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Affordable Housing Program for Residential Development

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The purpose of the Affordable Housing Program for Residential Development is to implement Housing Element policies and programs (policies HE-3k and HE-3p and Program #22) by requiring that all residential development contribute to the County’s affordable housing program through one of a variety of options: 

  1. Constructing a percentage of the units as affordable,
  2. Paying an in-lieu fee, or
  3. Providing an equivalent alternative, such as land dedication or restricting existing units. 


The Program applies to all residential development, including construction of a single-family home on an individual lot. Individual home builders may either pay an in-lieu fee or may provide affordable housing by constructing an accessory dwelling unit, farm family unit, agricultural employee, or farm worker housing unit. Multifamily developments may pay an in-lieu fee or set aside a portion of the units constructed as affordable. 

Permit Requirements

An applicant must select the method of participation in the Program and submit the selected option with the first application for permits or approvals for the project. 

Standards for Construction of Affordable Units On-Site

At least 20 percent of the units in an ownership development must be affordable, half of which must be for low-income households (as defined in the Sonoma County Code) and half for moderate-income households (as defined in the Sonoma County Code). 

At least 15 percent of the units in a rental project must be affordable to low- and very low-income residents, or 10 percent of the units must be affordable to very low- and extremely low-income households. 

In-Lieu Fee

An in-lieu fee may be paid in place of construction of affordable units on-site. Fees are graduated based on unit or home size, with a smaller fee charged for smaller units or homes and a corresponding higher fee for larger units or homes. The in-lieu fee is adjusted annually to keep pace with inflation. 

The fee is paid prior to building permit final.

Affordable Housing Residential Fees


  • Accessory dwelling units and junior accessory dwelling units are exempt from these requirements. Residential remodels and replacements, including additions of up to 1,000 square feet, are also exempt.
  • Farm family units of up to 1,200 square feet, agricultural employee units of up to 1,200 square feet, and seasonal, year-round, and extended seasonal farmworker housing are exempt.
  • Dwelling unit destroyed by fire or natural catastrophe provided that a building permit for repair, reconstruction, or replacement has been issued and construction begun within 10 years of destruction.
  • Residential replacement units are exempt if the size of the new home is not more than 1,000 square feet larger than the home being replaced.
  • Residential accessory structures with 1,000 square feet or less of habitable space are exempt.