Why ADU Costs Vary So Much in San Diego
ADU pricing in San Diego swings widely because no two projects share the same combination of property, design, site conditions, and scope. A 600-square-foot detached ADU on a flat lot with existing utility access costs far less than the same size ADU on a hillside lot requiring retaining walls, sewer trenching, and a panel upgrade. Understanding the drivers helps you set a realistic budget before you talk to anyone.
The major cost drivers for San Diego ADU projects:
San Diego-specific factors: San Diego construction labor rates run higher than many inland California markets. Properties in coastal zones face additional review and design requirements. Homes in High or Very High Fire Hazard Severity Zones may need fire-resistant construction materials and ember-resistant vents. SDGE electrical service upgrades and coordination add time and cost compared to simpler utility markets.
ADU Cost Categories: What You Are Actually Paying For
Most homeowners think about ADU cost as a single construction number. The reality is that ADU cost is a collection of categories, and which ones apply to your project depends on the ADU type and your property. Here is what each category covers and what to ask about it.
| Cost Category | What It Includes | Why It Matters | Question to Ask |
|---|---|---|---|
| Feasibility / consultation | Site review, ADU type analysis, rough estimate | Identifies constraints before design spend | What will this cost for my property? |
| Design and plans | Architectural drawings, floor plans, elevations, site plan | Required for permit submittal | Is permit-ready design included? |
| Engineering | Structural, soils report if needed, Title 24 energy | Mandatory for new construction | Do I need a soils report on this lot? |
| Permit and plan review fees | City application, review, and inspection fees | Non-negotiable; paid to the local jurisdiction | What permit fees apply to my project type? |
| Impact and utility connection fees | Water, sewer, electrical connection fees | Units over 750 sq ft pay proportional impact fees | Are impact fees waived for my unit size? |
| Site preparation | Grading, demolition, clearing, access work | Varies widely by lot conditions | What site prep does my property need? |
| Foundation | Slab, raised, piers, or stem wall | Major cost driver for detached and prefab ADUs | What foundation does this design require? |
| Framing / structure | Walls, floor, roof framing for new construction | Not applicable to conversion projects | What framing changes does the design require? |
| Roofing / exterior envelope | Roofing, siding, windows, doors, weatherproofing | Key for detached and attached ADUs | Is roofing included in the quote? |
| Plumbing | Supply, drain, waste, vent, fixtures | Kitchen and bath required; sewer routing adds cost | Where does sewer connection tie in? |
| Electrical | Wiring, panel upgrades, outlets, lighting | Panel upgrades common; SDGE coordination needed | Is my panel adequate or does it need upgrading? |
| HVAC | Heating, cooling, ventilation | Required for habitability in San Diego's climate | What HVAC system is included? |
| Insulation and energy compliance | Wall, roof, floor insulation; Title 24 documentation | California energy code applies to all ADUs | Has Title 24 compliance been factored in? |
| Interior finishes | Drywall, flooring, paint, trim, cabinets | Biggest range in cost based on selections | What finish level does the estimate use? |
| Kitchen and bathroom | Fixtures, cabinetry, counters, tile, appliances | ADU livability depends on quality here | What appliances and fixtures are included? |
| Fire / life-safety features | Smoke and CO detectors, egress windows, fire separation | Required by code; fire zone locations add requirements | Does my property need fire-resistant construction? |
| Inspections | Fees for required inspections during construction | Multiple inspections required at different stages | How many inspections should I expect? |
| Landscaping / access / drainage | Restored landscaping, drainage corrections, path or gate | Often excluded from quotes | What site restoration is included? |
| Contingency | Reserve for unknowns, changes, and surprises | Every ADU project has some unknowns | What contingency do you recommend for my project? |
| Move-in preparation | Appliances, furniture, window coverings, rental setup | Not construction costs, but real budget items | What is excluded that I need to budget separately? |
Not every category applies to every ADU type. A JADU inside your home has a very different cost profile than a new detached ADU in the backyard. Ask your builder which categories are in scope for your specific project.
