Everything homeowners ask about building an ADU in San Diego — answered with 2026 data.
Yes, ADUs are allowed in Every base zone and Planned District zone whose use table lists ADUs as a limited use, which is generally every zone that allows residential use, including multiple-dwelling and mixed-use commercial zones (SDMC 141.0302; IB-400). JADUs are allowed only in single-dwelling-unit zones, or on a lot in a multi-unit zone that holds a previously conforming single-family home. Check your zone, Coastal Overlay, fire hazard and transit-priority status on the city's ZAPP map in San Diego, CA. The maximum size for a detached ADU is 1,200 sq ft gross floor area (minimum 150 sq ft) for a new attached or detached ADU (SDMC 141.0302(b)(7)). ADU floor area counts toward the lot's floor area ratio, but one ADU of 800 sq ft or less is always allowed and is exempt from FAR, lot coverage, front setback and open-space rules (141.0302(b)(4)). Garage or carport space under an ADU and an exterior-access mechanical closet do not count toward the 1,200 sq ft (DSD FAQ). Attached ADUs can be up to Same 1,200 sq ft cap as detached. A conversion of space inside the existing house or an existing accessory structure has no size cap and may add up to 150 sq ft for entry and egress. San Diego has an ADU-friendliness score of 9/10. Check our full San Diego ADU rules page for complete zoning details.
ADU construction in San Diego typically costs $250,000-$450,000. The cost per square foot averages $375-$600. Garage conversions are more affordable at $80,000-$200,000, while prefab ADUs cost $170,000-$325,000. Permit fees add IB-501 (August 2026), Table 501A: a detached ADU of 500 sq ft or less, or an attached ADU or JADU up to 1,100 sq ft, pays $3,512.92 plan check plus $2,228.29 inspection for the first 500 sq ft ($5,741.21) and $6.98 + $4.46 per sq ft above that (about $9,173 for an 800 sq ft attached unit). A detached ADU over 500 sq ft is billed at the single-dwelling-unit rate: $8,085.26 plan check plus $8,401.90 inspection ($16,487.16 flat up to 3,000 sq ft including attached accessory structures). Every project also pays the $737 General Plan Maintenance Fee, a $12.16 mapping fee, a 2.5-hour DIF-calculation review (about $442 at the $176.84 hourly rate), $529.71 per new address, water/sewer plan check of $176.57 (no meter change) or $353.13 (new meter), and state seismic and building-standards fees. School district fees apply to any ADU of 500 sq ft or more (IB-146). Express plan check costs $793.95 plus 1.5x the regular plan check fee to your budget. See our detailed San Diego ADU cost guide.
Detached ADUs in San Diego can be up to 1,200 sq ft gross floor area. Attached ADUs are limited to Same 1,200 sq ft cap as detached. A conversion of space inside the existing house or an existing accessory structure has no size cap and may add up to 150 sq ft for entry and egress. Junior ADUs (JADUs) have a cap of 150 to 500 sq ft, inside an existing or proposed single-family home or its attached garage; may expand the house by up to 150 sq ft for entry (141.0302(c)). JADU floor area does not count toward FAR. A detached garage cannot become a JADU. Maximum height is Two stories for a detached ADU or an ADU on an existing accessory structure on a single-dwelling-unit lot; otherwise the ADU follows the base and overlay zone height limit (141.0302(b)(8)). RS-1-1 through RS-1-7 zones allow 24 ft at the setback line rising to 30 ft under the angled building envelope plane (Table 131-04D; SDMC 131.0444); the 30-ft Coastal Height Limit applies near the coast. There is no separate 16-ft or 25-ft ADU cap. You are allowed up to Single-family lot: 1 conversion ADU inside the house or an existing accessory structure + 1 new attached or detached ADU + 1 JADU on a qualifying lot.
