Accessory Home 101
How to get started
Considering building an Accessory Home on your property? Placer County is here to assist you with the process. There are generally four steps to building an Accessory Home:
- 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. Continue to read through this page to learn more.
- 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. Learn more
- 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. Learn more
- Construction - When you have your building permits, you can start the construction of your Accessory Home. The builder you hire will lead this step. Learn more
What you need to know
- 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 Accessory Home, but adequate water and sewer or septic must be demonstrated.
There is a state requirement for one parking space per Accessory Home or per bedroom, whichever is less. However, additional parking is not required for a proposed Accessory Home that is:
- Within one-half mile of a public transit stop
- Within an architecturally and historically significant historic district
- Within the existing single-family dwelling or an existing residential accessory structure
- In an area where on-street parking permits are required but not offered to the occupant of the secondary dwelling
- Within one block of a car share vehicle pick-up location
- A junior accessory home
- Converted from a garage, carport, or other covered parking space, or if a garage, carport, or other covered parking space is demolished in conjunction with the accessory or junior accessory dwelling unit construction
- Multiple permits are typically required to establish an ADU.
- Before applying for a building permit, property owners should investigate water and septic suitability to find out if there any additional requirements needed prior to proceeding with design plans.
- Once it has been determined that you are able to build an Accessory Home on your property whether it is converted space or new construction, you will need to obtain a building permit to ensure that the living area meets building and safety codes.
- You can apply for your permits here through our e-services portal.
- Accessory Homes are required to provide the necessary utility services such as water and sewer.
- Water availability and soil suitability for a septic system are significant factors that determine whether a permit for an Accessory Home can be issued.
- Property owners are advised to investigate water availability and septic suitability prior to proceeding with design plans.
- The construction of an accessory dwelling unit represents a new use on the property which must meet current codes with respect to the septic system for the unit. If one septic system is to serve both the main dwelling and accessory unit, the septic system must meet current code requirements and be adequately sized for the proposed sewage discharge (based upon total number of bedrooms in the two units).
- Check with each of your service agencies to obtain information on their requirements including permit processing and fees.
It is also important to consider how you will pay for the permitting and construction of your Accessory Home. There are a handful of financing options including:
- Cash savings/other liquid assets
- Cash-out refinance
- Loans from friends/family
- Home equity loan or home equity line of credit
- Renovation loans
The cost of building an Accessory Home varies. To get a sense of how much your home might cost, take a look at the County’s Accessory Home Calculator.
NEW fee reductions for Accessory Homes
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.
|Accessory Home Size||Primary Dwelling Size||Impact Fees|
499 square feet or less
|No impact fees|
500 to 749 square feet
|No impact fees*|
750 square feet
1,500 square feet
(750/1500)*100% = 50% impact fees
800 square feet
2,400 square feet
(800/2400)*100% = 33.33% impact fees
1,200 square feet
|2,400 square feet|
(1200/2400)*100% = 50% impact fees
|1,200 square feet||4,800 square feet|
(1200/4800)*100% = 25% impact fees
Impact fees are applied to Accessory Homes 750 square feet and greater up to 1,200 square feet. The square footage of the Accessory Home is compared to the square footage of the primary dwelling. To determine your impact fees take the square footage of your Accessory Home and divide that by the square footage of your primary dwelling then multiply by 100% and that will give you your percentage of impact fees.
*School fees still apply to Accessory Homes that are between 500 and 749 square feet. School fees vary in each school district and are administered based on the square footage of the intended residential building.