ADU Cost by Project Type in San Diego
San Diego ADU costs vary by neighborhood, site, and scope. These cost tiers reflect general patterns, not guaranteed ranges. Get project-specific estimates for your property.
| ADU Type | Cost Tier | Common Advantages | Common Cost Risks |
|---|---|---|---|
| Detached ADU | Higher | Maximum privacy; highest rental income potential; most design flexibility | New foundation, full utilities, site access, exterior envelope, fire zone requirements |
| Attached ADU | Mid-high | Shared wall reduces some cost vs. detached; can be substantial size | Structural tie-in, utility extension, may require interior changes to main home |
| Garage Conversion | Mid | No new footprint; reuses existing structure; common path in San Diego | Structural upgrades, insulation, plumbing routing, fire separation, panel upgrade |
| Junior ADU (JADU) | Lower-mid | Reuses existing home space; lowest permit complexity | Limited to 500 sq ft under state law; owner-occupancy required |
| Prefab / Modular ADU | Mid-high (all-in) | Faster build phase; predictable unit price | Foundation, delivery, hookups, permits still required; all-in cost may match stick-built |
| Above-Garage ADU | Higher | Does not use yard space; adds living area vertically | Structural analysis of garage, access design, height compliance, utility routing |
In San Diego, construction labor costs, SDGE electrical service, and fire hazard zone requirements can raise costs compared to inland California markets. A project scoped at one price point in the Central Valley may cost significantly more in San Diego County depending on location and site conditions.
Detached ADU
A freestanding unit built in the backyard or on the lot separate from the main home. It requires a new foundation, full exterior framing and envelope, independent utility connections, and its own HVAC. It offers the most privacy and the highest rental income potential in San Diego, but it also carries the most cost variables. Site access, slope, utility trenching distance, and fire zone status all move the number significantly.
Attached ADU
An addition built onto the existing home and sharing at least one wall. The shared wall can reduce framing and exterior envelope cost compared to a fully detached unit. However, structural tie-in to the main house, utility extension, and any required changes to the main home's layout add cost. This option is common when backyard space is limited but the existing home has a side yard or garage that can be extended.
Garage Conversion
Converting an attached or detached garage to livable space. San Diego homeowners pursue this option because no new footprint is added to the lot. The cost range is wide because a newer, well-built garage in good condition costs far less to convert than an older garage with a cracked slab, low ceiling, undersized electrical, and no plumbing. Confirm the garage's structural integrity, ceiling height, and slab condition before assuming conversion will be the cheapest path.
Junior ADU (JADU)
A unit created within the walls of the existing home, capped at 500 square feet under California state law. It can share a bathroom with the main house and must have a separate entrance. Because no new foundation, exterior structure, or full utility run is required, it typically costs the least. However, owner-occupancy of either the main home or the JADU is required under current state law. The unit still requires permits and must meet habitability and energy code.
Prefab / Modular ADU
A factory-built unit installed on site. The unit price shown by manufacturers does not include foundation, delivery, crane or access equipment if needed, utility connections, permits, or landscaping restoration. For San Diego properties with limited access, steep grades, or fire zone requirements, delivery and site work can be more expensive than for simpler inland lots. Compare all-in quotes, not unit price alone.
Above-Garage ADU
A unit built on top of an existing garage, adding living space without removing yard area. The existing garage structure must be analyzed by a structural engineer to confirm it can support the new load. Access (stairs and egress) must be designed into the project. Height limits may be a factor depending on the property's zoning. This ADU type can be attractive in urban San Diego neighborhoods where lot coverage is limited.
Detached ADU Costs in San Diego
Detached ADUs carry the widest cost range of any ADU type in San Diego because they require the most scope: new foundation, full framing, exterior envelope, independent utilities, and their own mechanical systems. The following factors move the total number most in the local market:
Foundation
The foundation type depends on the site. A flat lot may allow a simple concrete slab. A sloped lot may require a raised foundation, piers, or a stem wall with significant grading. In San Diego, expansive soils in some neighborhoods may require a soils report before foundation design can be finalized.
Utility trenching
Running water, sewer, electrical, and sometimes gas from the main home or the street to the new ADU location requires trenching. Distance, soil hardness, existing hardscape over the route, and depth requirements all affect cost. Longer runs on a large lot cost more than a short connection on a compact urban property.
Electrical service
SDGE (San Diego Gas & Electric) is the local utility. New ADU construction commonly requires a panel upgrade on the main home or a new sub-panel, plus SDGE coordination for the service connection. In some neighborhoods this process involves SDGE inspection and service upgrades that add both cost and lead time.
Fire Hazard Severity Zones
A significant portion of San Diego County falls within High or Very High Fire Hazard Severity Zones, including many hillside and inland neighborhoods. Properties in these zones may require additional fire-resistant materials, ember-resistant vents, specific roofing assemblies, and defensible space compliance. These requirements add cost compared to projects outside fire zones.
