chart for current and past building trends.>>

However, CIRB data analysts go directly to the local building department to investigate and confirm the units reported in each monthly publication of building permit activity.

Our motto is every permit counts. And accuracy is our specialty.

Want to keep up with current housing activity in California? Click here to subscribe to the CIRB Report or CHF-CIRB@mychf.org for more information on building permit data, custom reports, and more.