Shasta County

Unincorporated Shasta County ADU rules

Research summary of what we found for Unincorporated Shasta County in Shasta County. Not a determination for a specific lot.

Last checked October 31, 2026.

City or county ADU page

Unincorporated Shasta County ADU page

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How big can an ADU be in Shasta County?

Maximum size
A detached ADU may be up to 1,200 sq ft (a manufactured home may be slightly larger). An attached ADU, or an ADU made from part of the home, may be up to 50% of the home's living space or 1,200 sq ft, whichever is less, but at least 850 sq ft (1,000 sq ft with more than one bedroom) is allowed in every case. An ADU converted from an existing accessory building may be up to 1,200 sq ft, plus up to 150 sq ft for entry and exit. A JADU may be up to 500 sq ft.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(E)(1), (I)(2)(a), accessed 2026-10-31.

ADU setbacks in Shasta County

Setbacks
Attached and detached ADUs need 4 ft side and rear setbacks. An ADU up to 800 sq ft may sit in the front yard; a larger one follows the zone's front setback. No setback for an ADU converted within an existing building, or rebuilt in the same place and size. No separation from other buildings is required beyond the building and fire codes.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(E)(3), accessed 2026-10-31.

What we found for Shasta County

What we have for this place. Where a local figure is stricter than the California state baseline, both are shown.

Local ADU rules
Shasta County's ADU rules are in County Code § 17.88.132, rewritten by Ordinance 2026-06 (adopted August 25, 2026). ADUs and JADUs are allowed in any zone that allows a home, and size is measured as interior livable space.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(C)-(D), accessed 2026-10-31.

How many ADUs
Every lot with a home may have one attached, detached or converted ADU. On lots in residential, mixed-use and similar zones, the state-law types may be added: one detached ADU up to 800 sq ft with 4 ft side and rear setbacks, one converted ADU, and one JADU. Multifamily lots there may convert up to 25% of the existing units' count from non-livable space (at least one) and add up to eight detached ADUs (not more than the existing units; two with a proposed multifamily building). Guest houses and similar extra dwellings are not allowed on a lot with an ADU, but may be converted to one.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(D)(5)-(6), (I)(1), accessed 2026-10-31.

Height
A detached ADU may be as tall as the zone allows for a home (plus 2 ft to match the home's roof pitch), and never less than 16 ft, or 18 ft within one mile walking distance of a major transit stop or high-quality transit corridor or on a lot with a multistory multifamily building. An attached ADU may be as tall as the zone allows for a home (or the accessory building limit when attached beside an accessory building). A converted ADU or JADU keeps the height of the existing building.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(E)(2), (I)(2)(c), accessed 2026-10-31.

Parking
One off-street space per ADU, which may be in a yard or tandem. None is needed within a half mile walk of public transit, in a historic district, for an ADU inside the home or an accessory structure, where on-street permits are required but not offered, within one block of a car share vehicle, or when the ADU is filed with a new home. Parking removed for an ADU need not be replaced. JADUs need no parking. The Director may waive the parking and access standards for lot constraints.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(E)(6), (G), (I)(2)(b), accessed 2026-10-31.

Design and access
An attached or converted ADU or JADU needs its own entrance, not visible on the same side of the house as the home's main entrance. Exterior colors must match the home (or the building it is attached to) or be neutral, and materials must match, except for manufactured homes and ready-made ADU plans. ADUs need eaves if the home has them, landscaping if the home requires it, and must use the home's driveway connection to the street.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(E)(4)-(5), accessed 2026-10-31.

Junior ADUs
One JADU of up to 500 sq ft inside the home. If it shares a bathroom with the home, the owner must live in the home or the JADU, and the JADU needs an interior door to the home. No owner occupancy is required if it has its own bathroom. No parking is needed.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(D)(4), (E)(4)(f), (J)(2), accessed 2026-10-31.

Rentals, sale, utilities and sprinklers
ADUs and JADUs may not be short-term rentals; rentals must be longer than 30 days. A JADU may not be sold separately; an ADU may be sold separately only under Gov. Code §§ 66341-66342. Water and wastewater must meet Environmental Health rules, and an on-site septic system is allowed if it meets the standards. Fire sprinklers only if the home needs them.
Source: Shasta County Code § 17.88.132 Accessory dwelling units (Ord. 2026-06, Aug. 25, 2026; Municode, codified through Ord. 2026-06), § 17.88.132(K)-(N), (P), accessed 2026-10-31.

Free County ADU plans
The County offers seven free ready-made ADU designs (Castella Modern, Cress, Larkspur, Pacific Crest Cottage, Pine Shed, Twin Peaks and Yarrow), designed for 50 lb and 70 lb snow load zones, with a checklist for the building permit.
Source: Shasta County ready-made ADU plans page, accessed 2026-10-31.

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 Shasta County?

State law sets a baseline for ADUs in Unincorporated Shasta 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 Shasta planning department, or run a free address summary.

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