Coastal zone requirements
Properties near the San Diego coast may fall within the Coastal Overlay Zone and may require a Coastal Development Permit in addition to a standard building permit. The California Coastal Commission has jurisdiction over some coastal properties. Coastal design and review requirements affect both timeline and cost.
Published cost-per-square-foot estimates for San Diego detached ADUs vary widely in professional sources and builder websites. Always request a site-specific estimate from a licensed builder rather than applying a statewide or national average to your project.
Looking for builders who specialize in detached ADUs in San Diego? Compare San Diego ADU builders by project type, service area, and rating.
Garage Conversion ADU Costs in San Diego
Garage conversions are among the most common ADU projects in San Diego because they reuse an existing structure without adding a new building footprint. They also frequently cost less than building from scratch. But the cost range is wide, and many homeowners are surprised by what a garage conversion actually requires.
Existing garage condition
The starting condition determines the scope. A newer, well-built garage with a level slab, adequate ceiling height, and a panel with room to grow is a much simpler conversion than a 1960s garage with a cracked slab, 6'8" ceiling, and 60-amp service feeding the main panel.
Ceiling height
California requires a minimum ceiling height of seven feet for habitable rooms. Many older garages fall below this threshold, requiring the slab to be lowered, the roof to be raised, or the project to be approached differently. This is a common cost surprise.
Plumbing
Adding a bathroom means adding a drain line, which typically requires cutting through the concrete slab. Sewer routing to the existing lateral and the cost of that work depend on where the ADU bathroom will be positioned relative to the existing sewer connection.
Electrical panel
Garage conversions commonly require a panel upgrade or a new sub-panel to support the added load: lights, outlets, kitchen appliances, HVAC, and EV-ready wiring if required. In San Diego, SDGE coordination may extend the timeline.
Fire separation
If the garage is attached to the main home, code requires fire separation between the new ADU and the primary dwelling. This typically involves fire-rated drywall, fire-rated door assemblies, and compliant penetration sealing.
Insulation and energy
Garage walls and ceilings are rarely insulated to residential standards. Meeting Title 24 energy code for a habitable space requires wall, ceiling, and sometimes floor insulation, plus potentially window and door upgrades.
Moisture
Concrete slabs in older San Diego garages may lack proper vapor barriers. Moisture issues discovered during construction add remediation cost.
Garage conversions are not automatically simple or cheap. A two-car garage with older concrete, low ceiling clearance, and an undersized panel can cost nearly as much as a modest detached ADU after all required upgrades are factored in.
For a deeper look at garage conversion ADUs in San Diego, including what the permit process involves and what questions to ask a builder, see the garage conversion ADU guide.
Prefab and Modular ADU Costs in San Diego
Prefab and modular ADUs are built in a factory and installed on site. The build phase is often faster than stick-built construction, and the unit price can be easier to predict early in the process. However, the unit price is not the project price.
For any prefab ADU in San Diego, homeowners should budget separately for:
- •Foundation: slab or raised foundation appropriate for the site
- •Site preparation: grading, clearing, and access for delivery
- •Delivery and placement: crane or flatbed delivery may be needed depending on lot access and unit weight
- •Utility connections: water, sewer, electrical, and gas hookups from the existing property to the unit
- •SDGE coordination: electrical service connection and any required panel work
- •Permits: site-specific building permit, plan review, and inspections still required
- •Landscaping restoration: site work after installation often disrupts surrounding area
When comparing prefab and stick-built quotes, make sure both include the same scope — foundation, utilities, permits, and site work. A prefab quote that excludes these items can look much lower than a stick-built quote that includes them, while the all-in cost ends up similar or higher.
Some San Diego sites add additional cost for prefab specifically: hillside lots with limited crane access, fire zone requirements that affect the unit's material spec, and longer utility runs on larger coastal properties. Discuss these factors with the manufacturer and with a local builder before committing to a unit.
Learn more about prefab ADU options and considerations at the prefab ADU guide for San Diego.
Permit, Design, and Professional Fees
Soft costs are the expenses outside of physical construction that homeowners most often underestimate. They can represent 15 to 25 percent or more of total project cost depending on project complexity and what the builder includes.
Design fees: Architectural drawings, site plan, floor plans, elevations, and sometimes 3D renderings. Fees vary widely based on project type and firm. Since January 2025, California law has required cities to offer pre-approved ADU plan sets, which may reduce design cost for eligible projects.
