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- Accessory Home 101
- Accessory Dwelling Unit (ADU) FAQs
Accessory Dwelling unit (ADU) FAQs
- Where are Accessory Homes allowed?
At this point in time every parcel zoned residential in Placer County is allowed to have up to three dwellings. One primary dwelling, one ADU and one JADU. The ADU can be up to 1,200 square feet if detatched from the primary unit, or up to 50% of the primary dwelling square footage if it is attached. The JADU can be up to 500 square feet and needs to be built within the framework of either the primary or ADU.
- Is a permit required for a new Accessory Home?
Yes, in all cases a building permit is required. Property owners interested in constructing an Accessory Home on their property are encouraged to speak with our Accessory Home team prior to preparing construction documents, to discuss your concept and verify what permits will be needed. Please e-mail firstname.lastname@example.org.
- Can an Accessory Home be sold separately from the primary residence?
No, accessory homes cannot be sold separately from the primary dwelling unit.
- Can an Accessory Home be rented?
Yes, however, rental of the Accessory Home for thirty (30) days or less is prohibited.
- What is the maximum size an Accessory Home can be?
An attached Accessory Home may be up to fifty percent of the existing living area of the primary residence. A detached Accessory Home is limited to a maximum total floor area of 1,200 square feet.
- Can I add a “tiny home” as an Accessory Home?
Yes, tiny homes are permitted in Placer County.
- How many accessory homes can I build on my property?
At this point in time every parcel zoned residential in Placer County is allowed to have up to three dwellings. One primary dwelling, one accessory home (ADU) and one Junior ADU (JADU).
- What is a Junior Accessory Home?
A Junior Accessory Home is a living unit of 500 square feet or less contained completely in a single-family dwelling or an accessory dwelling.
- What is the difference between an Accessory Home and a Junior Accessory Home?
An Accessory Home can be attached or detached from the primary dwelling. A Junior Accessory Home needs to be built within the framework of the primary dwelling or Accessory Home.
- Where are Junior Accessory Homes allowed?
A Junior Accessory Home is permitted in single and multiple family residential zones.
- Is a permit required for a new Junior Accessory Home?
Yes, in all cases a building permit is required. Property owners interested in constructing a Junior Accessory Home on their property are encouraged to speak with our Accessory Home team prior to preparing construction documents, to discuss your concept and verify what permits will be needed.
- Can a Junior Accessory Home be sold separately from the primary residence?
No, Junior Accessory Homes cannot be sold separately.
- What is the maximum size a Junior Accessory Home can be?
The maximum square footage of a Junior Accessory Home is 500 square feet.
- Is parking required for a Junior Accessory Home?
- Do JADUs require a deed restriction?
Yes, an owner-occupancy deed restriction is required for JADUs unless owned by a government agency or nonprofit.
- What are the impact fees for ADUs?
Impact fees are waived or reduced when building an ADU.
- All impact fees are waived on ADUs less than 500 sf.
- All impact fees are waived, except school fees on ADUs less than 750 sf.
- For ADUs larger than 750 sf impact fees are proportional to the size of the primary dwelling. Ex: a 1,200 sf ADU with a primary dwelling of 2,400 sf will pay 50% of the impact fees.
- How much money can I save by using Placer County’s preapproved plans?
Using Placer County’s pre-approved plans will save an estimated $6000-$10,000 in design fees. In addition, the review period will be reduced because the plans are preapproved.
- Is there any financial assistance in building/permitting my ADU?
Yes! Currently, CalHFA is offering a $40,000 grant to help with building an ADU. Check out our Financing and Grant Assistance page to see these opportunities.
- Can a portion of an existing house, garage or other accessory structure be converted to an Accessory Home?
Yes, provided the structure was legally constructed with building permits and the structure can be upgraded to meet the current building code requirements for a living unit. When an existing garage or other accessory structure is converted to an Accessory Home, no additional building setback verification is required. The Accessory Home must have independent exterior access from the existing residence.
- Can an Accessory Home be constructed above or attached to a garage?
Yes, provided the garage was legally constructed with building permits, the structure can be upgraded to meet the building code requirements for a second story and a living unit. An Accessory Home constructed above a garage must meet the setbacks required by zoning.
- How close can an ADU be to a property line or adjacent building?
Fire separation will need to comply with tables R302.1(1) and R302.1(2) of the California Residential Code. ADUs equipped with automatic sprinklers require a 1-hour rated exterior wall if constructed within 3’ of a property line or 6’ from an adjacent sprinklered structure on the same lot. ADUs not equipped with fire sprinklers require a 1-hour rated exterior wall if constructed within 5’ of a property line or 10’ of an adjacent building on the same lot. For ADUs that are attached to a primary dwelling, 1-hour rated wall and/or floor assemblies are required to separate the dwelling units. See CRC R302 for additional information. Fire separation requirements do not apply to JADUs that are built within the walls of an existing dwelling.
