ADU Cost in San Diego — 2026 Guide

The average ADU cost in San Diego ranges from $90,000 for a basic garage conversion to $380,000 for a large detached unit with upgraded finishes. San Diego is more affordable than Los Angeles for ADU construction but still well above the national average, driven by coastal labor premiums, strict energy code requirements, and permit fees that vary significantly between the City of San Diego and unincorporated San Diego County jurisdictions. This guide covers what San Diego homeowners are actually paying in 2026 — not estimates from 2022 articles that haven’t been updated.

Every builder listed on VerifiedADU’s San Diego directory has been CSLB-verified with active licensing, bond coverage, and complaint history checked. But construction pricing is between you and your contractor. This guide gives you the numbers to walk into that conversation informed.

San Diego County issued over 2,700 ADU permits in 2023 — roughly 30% of all new housing permits in the county. That volume generates enough real project data to move beyond guesswork.

Here’s what San Diego homeowners are paying in 2026:

ADU Type	Size Range	Cost Range (2026)	Cost Per Sq Ft
Garage Conversion	200–500 sq ft	$90,000 – $160,000	$275 – $400
JADU	150–500 sq ft	$60,000 – $130,000	$225 – $350
Attached ADU	400–1,200 sq ft	$170,000 – $330,000	$300 – $425
Detached ADU	400–1,200 sq ft	$200,000 – $380,000	$350 – $475
Prefab / Modular	400–1,200 sq ft	$130,000 – $260,000	$250 – $380

These ranges include permitting, site preparation, construction, and standard finishes. They do not include furniture, landscaping, solar panels, or luxury upgrades. Coastal neighborhoods (La Jolla, Del Mar, Encinitas) run 15% to 25% above these averages.

Garage Conversion — $90,000 to $160,000

Garage conversions are the most popular ADU type in San Diego County. The existing structure eliminates foundation and framing costs, making it the fastest and cheapest path to a rentable unit. Most garage conversions in San Diego take 3 to 5 months from permit to occupancy.

A single-car garage conversion (200–300 sq ft) with a kitchenette and bathroom runs $90,000 to $120,000. A two-car garage (400–500 sq ft) with a full kitchen, separate entrance, and in-unit laundry runs $130,000 to $160,000. No replacement parking is required under current California law.

San Diego-specific cost factor: Older garages in neighborhoods like North Park, Hillcrest, and City Heights often lack insulation and have substandard electrical. Budget $10,000 to $20,000 for bringing pre-1970 garages up to current energy code (Title 24) requirements.

JADU (Junior ADU) — $60,000 to $130,000

A JADU converts existing space within the primary home — a bedroom, bonus room, or attached garage — into a separate living unit. JADUs are capped at 500 sq ft and must include a cooking facility. They’re the cheapest ADU option because you’re working within existing walls.

In San Diego, JADUs are particularly common in the older single-story homes throughout Clairemont, Mira Mesa, and Linda Vista where spare bedrooms or large dens can be converted with minimal structural work.

JADU note: Unlike standard ADUs, JADUs may require the property owner to occupy either the primary residence or the JADU.

Attached ADU — $170,000 to $330,000

An attached ADU adds new construction to the existing home — a ground-floor addition, a second-story build-over, or an extension off the back of the house. These projects involve new foundation work (or structural reinforcement), utility tie-ins, and exterior matching.

Second-story ADUs above existing garages are increasingly popular in San Diego’s tighter urban lots, especially in Pacific Beach, Ocean Beach, and the college-area neighborhoods where lot depth is limited. Engineering costs run higher for second-story work due to structural load analysis requirements.

Detached ADU — $200,000 to $380,000

A detached ADU is a standalone structure in the backyard. San Diego allows detached ADUs up to 1,200 sq ft on most single-family lots with 4-foot rear and side setbacks.

San Diego’s year-round mild climate is an advantage here — construction timelines are more predictable than in Northern California, and there’s virtually no weather-related delay risk. A typical 600 sq ft detached ADU on a flat lot in San Diego runs $230,000 to $280,000.

San Diego County cost variations:

• Coastal lots (La Jolla, Del Mar, Carlsbad): Add 15%–25% for Coastal Commission review requirements, higher contractor rates, and premium material expectations
• East County (El Cajon, Santee, Lakeside): Generally 10%–15% below city averages due to lower labor demand and easier site access
• Fire zones (rural east and north county): Add $5,000–$15,000 for fire-resistive construction, ember-resistant vents, and brush clearance requirements

Prefab / Modular ADU — $130,000 to $260,000

Prefab ADUs are factory-built and delivered to the site on a truck. San Diego’s wide suburban streets and relatively flat lots make delivery logistics easier than in LA’s narrow hillside neighborhoods. Several San Diego-based companies — including SnapADU and USModular — specialize in prefab ADU installation throughout the county.