Engineering fees: Structural engineer for new construction or significant structural changes. Title 24 energy compliance consultant for all residential projects. Soils or geotechnical engineer if the site has slope, expansive soil, or unusual conditions — more common in certain San Diego neighborhoods.
Permit application and review fees: Paid to the City of San Diego Development Services Department or the applicable local jurisdiction. Fees vary by project valuation and ADU type. Confirm the current fee schedule with the City before budgeting.
Impact and utility connection fees: Water and sewer connection fees, electrical service connection fees. California SB 13 exempts ADUs of 750 square feet or less from development impact fees statewide. Larger units pay proportional fees. Utility connection fees are separate from impact fees and are charged by the utility or city depending on the type of connection.
Plan check corrections: If the City issues correction comments after reviewing your submittal, additional professional time is required to respond and resubmit. Multiple correction rounds are not unusual on complex projects.
Ask every builder or designer upfront: what professional fees are included in your quote and which am I responsible for separately? The San Diego ADU Permit Guide covers the full permitting process in detail. Read the permit guide.
Utility and Site Work Costs in San Diego
Utility and site work costs are the budget category homeowners most consistently underestimate. Two ADUs with identical floor plans can have very different total costs if their sites differ in topography, access, utility proximity, and condition.
Water
New water service connection or extension to the ADU. Cost depends on distance from the nearest meter or main, the required pipe size, whether a new meter is needed, and whether existing supply lines must be upgraded. Some San Diego jurisdictions require separate meters for new ADUs.
Sewer
Lateral connection or tie-in to the existing sewer line. In some older San Diego neighborhoods, sewer laterals are aging and may require inspection and repair as a condition of the new connection. For detached ADUs on larger lots, the trenching run from the ADU to the main sewer can be substantial. Slab penetrations for garage conversions add cost depending on bathroom placement.
Electrical (SDGE)
New circuits, a sub-panel, or a main panel upgrade are common in San Diego ADU projects. SDGE is the local investor-owned utility. Coordination with SDGE for service connections takes time and sometimes requires SDGE inspection before the final building department inspection. Properties in older neighborhoods with 100-amp service may need a full panel upgrade before the ADU can be energized. California also requires EV-ready outlets and may require solar-ready conduit depending on project type.
Gas
If the ADU uses gas appliances such as a range, water heater, or furnace, a gas line extension is required from the existing service. If the design uses all-electric appliances, this category drops out of scope.
Trenching
Underground utility runs require trenching. Cost depends on distance, soil conditions (some San Diego soils are rocky or expansive), whether hardscape such as driveways or patios must be cut and replaced, and required trench depth. Long runs on large lots can add meaningful cost compared to compact urban properties.
Grading and drainage
San Diego properties range from flat coastal lots to steep hillside parcels to canyon-adjacent land. Sites requiring grading, retaining walls, or drainage corrections add cost. Stormwater management may require engineering and documentation depending on the site and project scope.
Site access
Equipment — excavators, concrete trucks, delivery vehicles — needs physical access to the build site. Restricted access through narrow passages, low gates, or steep grades limits the equipment that can be used and may require hand-work or specialized equipment that costs more.
Demolition
If a structure needs to be removed before the ADU can be built, or if a garage conversion requires selective demolition of existing finishes or slabs, demolition adds cost. Material disposal fees in San Diego add to demolition budgets.
Two ADUs with similar floor plans can have very different total costs if one has easy utility access and a flat lot while the other requires long trenching runs, a panel upgrade, and sloped site work. Site conditions matter as much as design.
Hidden and Overlooked ADU Costs
These items are not always included in base quotes and are frequently missing from early budget conversations. Ask about each one before you commit.
Always ask: what is NOT included in this quote? The exclusions tell you more than the line items do.
How to Compare ADU Quotes in San Diego
ADU quotes can look very different even for similar projects because they cover different scopes. Comparing the bottom line number without reviewing what each quote includes and excludes is one of the most common budget mistakes homeowners make.
For each written quote, verify and compare:
Not sure which San Diego ADU builders to compare? Compare San Diego ADU builders by project type and service area, or submit your project details to get matched with qualified local professionals.
ADU Financing Options in San Diego
How you finance an ADU affects what you can build, when construction can start, and what it costs you monthly over time. Here are the most common options San Diego homeowners use.
Cash savings
Paying out of pocket avoids debt and interest. It requires liquid capital and may not be available for larger projects. Some homeowners combine savings with another financing source to cover the full project cost.