- Are automatic sprinklers required in my ADU?
Per R313.2, ADUs are exempt from automatic fire sprinkler system requirements if ALL the following are met:
- The unit meets the definition of an Accessory Dwelling Unit as defined in the Government Code Section 65852.2.
- The existing primary residence does not have automatic fire sprinklers.
- The ADU does not exceed 1,200 square feet in size.
- The unit is on the same lot as the primary residence.
- Can I convert my existing garage to an ADU?
Yes, existing accessory structures can be converted to an ADU. Some important considerations to keep in mind are:
- Fire separation requirements per R302.
- Structural adequacy of existing structure. If existing structural members are subjected to increased loads, structural retrofit may be required. (Example: The ceiling joists for an existing garage may have been sized without considering the additional weight of drywall, mechanical units, etc.)
- A vapor retarder is required per R506.2.3. If one was not installed during construction of an existing slab, a post installed product may be used. If installing a post installed vapor barrier, Placer County requires that an alternate materials request form be submitted along with product specifications. Requests will be reviewed on a case by-case basis. Placer County is currently working on providing a list of pre-approved products that can be used as a post installed vapor barrier.
- What kind of egress requirements apply to my ADU?
ADU egress will need to comply with R311. Below is a list of some (but not all) applicable code requirements:
- Not less than one egress door. Door shall be side hinged and shall provide not less than 32” clear opening (sliding glass doors do not meet this requirement). The required egress door shall open directly into a public way or to a yard or court that opens to a public way. Egress shall not require travel through a garage.
- JADUs require a separate exterior access from within the unit. The required access shall meet egress requirements.
- Can a single HVAC system be installed to serve both the primary dwelling and attached ADU?
No. CMC 311.4 prohibits the transfer of air between adjacent dwelling units. Separate HVAC systems are required for each dwelling unit.
- Does my ADU require separate utility meters?
ADUs are eligible for, but do not require individual utility meters. If you are planning on extending utility connections from the primary dwelling to the ADU, you will need to demonstrate that the existing utilities are adequate to serve the proposed ADU. (Example: gas line sizing diagram, electrical load calculations, drainage fixture unit calculations, etc).
- Does my ADU require solar?
For new construction, the CA Energy Code 150.1 typically requires a new PV solar system to be installed to meet the prescriptive or performance energy design for the ADU. There are some exceptions, such as (but not limited to) participation in a shared solar electric generation system (CEC 150.1(b)(1), exception), and limited solar access (CEC 150.1(C)14, exception 1). Solar is not required for attached ADUs or conversions of existing space, including existing permitted attached and detached garages.
- Does my project need to comply with Wildland Urban Interface requirements?
If your project is located within any Fire Hazard Severity Zone or Wildland Urban Interface Fire Area, then it will need to comply with the materials and construction methods outlined in CA Residential Code R337, as amended by Placer County. The requirements of R337 apply to new construction and to significant additions/remodels where the roofing, siding, and windows are all replaced within (1) year of building permit issuance per Placer County Code 15.04.270.
- Is parking required for an Accessory Home?
An Accessory Home must provide one parking space. The parking space may be covered or uncovered and can be provided on an existing driveway. If the required parking for primary residence is displaced by Accessory Home and one additional parking space is provided for the Accessory Home, then the replacement parking spaces for the primary residence may be covered, uncovered, tandem, or spaces created by mechanical automobile parking lifts.
- Can parking for an Accessory Home be waived?
Parking for an Accessory Home may be waived in any of the following instances:
- The Accessory Home is located within one-half mile of public transit, including transit stations and bus stations.
- The Accessory Home is located within an architecturally and historically significant historic district.
- The Accessory Home is part of the existing primary residence or an existing accessory structure.
- When on-street parking permits are required but not offered to the occupants of the ADU.
- When there is a car share vehicle located within one block of the ADU.
- What if my HOA does not allow an Accessory Home?
Homeowner associations (HOAs and CC&Rs) must allow the construction of Accessory Homes according to recent state legislation (AB 670).
- Can I build an accessory home in North Lake Tahoe?
Additional regulations apply for homeowners wishing to build an accessory home in the Tahoe Basin as determined by Tahoe Regional Planning Agency (TRPA). Determine if your residence is restricted within the TRPA coverage area by going to parcels.laketahoeinfo.org.
- What is the minimum lot size required for an accessory home?