Total installed cost includes the unit, foundation, utility connections, permitting, and site work. Construction time after delivery is typically 2 to 4 months. The City of San Diego has pre-approved several prefab ADU designs through its Standard Plan Program, which can reduce permit review time to as little as 2 weeks.

The City of San Diego Development Services Department handles ADU permits for properties within city limits. Properties in unincorporated San Diego County go through the County Department of Planning and Development Services — a separate process with different fees.

Fee Category	Cost Range	Notes
Building permit	$1,200 – $4,000	Based on project valuation
Plan check fee	$800 – $2,500	65% of building permit fee
School fee	$1,500 – $5,000	$4.79/sq ft for new residential
Sewer capacity fee	$2,000 – $5,000	Varies by sewer district
Water meter / connection	$0 – $5,000	May require new meter for detached ADUs
Impact fees (ADU >750 sq ft)	$0 – $3,000	Waived for ADUs under 750 sq ft
Total permit costs	$3,000 – $12,000	City of San Diego; county fees may differ

Permit timeline: San Diego is required to approve or deny ADU applications within 60 days of a complete submission. The city has been one of the faster California jurisdictions for ADU permitting, with many applications processed in 4 to 8 weeks. Standard Plan ADUs can be approved in as little as 2 weeks.

Fee waiver advantage: San Diego waives development impact fees for ADUs under 750 sq ft, saving homeowners $2,000 to $3,000. This makes smaller ADUs significantly more affordable to permit.

Pre-construction professional services in San Diego typically add $12,000 to $30,000 to the total project cost.

Service	Cost Range
Architectural plans	$4,000 – $12,000
Structural engineering	$2,500 – $6,000
Title 24 energy calculations	$1,200 – $2,500
Soil / geotechnical report	$2,000 – $5,000
Site survey	$1,000 – $2,500
Feasibility / zoning review	$500 – $1,500

Many San Diego ADU builders offer design-build packages that bundle architectural plans, engineering, and permitting into the construction contract. Ask whether a contractor’s per-square-foot quote includes or excludes these soft costs — the answer can swing your total budget by $15,000 or more.

San Diego labor rates are lower than Los Angeles but higher than Sacramento and inland California markets.

• General contractor markup: 15% to 22% of total project cost
• Skilled labor rates: $40 to $75 per hour for electricians, plumbers, and framers
• Material costs: Lumber, concrete, and roofing materials are 8% to 12% above national averages
• Concrete: $150 to $180 per cubic yard delivered (slab foundation for a 600 sq ft ADU requires 15–20 cubic yards)

Labor accounts for 40% to 50% of total ADU construction cost in San Diego. Materials account for 30% to 35%. The remaining 15% to 25% covers permits, soft costs, and contractor overhead. San Diego’s lower labor rates compared to LA mean a typical ADU costs 10% to 20% less than the same unit built in Los Angeles.

These costs regularly surprise San Diego homeowners who budget based on the construction quote alone:

• Coastal Commission review: Properties in the California Coastal Zone — which includes most of La Jolla, Del Mar, Encinitas, Carlsbad, and Oceanside — may require Coastal Development Permits. This adds $3,000 to $8,000 in fees and 2 to 6 months to the timeline.
• Sewer lateral issues: San Diego’s aging sewer infrastructure means many properties need lateral repairs or replacement as a condition of the ADU permit. Cost: $5,000 to $20,000.
• Water pressure upgrades: Some San Diego neighborhoods — particularly in hilly areas of Scripps Ranch, Tierrasanta, and east-county communities — have low water pressure that requires a booster pump for the ADU. Cost: $2,000 to $5,000.
• Brush management (fire zones): Properties in Wildland-Urban Interface zones require defensible space, fire-rated construction, and ember-resistant vents. Common in Poway, Ramona, Alpine, and rural north county. Cost: $5,000 to $12,000 above standard construction.
• HOA restrictions: While California law prohibits HOAs from outright banning ADUs, many San Diego HOAs impose design review requirements that add architectural costs and timeline delays. Budget $2,000 to $5,000 for HOA compliance if applicable.
• Grading and drainage: San Diego’s canyon terrain means many lots require grading work and drainage solutions. Cost: $5,000 to $15,000 for sites with moderate slope.

The California Housing Finance Agency (CalHFA) offers a grant of up to $40,000 to help homeowners cover pre-development costs for ADU construction. This is a grant — no repayment required.

What the $40,000 covers:

• Architectural and engineering plans
• Permits and impact fees
• Soil tests and site surveys
• Title 24 energy calculations

What it does not cover: Construction costs, materials, labor, landscaping, or furniture.