HELOC (Home Equity Line of Credit)
A revolving line of credit secured by home equity. Variable interest rate. The draw schedule aligns well with construction payment milestones. San Diego homeowners with significant equity may qualify for a HELOC that covers most or all of a project. Rates fluctuate; confirm current terms with your lender.
Home equity loan
A fixed-rate lump-sum loan secured by home equity. Works well when the total project cost is known. Monthly payments are fixed, which makes budgeting predictable. Compare rates and terms from multiple lenders.
Cash-out refinance
Replaces the existing mortgage with a larger loan and uses the difference for the ADU. Makes financial sense when the new interest rate is favorable compared to the existing mortgage rate. Rate environment matters significantly for this option.
Construction loan
Short-term financing that covers the build phase, typically converting to a permanent mortgage at completion. Requires more documentation than other options. Lenders may require builder licensing verification and project plans as part of the underwriting process.
Renovation loan (FHA 203k, Fannie Mae HomeStyle)
Wraps renovation costs into a purchase or refinance mortgage. Useful for homeowners who are purchasing a property and plan to add an ADU, or for garage conversion and JADU projects. Eligibility requirements and property conditions apply.
CalHFA ADU programs
The California Housing Finance Agency has offered ADU-specific loan programs for eligible homeowners. Program availability, terms, and eligibility requirements change. Check with CalHFA directly for current program status.
This is not financial advice. Homeowners should speak with licensed lenders, financial advisors, and tax professionals before making financing decisions. Loan products and program availability change; confirm current options with your lender before relying on any information here.
How to Set a Realistic ADU Budget in San Diego
A realistic ADU budget accounts for all cost categories, not just construction. Working through this process before getting quotes helps you evaluate proposals more clearly.
- 1
Define your ADU goal
Rental income, housing a family member, home office, or guest space. The goal affects the size, design, and finish level you actually need.
- 2
Choose your ADU type
Based on your lot, existing structures, budget range, and goal. A JADU inside the home and a detached ADU in the backyard have very different cost and complexity profiles.
- 3
Estimate rough size
What square footage does this ADU actually need to serve its purpose? Larger units cost more to build, maintain, and may cross the 750-square-foot impact fee threshold.
- 4
Identify site constraints
Slope, soil conditions, utility proximity, access for equipment, coastal or fire zone overlays. These factors often determine cost more than design choices.
- 5
Ask what is included and excluded
Get this in writing from every builder. Compare scope, not just price.
- 6
Budget for design and engineering
Separately from construction if your builder does not provide these services. Ask upfront.
- 7
Budget for permit fees
Confirm the current City of San Diego DSD fee schedule or the schedule for your local jurisdiction. These are paid to the City and are non-negotiable.
- 8
Budget for utility connections
Water, sewer, electrical, and SDGE service work. Ask each builder what utility scope is included.
- 9
Set a contingency
Ask your builder what contingency is appropriate for your project type. Projects with unusual sites, older structures, or complex scope typically warrant a higher contingency.
- 10
Confirm your financing path
Talk to a lender before committing to a project cost. Financing affects what you can actually proceed with.
- 11
Request written proposals
From at least two qualified builders. Compare line by line.
- 12
Verify credentials
License through the California Contractors State License Board, current insurance certificates, and references from recent ADU projects in San Diego.
Red Flags in Low ADU Quotes
A lower quote is not always a better deal. When one quote comes in significantly below others, the difference is usually scope, not efficiency. Before accepting any quote, check for these warning signs:
Quote is significantly lower than all others without explanation
Missing scope is almost always the reason. Ask what is excluded.
No written scope of work
If it is not in writing, it is not included.
Permit responsibility is not addressed
Who submits, who responds to corrections, who schedules inspections? Unclear permit responsibility leads to conflict mid-project.
No utility or site work detail
A quote that does not address sewer, electrical, and site access is not a complete project price.
No mention of engineering or design services
Either they are excluded, or the builder does not know they are required.
Finish allowances that are unrealistically low
Low allowances force homeowners into change orders when they make actual selections.
Large upfront deposit before permits are issued
Permits first, deposits later is a reasonable expectation. Large upfront payments before work can legally begin are a risk.
No change order process or pricing
Every project has some changes. A builder without a change order process usually handles changes informally, which causes disputes.
No ADU-specific project references or portfolio
ADU permitting and construction is different from general home improvement. Ask for recent ADU projects specifically.
License cannot be verified through the CSLB
Check any contractor's license at the California Contractors State License Board before signing anything.
The lowest quote may become the most expensive project once change orders, missing scope, and permit problems are added in. Ask questions before you sign.
