Building Accessory Homes in Tahoe

What is an accessory home?

Granny flat, in-law suite, converted garage, backyard cottage, basement apartment – accessory homes, accessory dwelling units or ADUs go by many names, but are always a self-contained home smaller than the main house and legally part of the same property.

Accessory homes can take many forms and vary in size, but always contain everything someone needs to live, including a kitchen, bathroom, and place to sleep. Accessory homes typically range from 220 square-foot studios to nearly 1,200 square foot houses with multiple bedrooms. 

Did you know?

Now is a better time than ever to build an accessory home. Recent state legislation has significantly reduced or eliminated fees for many accessory homes. Homeowner associations (HOAs and CC&Rs) can no longer restrict the construction of accessory homes. Also to note, Placer County offers FREE plans, significantly saving you more money if you choose to use one.

When you build an ADU, you will save $20,000 in government fees plus $6,000 to $10,000 if you choose to use one of Placer's free building plans!

What you need to know to build in the basin!

Accessory Homes (ADUs) are allowed on parcels zoned for residential use in the Placer County portion of the Tahoe Basin under the circumstances outlined below. Download a printable file of the information below here.

Parcel Specifications

  • There is no minimum parcel size for an Accessory Dwelling Unit.
  • One ADU and one Junior ADU are allowed per parcel in addition to the primary dwelling.
  • All Tahoe Regional Planning Agency (TRPA ) coverage and development rights requirements apply and adequate water and sewer must be demonstrated. 

Size of Accessory Home

  • An ADU that is detached from the primary home may be up to 1,200 sq. ft. (does not include garage area), regardless of the size of the primary structure (per California Government Code Section 65852.2(a)(1)(D)(v). (TRPA coverage requirements apply)
  • An ADU that is attached to a primary dwelling may be up to 50% of the existing unit but shall be allowed to be up to 800 sq. ft. in size (per California Government Code Section 65852.2(a)(1)(D)(iv) and 65852.2(c)(2)(B)&C). (TRPA coverage requirements apply)
  • A JADU may be up to 500 sq. ft. (California Government Code Section 65852.22(h)(1).


  • TRPA evaluates coverage for ADUs just like any other addition to a single-family or multi-family project. See TRPA Code Section 30, Coverage, for more details on specific circumstances. To verify coverage on your parcel, visit the Parcel Tracker. If coverage has not been verified on your parcel you can apply for a Site Assessment or Land Coverage Verification here.
  • California law requires that ADUs be approved administratively, and local jurisdictions cannot restrict them based on allowable coverage or place income limits on the units.  For this reason, TRPA will perform the review of ADUs until such time as the state law or TRPA regulation is changed.

Occupancy and Ownership Restrictions

  • ADUs and JADUs in California cannot be short-term rented for 30 days or less. 
  • ADUs do not need to be deed-restricted to affordable, moderate, or achievable incomes, however in order to get a free bonus unit, a deed restriction is required consistent with TRPA Code Section 21.3.2.B.3.
  • All JADUs require that the owner occupy either the primary dwelling or the JADU, per Placer County Code 17.56.2.F.
  • A deed restriction on the JADU shall be recorded with Placer County that requires owner-occupancy of one of the units.


There is a state requirement for one parking space per ADU or per bedroom, whichever is less. However, additional parking is not required for a proposed ADU 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 residential accessory structure
  • Where on-street parking permits are required but not offered to ADU occupant(s)
  • Within one block of a car share vehicle pick-up location
  • A Junior Accessory Dwelling Unit
  • Converted from or due to demolition of a garage, carport, or covered parking space in conjunction with the ADU construction
  • In all other scenarios, parking requirements for ADUs shall not exceed one parking space per ADU. These spaces may be provided as tandem parking on a driveway. 
    • a) Offstreet parking shall be permitted in setback areas in locations determined by the local agency or through tandem parking, unless specific findings are made that parking in setback areas or tandem parking is not feasible based upon specific site or regional topographical or fire and life safety conditions. 
    • b) When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU, the local agency shall not require that those off-street parking spaces be replaced.

Residential Unit of Use 

An ADU shall be considered a residential unit subject to the residential allocation limitations and transfer provisions (TRPA Code of Ordinances Chapter 50). ADUs require a development right just as any other residential unit. ADUs can be built either with a bonus unit or with a full Residential Unit of Use (RUU).

ADUs can get a free bonus RUU (per TRPA Code of Ordinances Section 52.3.4):

  • If the parcel is located within ½ mile of an existing transit stop or a transit stop that will be existing concurrent with the completion of an approved project, or
  • If the parcel is located within ½ mile of a Town Center, or
  • If the parcel is located within a multifamily zone.
    • Additionally, the following two conditions must be met:
      • The ADU or the main house is deed restricted to prohibit the ADU from being converted to tourist use or utilized as a vacation rental, and 
      • The ADU or the main house is deed-restricted for affordable, moderate, or achievable incomes consistent with TRPA Code Section 52.3.4 and Chapter 90, Definitions. Current income thresholds for Bonus Units can be found on TRPA's Housing Webpage under the Residential Bonus Unit Program Section. See:

If you don’t meet the criteria above for free bonus units, property owners would need to provide a Potential Unit of Use (PRUU) with an allocation, or by converting commercial floor area or tourist units. RUUs, PRUUs, and allocations may be available on the open market, or you may contact your local jurisdiction for information about how to obtain an allocation. Please see the TDR marketplace or contact a real estate agent for pricing and availability.


TRPA application fees for projects utilizing bonus units and that are deed-restricted affordable, moderate, or achievable are waived. There is no additional fee for the processing of the deed restriction or bonus unit. Mitigation fees such as mobility mitigation and water quality fees still apply, however, mitigation fee reductions may be available if the property is within low vehicle miles traveled areas. Water quality mitigation fees depend on amount of coverage added and transferred and will be assessed at the time of the permit review. 

  • Under the “General” section of TRPA’s permitting page, find the Project Impact Assessment Online Tool for determining the Mobility Mitigation Fee. The fee varies by location. 
  • See the Mitigation Fee schedule in the “Fees” section of TRPA’s permitting page for other mitigation fees (note the air quality mitigation fee no longer applies).
  • Placer County will not charge impact fees for ADUs smaller than 750 square feet. For a unit that is 750 square feet or more, the impact fees are proportional to the primary unit. School fees still apply to Accessory Dwelling Units that are between 500 and 749 square feet. 


California law requires that ADUs be approved administratively, and local jurisdictions cannot restrict them based on allowable coverage or place income limits on the rental rate of the units, nor can they require deed restrictions be imposed. These stipulations currently conflict with TRPA regulations. Currently ADUs are permitted through a 2-step permitting process. Placer County will review and permit ADUs in accordance with California housing law, and TRPA will review ADU applications in accordance with the TRPA Regional Plan.

  1. Currently, applicants for ADUs shall complete a single-family residential application through TRPA and contact Placer County for local permitting requirements. ADU applicants receive a permit through TRPA and then through Placer County. TRPA's permit review timeline is 30 days for application completeness and 120 days for application review. 
  2. Once the applicant receives a permit from TRPA, the applicant should apply for a building permit from Placer County.

Accessory Home 101

Placer County is here to help you step-by-step during your Accessory Home journey. We offer a variety of resources and information for homeowners interested in building a new Accessory Home or converting an existing structure into an Accessory Home. 

  1. How to Get Started
  2. Calculate Your Cost
  3. View Free Plans
  4. Online Permitting

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.
  • 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.  

Check out Accessory Home 101 for detailed information, FAQs, resources and best practices.