Tuolumne County
Unincorporated Tuolumne County ADU rules
Research summary of what we found for Unincorporated Tuolumne County in Tuolumne County. Not a determination for a specific lot.
City or county ADU page
Unincorporated Tuolumne County ADU page
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Maximum size
A detached ADU may have up to 1,200 sq ft of living area. An attached ADU may add floor area up to 50% of the main home's living area, up to 1,200 sq ft. State law still allows an attached ADU of at least 800 sq ft (Gov. Code § 66321(b)(3)). Square footage may be measured from the interior walls.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, §§ 17.36.050(A), 17.36.030(A)(1)(b)(i), accessed 2026-11-01.
ADU setbacks in Tuolumne County
Setbacks
A detached ADU must be at least 4 ft from the side and rear property lines. An ADU built above an attached or detached garage needs 4 ft side and rear setbacks. No setback is needed when existing living area, a garage or another accessory structure is converted with the same dimensions. No passageway or entrance in view of the street is required.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, § 17.36.050(B), (D), (F), accessed 2026-11-01.
What we found for Tuolumne County
What we have for this place. Where a local figure is stricter than the California state baseline, both are shown.
Local ADU rules
The County's ADU and JADU rules are in County Code Title 17, Chapter 17.36 (Accessory Dwelling Units). The latest amendment shown is Ordinance 3471 (2024); its exact adoption date was not found. ADUs and JADUs are allowed in zones that allow single-family or multifamily homes. The County must act on a complete application within 60 days, without a hearing.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, §§ 17.36.020, 17.36.030(A), (D)(1), accessed 2026-11-01.
ADU types and how many
On a lot with a single-family home: an attached ADU or one inside the home, a JADU inside the home, and a new detached ADU. A JADU may be combined with a detached ADU. On a lot with a multifamily building: ADUs inside non-livable space (such as storage rooms, attics, basements or garages) up to 25% of the existing units, and at least one.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, § 17.36.030(A)(1)-(2), accessed 2026-11-01.
Height
A detached ADU may be 16 ft tall, plus up to 2 ft more if needed to match the main home's roof pitch. Within a half mile walk of a major transit stop, or as part of a multifamily multistory building, a detached ADU may be 18 ft. An attached ADU may be 25 ft or the zone's height limit, whichever is lower, and no more than two stories.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, § 17.36.050(B)-(C), accessed 2026-11-01.
Parking
Parking for an ADU may not be more than one space per unit or per bedroom, whichever is less. It may be tandem on a driveway, or in setback areas where the County allows it. No added space is needed for an ADU built with a new home, within a half mile walk of public transit, in a historic district, inside the home or an accessory structure, where on-street permits are required but not offered, or within one block of a car share vehicle. Garage, carport or covered spaces lost to an ADU need not be replaced.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, § 17.36.050(M), accessed 2026-11-01.
Junior ADUs
A JADU may be up to 500 sq ft of conditioned and unconditioned space, inside the walls of the home (an attached garage counts). It may add up to 150 sq ft only for entry and exit. It needs a separate entrance and an efficiency kitchen with a cooking facility, a food preparation counter and storage cabinets. A deed restriction must be recorded before the building permit, and the JADU may not be sold apart from the home. No parking is needed.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, §§ 17.36.030, 17.36.030(A)(1)(b)(i), 17.36.040(B)-(F), (H), accessed 2026-11-01.
Fees, utilities and rental
No impact fees (including school fees) for an ADU under 750 sq ft; larger ADUs pay in proportion to the main home. No utility connection fee for a JADU. Separate utility meters are needed for a detached ADU, not for an attached one. Both the ADU and the main home need laundry connections. Fire sprinklers are needed only if the main home needs them. An ADU has one kitchen at most and at least one bathroom. It may be rented, but not for less than 30 days, and may not be sold apart from the main home.
Source: Tuolumne County Code Title 17, Chapter 17.36 Accessory Dwelling Units, § 17.36.050(G)-(K), accessed 2026-11-01.