Questions to Ask ADU Builders About Cost
Bring this checklist to every builder conversation:
- 1.What is included in this estimate?
- 2.What is explicitly excluded?
- 3.Does this include architectural design and permit-ready plans?
- 4.Does this include structural engineering?
- 5.Does this include permit support, correction responses, and inspection scheduling?
- 6.Does this include utility connections — water, sewer, electrical, and gas?
- 7.Does this include site work, grading, or drainage?
- 8.What finish and appliance allowances are built in, and what are the dollar amounts?
- 9.What commonly drives change orders on projects like this?
- 10.How do you handle unexpected site conditions such as poor soil or a defective sewer lateral?
- 11.What is your payment schedule and what triggers each payment?
- 12.Can I see a recent ADU project with a similar scope in San Diego or a nearby city?
- 13.Do you have experience working in my specific city or neighborhood?
- 14.What warranty do you provide on labor and materials?
San Diego ADU Budget Checklist
Use this checklist before signing any ADU contract.
- 1.Define your ADU goal and identify which type fits your property and budget
- 2.Confirm your jurisdiction (City of San Diego, Chula Vista, Carlsbad, another city, or unincorporated County)
- 3.Review current permit requirements and fee schedules with your local building department
- 4.Identify site constraints: slope, soil conditions, utility proximity, equipment access, overlays
- 5.Estimate design and engineering fees separately from construction costs
- 6.Request itemized written estimates from at least two qualified ADU builders
- 7.Compare quotes line by line, including exclusions
- 8.Confirm in writing who is responsible for permit support and utility coordination
- 9.Budget for utility connections and any panel or sewer upgrades
- 10.Set a contingency appropriate for your project type — ask your builder what they recommend
- 11.Confirm your financing path with a licensed lender before committing to a project cost
- 12.Verify CSLB license and current insurance certificates for all contractors
- 13.Check references from recent ADU projects in the San Diego area
- 14.Keep all written contracts, plans, permits, and inspection records
Frequently Asked Questions
How much does an ADU cost in San Diego?+
What is the cheapest type of ADU to build in San Diego?+
Is a garage conversion cheaper than a detached ADU in San Diego?+
Are prefab ADUs cheaper in San Diego?+
Do ADU quotes include permit costs in San Diego?+
Do ADU quotes include utility connections in San Diego?+
How much should I budget for ADU design and plans in San Diego?+
Can I finance an ADU in San Diego?+
Does an ADU increase property value in San Diego?+
Can I rent out my ADU in San Diego?+
Why are ADU quotes so different from builder to builder in San Diego?+
What ADU costs are most commonly overlooked in San Diego?+
How many ADU quotes should I get in San Diego?+
Before you hire anyone
Verify contractor licensing through the California Contractors State License Board at cslb.ca.gov. Confirm current general liability and workers' compensation insurance. Check references from recent ADU projects — not just general renovation work. Read every exclusion in the written contract before signing.
Reminder: This guide is for general informational purposes only and is not financial, legal, tax, architectural, engineering, construction, or permitting advice. ADU costs vary based on your property, design, site conditions, jurisdiction, utilities, financing, materials, labor, and builder scope. Confirm current requirements with the City of San Diego or your local jurisdiction and consult qualified professionals before making decisions.
Sources and Official Resources
- •California Department of Housing and Community Development — ADU Handbook — California HCD. hcd.ca.gov/policy-research/accessory-dwelling-units. Last accessed June 2026. Confirm current versions before relying on them.
- •City of San Diego Development Services Department — ADU and JADU Resources — City of San Diego DSD. sandiego.gov/dsd/homeowners/adu. Last accessed June 2026. Confirm current versions before relying on them.
- •California Contractors State License Board — Contractor License Verification — California CSLB. cslb.ca.gov. Last accessed June 2026. Confirm current versions before relying on them.
- •California Housing Finance Agency — ADU Financing Resources — CalHFA. calhfa.ca.gov — confirm current program availability directly with CalHFA. Last accessed June 2026. Confirm current versions before relying on them.
- •California Government Code §§ 65852.2 and 65852.22 — ADU and JADU State Law — California Legislature. leginfo.legislature.ca.gov. Last accessed June 2026. Confirm current versions before relying on them.
This guide draws on official California state law provisions, City of San Diego Development Services Department resources, and published professional guidance current as of June 2026. ADU regulations, fees, and market conditions change. Always verify with the applicable building department and qualified professionals before starting a project.