There is no minimum lot size required for an accessory home in most of Placer County.
- Can an ADU have a covered porch?
Yes, a cover porch is allowed. It does not subtract from the maximum square footage of the ADU. The covered porch also gets the same reduced setbacks as the ADU, 4 feet side and rear.
- What is the maximum square footage of a covered porch?
The size of the covered patio cannot be more than 25% of the maximum living space.
- Do ADUs/JADUs need to have a kitchen?
Yes, ADUs/JADUs need to have a kitchen facility, by definition: any appliances for the preparation or preservation of food, including, but not limited to, gas or electric ranges, ovens or stovetops, refrigerators or freezers of more than five cubic feet capacity, and cabinets designed to accommodate such appliances. Microwaves alone would not constitute "cooking facilities." That is more aligned with a guest house or wet bar.
- What about a combined ADU/JADU?
When attaching a JADU to an ADU the total square footage of both dwellings combined, cannot exceed 1,200 sf.
- Can I connect my ADU/JADU to my existing septic system?
To determine the septic requirements for an ADU/JADU Environmental Health staff will need to review the file for your parcel. Based upon the age of the system, sizing of the system and other required data our staff will determine the sewage disposal requirements for the ADU. More than likely, soils testing (perc and mantle) will need to be completed with Environmental Health and a private sewage disposal consultant. ADUs must be sized for a minimum of 2 bedrooms and be served by a separate septic tank.
- If my existing home is on septic but public sewer is nearby what are my requirements?
If public sewer is physically and legally available within 300 feet of any portion of the property boundary the ADU/JADU will be required to connect to public sewer. Additionally, all structures on the property with plumbing would also be required to connect to public sewer as well.
- If I use a tiny home as my ADU/JADU are the septic system requirements different?
The septic requirements are the same for all types of construction of the ADU (traditional construction, manufactured home, tiny home etc).
- If I convert the space above my garage to an ADU do I still need a new septic system?
An ADU must be served by a separate septic tank and the leachfield is required to be sized for a minimum of 2 bedrooms. If the existing septic system is not adequately sized and/or adequate data regarding the system does not exist, soils testing will be required to determine the sewage disposal requirements for the ADU.
- What is the 100% repair area and can I use this area for the construction of my ADU?
The 100% repair area is an area designated on your property where a new leachfield would be installed at the time of failure of the current septic system. An adequately sized 100% repair area is required for all structures on the property. This area must be free of structures, grading, parking, driveways etc. and must meet all required setbacks.
- What are the domestic water supply requirements for an ADU?
In order to construct an ADU/JADU the parcel must be served by a potable water supply defined as either public treated water or a domestic water well drilled under permit. A domestic water well must produce a minimum of 1 GPM per residential unit. A 4-hour well yield dated within the last 3 years may be required to provide evidence of water quantity. Ditch water, spring water and hand dug wells are not considered a potable water supply. Parcels would be required to obtain a potable water supply prior to Environmental Health approval of the building permit for the ADU/JADU.
- If the ADU is detached and built at same time as the primary unit?
Charge SFD connection fees and all fees for ADU’s at 0.714 EDUs.
- If the ADU is attached and built at same time as the primary unit?
No additional charges, no connection fees, no O&M fees. If the property is on a STEP system see STEP information below.
- If the ADU is detached and built later?
Lot cannot be split
- No connection fees, but still charged 0.714 EDUs for O&M and usual inspection fees.
- Additional O&M fees apply for STEP system maintenance if a STEP system is required on the parcel.
- If the ADU is detached on a splittable lot?
Lot can be split and ADU is situated on portion that can be a separate lot
- Standard Connection fees apply to the SFD and the ADU fees at 0.714 EDUs
- The ADU shall have its own connection point.
- If the applicant chooses to split the lot, the applicant is required to pay the remaining balance for full connection fees and the balance of O&M fees.
- Septic Tank Effluent Pump (STEP) Systems – Existing SFD and New ADU
Applicants proposing an ADU or JADU are required to upsize the existing STEP system to meet current standards at the applicants expense.
- Detached on a splittable lot, STEP systems – New or Existing SFD and New ADU
If there is sufficient room between the primary home and the ADU for a future parcel split, the applicant is required to install a second STEP system and connection point.
- Will I need an additional driveway?
It depends. For an additional driveway connecting to a County maintained road, an encroachment permit may be applied for. The Department of Public Works will review the application and determine whether an additional encroachment will be permitted.
- What about grading?
A grading permit may be required if the grading outside the footprint is extensive or if there are proposed retaining walls greater than 4ft in height or surcharged. For the complete list of work that requires a grading permit please see placer.ca.gov/2371/grading-permits.