California state rules
The statewide baseline recorded from state law and the HCD ADU Handbook.
Detached size cap described in state law
1,200 sq ft. From Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Side and rear setback cap for a new ADU
4 ft. From Government Code section 66314, which describes a cap on side and rear setbacks for a new ADU.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Setback for a conversion of an existing structure
No additional setback, from Government Code section 66314 for a conversion of an existing structure.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Minimum lot size
A city may not impose a minimum lot size for an ADU, from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Minimum unit the handbook says cities must allow
At least an 800 sq ft ADU with 4 ft side and rear setbacks. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(3).
Source: HCD ADU Handbook, 66321(b)(3); handbook updated March 2026, accessed 2026-10-16.
Detached height described in the handbook
16 ft, or 18 ft or 20 ft in some cases. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(4).
Source: HCD ADU Handbook, 66321(b)(4); handbook updated March 2026, accessed 2026-10-16.
Permit decision deadline
60 days. From Government Code section 66317(a)(3): the permitting agency must decide on (approve or deny) a completed ADU application within 60 days when an existing single-family or multifamily dwelling is on the lot. Section 66317(a)(1) says the application is considered ministerially, without discretionary review or a hearing.
Source: California Government Code section 66317, 66317(a)(1), (a)(3), accessed 2026-10-17.
Owner-occupancy requirement
None. From Government Code section 66315: a local agency may not impose an owner-occupancy requirement on an ADU. It may require that the property be used for rentals of terms 30 days or longer. The HCD ADU Handbook (updated March 2026) describes the same rule.
Source: California Government Code section 66315, 66315; HCD ADU Handbook updated March 2026, accessed 2026-10-17.
Parking near public transit
No parking standards within one-half mile walking distance of public transit. From Government Code section 66322(a)(1). Section 66322(a) lists several other cases where parking standards may not be imposed.
Source: California Government Code section 66322, 66322(a), accessed 2026-10-17.
Ministerial categories
The HCD ADU Handbook (updated March 2026) states that Government Code section 66323 sets four ministerial categories. What we have does not restate those four categories.
Source: HCD ADU Handbook, 66323; handbook updated March 2026, accessed 2026-10-16.
Fire Hazard Severity Zones
If your lot is in a Fire Hazard Severity Zone, the CAL FIRE Office of the State Fire Marshal says in Information Bulletin 25-004 (issued March 3, 2025): “Fire Hazard Severity Zones (FHSZs) should not restrict the development of Accessory Dwelling Units (ADUs). However, additional building standards may be necessary, including but not limited to California Fire Code Chapter 49 and California Building Code Chapter 7A.” State ADU law does not itself bar an ADU there. A city or county may still apply its building code, including wildfire-resistant construction (Gov. Code 66314(d)(8)); require side and rear setbacks “sufficient for fire and safety” for a unit converted under 66323(a)(1); and decline parking in setbacks on specific fire and life safety findings (66314(d)(10)(B)). It may also consider public safety when it designates where ADUs may be permitted (66314(a)). Sprinklers can't be required in an ADU or JADU if the primary residence doesn't need them (66314(d)(12), 66323(d)). Some cities and counties still apply their own fire-zone limits. Where this summary has one, it is listed with the local rules. This summary does not look up your lot. Check the CAL FIRE Fire Hazard Severity Zone map viewer linked from the State Fire Marshal's Fire Hazard Severity Zones page: https://experience.arcgis.com/experience/5065c998b4b0462f9ec3c6c226c610a9
Source: CAL FIRE Office of the State Fire Marshal Information Bulletin 25-004, page 4, issued March 3, 2025; Gov. Code 66314, 66323, accessed 2026-10-20.
State baseline on the directory → · State ADU rules on the homepage →
Can I build an ADU in Unincorporated Tuolumne County?
State law sets a baseline for ADUs in Unincorporated Tuolumne County, and what we found locally is listed on this page. Whether a specific lot can add an ADU depends on zoning, utilities, and other site facts this page does not measure. Confirm with the County of Tuolumne planning department, or run a free address summary.
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