Eligibility for San Diego homeowners:

• Property must be owner-occupied
• Must use a CalHFA-approved lender
• ADU must be on a single-family residential lot
• Income limits apply in some funding rounds
• Must not have previously received a CalHFA ADU grant

In San Diego, where total permit and soft costs typically run $12,000 to $30,000, the CalHFA grant can cover most or all of your pre-construction expenses. For a complete walkthrough, read our CalHFA ADU Grant guide.

San Diego has strong ADU rental economics. Here’s the math for 2026:

ADU Type	Monthly Rent (2026)	Annual Income	Payback Period
Studio / JADU (300 sq ft)	$1,300 – $1,700	$15,600 – $20,400	5 – 7 years
1-bed (500 sq ft)	$1,700 – $2,200	$20,400 – $26,400	8 – 12 years
2-bed (800 sq ft)	$2,200 – $2,800	$26,400 – $33,600	8 – 12 years

A permitted ADU in San Diego typically adds 20% to 30% to a property’s assessed value. On a property valued at $800,000, a 600 sq ft detached ADU could add $160,000 to $240,000 in appraised value — often exceeding the construction cost.

Short-term rental note: ADUs built after January 1, 2025 cannot be used as short-term rentals (less than 30 days) under current California law. San Diego also has its own short-term rental ordinance that restricts Airbnb-style rentals to primary residences. Plan for long-term rental income.

San Diego is consistently 10% to 20% cheaper than Los Angeles for equivalent ADU projects. Here’s how they compare:

Cost Category	San Diego	Los Angeles
Detached ADU (600 sq ft)	$230K – $280K	$280K – $350K
Garage conversion	$90K – $160K	$100K – $180K
Total permit fees	$3K – $12K	$4K – $15K
Skilled labor (per hour)	$40 – $75	$45 – $85
Permit timeline	4 – 8 weeks	8 – 16 weeks

San Diego’s advantage is speed. Faster permitting, milder weather for year-round construction, and fewer hillside complications (outside of specific neighborhoods) mean projects typically finish 2 to 4 months earlier than equivalent LA builds. For a detailed breakdown of LA pricing, see our ADU Cost in Los Angeles guide.

How much does it cost to build an ADU in San Diego?

ADU costs in San Diego range from $60,000 for a basic JADU to $380,000 for a large detached unit in a coastal neighborhood. The average cost for a 500 sq ft detached ADU in San Diego is approximately $230,000 to $280,000 including permits, site work, and standard finishes.

What is the cheapest type of ADU to build in San Diego?

A JADU (junior ADU) is the cheapest at $60,000 to $130,000 because it converts existing space within the home. A garage conversion is next at $90,000 to $160,000. Both avoid new foundation and framing costs.

How long does it take to build an ADU in San Diego?

From permit submission to completion, most ADU projects in San Diego take 8 to 14 months. Permitting typically takes 4 to 8 weeks through the City of San Diego Development Services Department. Construction takes 4 to 8 months for site-built ADUs, or 2 to 4 months for prefab units after delivery.

How much do ADU permits cost in San Diego?

Total permit costs for an ADU in San Diego typically range from $3,000 to $12,000. This includes the building permit, plan check fee, school fees, sewer capacity fee, and any applicable impact fees. ADUs under 750 sq ft are exempt from most development impact fees.

Is it cheaper to build an ADU in San Diego or Los Angeles?

San Diego is 10% to 20% cheaper than Los Angeles for equivalent ADU projects. Lower labor rates, faster permitting, and fewer hillside complications contribute to the difference. A 600 sq ft detached ADU costs $230,000 to $280,000 in San Diego versus $280,000 to $350,000 in LA.

Can I build an ADU in the Coastal Zone in San Diego?

Yes, but properties in the California Coastal Zone may require a Coastal Development Permit in addition to the standard building permit. This adds $3,000 to $8,000 in fees and 2 to 6 months to the timeline. Affected areas include La Jolla, Del Mar, Encinitas, Carlsbad, and Oceanside.

Is the CalHFA ADU grant available to San Diego homeowners?

Yes. The CalHFA ADU grant provides up to $40,000 for pre-development costs including architectural plans, engineering, permits, and surveys. The property must be owner-occupied and you must work with a CalHFA-approved lender. The grant does not need to be repaid.

How much rental income can I earn from an ADU in San Diego?

Monthly rental income for ADUs in San Diego ranges from $1,300 to $1,700 for a studio or JADU, $1,700 to $2,200 for a one-bedroom, and $2,200 to $2,800 for a two-bedroom unit. Annual rental income of $18,000 to $33,000 is typical. ADUs built after January 1, 2025 cannot be used as short-term rentals under current California law.