San Bernardino County

Twentynine Palms ADU rules

Research summary of what we found for City of Twentynine Palms in San Bernardino County. Not a determination for a specific lot.

Last checked November 3, 2026.

City or county ADU page

Twentynine Palms ADU page

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How big can an ADU be in Twentynine Palms?

Maximum size
An attached or detached ADU with no bedroom or one bedroom may be up to 850 sq ft. A new detached ADU with more than one bedroom may be up to 1,200 sq ft. The chapter sets no separate figure for an attached ADU with more than one bedroom; state law (Gov. Code § 66321(b)(2)) does not allow a cap below 1,000 sq ft for one. A detached ADU up to 800 sq ft with 4 ft side and rear setbacks must be allowed under state law.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(G)(3)-(4), accessed 2026-11-03.

ADU setbacks in Twentynine Palms

Setbacks
ADUs follow the zone's setbacks, except that side and rear setbacks may be 4 ft. ADUs may not sit in required non-buildable easements. The zone's front setback applies unless it would not leave room for an 800 sq ft ADU with 4 ft side and rear setbacks.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(H), accessed 2026-11-03.

What we found for Twentynine Palms

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

Local ADU rules
Twentynine Palms's ADU rules are in Development Code Chapter 19.134, which Ordinance 311 (adopted September 26, 2023) replaced in full. ADU and JADU applications that meet the chapter are reviewed ministerially, without discretionary review or a hearing, as part of the building permit process. When there is already a home on the lot, the City acts within 60 days of a complete application, and a denial must list what to fix. Nonconforming zoning conditions do not have to be corrected first.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), §§ 19.134.040, 19.134.050(C) (Ord. 311 § 4, 2023), accessed 2026-11-03.

Where ADUs are allowed
ADUs and JADUs are allowed on residential lots zoned for single-family homes with an existing or proposed home. One ADU is allowed on a Mixed Use lot with a single-family home. Detached ADUs and ADUs in non-livable space (such as storage rooms, attics, basements and garages) are allowed on lots with an existing multifamily building. ADUs do not count toward General Plan density.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(A), (F), accessed 2026-11-03.

Height
An ADU may be 16 ft. A detached ADU may be 18 ft within a half mile walk of a major transit stop or high-quality transit corridor, or on a lot with a multistory multifamily building. Two more feet are allowed for a roof pitch that matches the main home. An attached ADU may be 25 ft or the main home's height limit, whichever is lower.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(I), accessed 2026-11-03.

Parking
One off-street space per ADU, which may be tandem on a driveway. No space is needed within a half mile walk of public transit, in a historic district, for an ADU that is part of 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 together with a new home or multifamily building. Garage, carport or covered parking spaces removed for an ADU do not have to be replaced. Junior ADUs need no added parking.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(J), accessed 2026-11-03.

Junior ADUs
A JADU may be 150 to 500 sq ft, entirely inside an existing or proposed single-family home (not in an accessory structure). It needs cooking facilities and its own exterior entrance, and may have its own bathroom or share one with the home. No added parking is needed.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), §§ 19.134.030(F), 19.134.050(G)(2), (G)(5), (J)(4), accessed 2026-11-03.

Utilities, sprinklers and rentals
Fire sprinklers are not needed if the main home does not need them, and adding an ADU does not trigger sprinklers in the main home. Lots without public sewer need a septic system with extra reserve leach area. A separate utility service is allowed only for an ADU on a part of the lot that could legally be split off. ADUs may be rented but not sold apart from the main home. A demolition permit for a detached garage being replaced by an ADU is reviewed and issued with the ADU permit.
Source: Twentynine Palms Municipal Code Ch. 19.134 Accessory Dwelling Units (Municode), § 19.134.050(D)-(E), (G)(7), (K), accessed 2026-11-03.

Contact
The Planning Division is at City Hall, 6136 Adobe Road, Twentynine Palms (760-367-6799 ext. 1008).
Source: City of Twentynine Palms, Planning, Planning page, accessed 2026-11-03.

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.

Starting January 1, 2027: two detached ADUs
Starting January 1, 2027, AB 956 (Chapter 791, Statutes of 2026) raises from one to two the number of new detached ADUs a city or county must allow, without discretionary review, on a lot with a proposed or existing single-family home (Gov. Code 66323(a)). Each may be held to 800 sq ft, 4 ft side and rear setbacks and the state height limits. The city or county does not have to also allow a JADU on a lot where two new detached ADUs have been built. AB 956 also makes HOA and deed rules that effectively prohibit or unreasonably restrict an ADU or JADU void on any lot zoned to allow a single-family home, not only lots zoned for single-family use (Civil Code 4751 and 714.3).
Source: AB 956 (2025-2026), Chapter 791, Statutes of 2026, Gov. Code 66323; Civil Code 714.3, 4751; signed September 29, 2026, accessed 2026-11-03.

Starting January 1, 2027: impact fees above 750 sq ft
No impact fee may be charged on an ADU of 750 sq ft or less, or a JADU of 500 sq ft or less (Gov. Code 66311.5(c)). Starting January 1, 2027, SB 1117 (Chapter 809, Statutes of 2026) changes how fees are figured for larger ADUs: for up to two ADUs on a lot, the proportional impact fee is charged only on the interior livable space above 750 sq ft. On a lot with more than two ADUs, the fee stays proportional to the whole ADU. Utility connection fees and capacity charges are not changed.
Source: SB 1117 (2025-2026), Chapter 809, Statutes of 2026, Gov. Code 66311.5(c); signed September 29, 2026, accessed 2026-11-03.

State baseline on the directory → · State ADU rules on the homepage →

ADU rules near Twentynine Palms

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Can I build an ADU in Twentynine Palms?

State law sets a baseline for ADUs in Twentynine Palms, 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 City of Twentynine Palms Community Development Department (Planning), or run a free address summary.

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