Rear setback: None for an ADU 16 ft or lower outside a High or Very High Fire Hazard Severity Zone; the Building Code's fire-separation rules may still push the wall off the line. Over 16 ft next to a residential lot: 4 ft or the zone's rear setback, whichever is less. In a High or Very High Fire Hazard Severity Zone: 4 ft at any height (141.0302(b)(9)(C)-(D)). Conversions and same-footprint rebuilds keep the existing structure's setbacks (141.0302(a)(5)). Side setback: Interior side: same rule as rear, none at 16 ft or under outside fire hazard zones, 4 ft (or the zone minimum if less) over 16 ft next to residential, 4 ft in High/Very High fire zones. Street side: 4 ft or the zone's street-side setback, whichever is less (141.0302(b)(9)(B)). Exterior stairs, decks and balconies must meet the full base-zone setback (DSD ADU page). Front setback: The base zone's front setback applies (15 to 25 ft in RS-1 zones, Table 131-04D), except that one ADU of 800 sq ft or less may encroach into the front yard (141.0302(b)(4); IB-400). JADUs keep the setbacks of the main house. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None required for any ADU or JADU (141.0302(b)(10)(A), (c)(7)(A)). The one exception is a lot inside the Beach Impact Area of the Parking Impact Overlay Zone and outside a transit priority area, where one space is required per ADU unless the unit is 500 sq ft or less, attached, in a historic district, in a residential permit parking district, or within a block of a car-share vehicle. No replacement parking when a garage or carport is converted or demolished, except in that same Beach Impact Area. Bonus and affordable ADUs outside a transit priority area need one space each (141.0302(d)(6)). A driveway shorter than 18 ft after a garage conversion must be closed. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for an ADU (141.0302(b)(11)). A JADU requires the owner to live in the house or the JADU only when the JADU shares a bathroom with the house; a JADU with its own bathroom has no owner-occupancy rule (AB 1154, applied in IB-400 January 2026). A recorded JADU agreement is required before the permit issues (141.0302(c)(1)(F)). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in San Diego is typically State law: the city must approve or deny within 60 days of a complete application or the ADU is deemed approved (Gov. Code 66314, SB 543 effective January 1, 2026); pre-approved plans get a 30-day review (IB-400). DSD's live dashboard on September 18, 2026 showed about 2 days in intake, 12-18 calendar days for a first review (Structural 12, Combined 16, Planning and Engineering 18), 6-13 days per recheck and 2 business days for issuance; expect one or two correction cycles. Plan check: Fully digital plan check through the DSD online portal, with a single consolidated resubmittal after all disciplines finish a cycle. Fire sprinklers are required only if the main house has them; a detached ADU never triggers sprinklers in the existing house (141.0302(a)(6)); all bonus and affordable ADUs must be sprinklered (141.0302(d)(5)). A new detached, site-built ADU must include solar panels under the California Energy Code (they may go on the main house); conversions and JADUs are exempt. An ADU over four units on a lot triggers Mobility Choices review, and every ADU needs code-compliant refuse and recycling storage (SDMC 142.0801). Pre-approved plans availability: Yes. Under AB 1332 the city accepts three outside catalogs of pre-approved plans, the County of San Diego Standard ADU Plans, the City of Chula Vista Standard ADU Plans and the City of Encinitas Permit-Ready ADU Plans, with a 30-day review; the plans must be licensed from their designer and re-checked against current codes and the SDMC development standards (DSD ADU page; IB-400). Applicants may also have their own plans pre-approved for others through the master plan process in IB-114a; the city does not publish a count of such plans.
Average ADU rental income in San Diego: 1-bedroom units rent for $2,200-$2,700/month, 2-bedroom units for $3,000-$3,300/month. Short-term rentals: No. An ADU may not be rented for less than 31 consecutive days (SDMC 141.0302(a)(8)); a JADU must be rented for longer than 30 days and may not be used for Short-Term Residential Occupancy (IB-400; AB 1154). Expected ROI: 6-10% gross rental yield on a $250,000-$450,000 detached build at $2,200-$2,700/mo (5.9-13% on the raw ranges), before vacancy, taxes and financing; a garage conversion costs a third to a half as much and yields proporti.
The minimum lot size for an ADU in San Diego is No minimum lot size for an ADU (141.0302(b)(5)) or a JADU (141.0302(c)(2)); ADUs and JADUs are also exempt from the zone's density limit. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In San Diego, a garage conversion typically costs $80,000-$200,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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