Accessory Home 101

How to get started.

There are generally four steps to building an Accessory Home: image of construction

  • Kickoff - Determine if your property is a good candidate for an Accessory Home, check your well and septic capacity, and set your budget or secure financing options.
  • Design - Once you secure an architect/contractor you will start to design your Accessory Home. You can also select from free plans provided by Placer County.
  • Permits - You will be issued permits to start construction. The number and types of permits needed for an Accessory Home may vary. Public utility permits/use fees are waived for qualified Accessory Homes.
  • Construction - When you have your building permits, you can start the construction of your Accessory Home. The builder you hire will lead this step.  

What you need to know.

  1. Size
  2. Parking
  3. Building Permits
  4. Utility Connections
  • An Accessory Home is intended to be secondary in size to the primary home. 
  • An Accessory Home that is attached to a primary dwelling may be up to 50% of the existing unit. 
  • An Accessory Home that is detached from the primary home may be up to 1,200 square feet, regardless of the size of the primary structure.      
  • There is no minimum lot size for an ADU, but adequate water and sewer or septic must be demonstrated.

NEW! Fee reductions for ADUs

No impact fees will be assessed for units less than 750 square feet. For a unit that is 750 square feet or more, the impact fees are proportional to the primary unit.

Size of Unit (square feet)Percent of Development Impact Fees Assessed 
749 square feet and below0%
750 - 1,00050%
1,001 and above 100%

The type of permits required to build an ADU can vary. See here for more Building Permit information or to begin your online application process.

Calculate Cost.

Use our calculator tool to determine your permit and construction cost based on where you live in Placer County.

View Free Plans.

Save money by choosing one of these free plans.

Get Inspired.

See what your neighbors are building.


If you are interested in building an Accessory Home, fill out this form and email it to Meghan Schwartz at [email protected]. You can schedule an appointment by calling Meghan Schwartz at (530) 745-3075 or by e-mail at [email protected].