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How Long Does It Take to Build an ADU in San Diego? (2026 Timeline)
ADU Timeline Guide · San Diego · 2026

How Long Does It Take to Build an ADU in San Diego?

The real answer: 10–12 months for a typical detached ADU, start to finish. Here's every phase, what eats the most time, and the one delay most contractors don't warn you about.

By IL Total Design & Build · CSLB #1058676 · Last updated May 2026

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Completed detached ADU in Poway, San Diego — designed and built by IL Total Design and Build
Completed detached ADU in Poway, San Diego — designed, permitted, and built by IL Total Design & Build

The most common question we get before a project kicks off is some version of: "How soon can we have this thing built?" The honest answer isn't what most contractors give you — a vague "6 to 18 months" that covers everything from a garage conversion to a two-story custom ADU. This guide gives you real phase-by-phase numbers based on what we see on actual San Diego projects, plus the one delay that catches more homeowners off guard than any other.

Quick answer — timeline at a glance

A typical detached ADU in San Diego takes 10–12 months from first consultation to move-in ready. That breaks down as: design and drawings (10–16 weeks), city permitting (60–90 days), construction (3–5 months), and final inspections (2–4 weeks). The single biggest wildcard is San Diego Gas & Electric — a new meter/service connection can add 6–12 weeks to your project and there is no way to rush it.

The 10–12 month picture

Here's roughly how the phases stack against each other on a typical project. Some overlap is possible — for example, your contractor can begin site prep while final permit corrections are processed — but plan conservatively until your permit is in hand.

Design
10–16 weeks
Permitting
60–90 days
Construction
3–5 months
Final / CO
2–4 wks
Total: 10–12 months for a typical detached ADU · Garage conversions often run faster (6–9 months) · Two-story or coastal projects may run longer (12–18 months)

Phase 1: Feasibility & design

1
Feasibility & Design
10–16 weeks

This phase covers everything from your first site visit through permit-ready drawings. It's longer than most people expect because every IL Total Design & Build project starts from scratch — we don't use stock floor plans. Custom design means your ADU is built for your specific lot, your setbacks, your existing structures, and your goals. That takes time to do right.

What happens in this phase:

  • Initial feasibility consultation and site assessment
  • Zoning and setback verification (lot coverage, FAR, height limits)
  • Architectural design and floor plan development
  • Structural engineering calculations
  • Title 24 energy compliance documentation
  • Final permit-ready drawing set

The 10–16 week range is wide because complexity drives it. A straightforward 600 sq ft detached unit on a flat lot in a standard zone moves faster than a hillside lot with retaining walls, a coastal zone setback constraint, or a unit requiring a new electrical service.

Your role in this phase: Attend design reviews, make decisions on layout and finishes, respond to questions from your architect. Slow decision-making on your end is one of the most common causes of design phase overruns — the faster you give feedback, the faster drawings move.

Phase 2: City permitting

2
Permit Submission & Approval
60–90 days

California law requires cities to approve or deny a compliant ADU application within 60 days. In practice, the City of San Diego typically hits that window on well-prepared submissions — but "well-prepared" is doing a lot of work in that sentence. Applications with incomplete documents, missing calculations, or plans that don't reflect the actual site conditions will come back with correction letters, and each round adds 2–4 weeks.

The City of San Diego also operates a pre-approved plan program (AB 1332) that can cut permit time to approximately 30 days. Because IL Total projects are fully custom, we submit standard applications — but a clean, complete first submission typically resolves in 60–90 days without multiple correction rounds.

What happens in permit review:

  • Pre-screen: city confirms all required documents are included (2–4 weeks)
  • Plan check: structural, zoning, fire, energy compliance reviewed
  • Correction letter (if issued): typically 1–2 rounds on complex projects
  • Fee payment and permit issuance
Coastal Zone note If your property is in the Coastal Zone (La Jolla, Pacific Beach, Ocean Beach, Del Mar, Solana Beach, etc.), you'll need a Coastal Development Permit in addition to standard building permits. AB 462 requires CDP approval within 60 days — but coastal review runs in parallel, not in series, so the added time depends on your jurisdiction. Plan for 30–60 additional days if coastal permits apply.
Your role in this phase: Mostly waiting. Your contractor and designer handle corrections and resubmittals. Your main job is to be reachable if city reviewers have questions about owner intent, and to sign permit applications as required.
ADU construction in progress in San Diego by IL Total Design and Build
ADU framing and construction underway — IL Total Design & Build, San Diego

Phase 3: Construction

3
Construction
3–5 months

Construction for a standard detached ADU (roughly 400–900 sq ft) runs 3–5 months once the permit is issued and the site is mobilized. This is faster than most homeowners expect — but it's also the phase where the SDG&E wildcard hits hardest (more on that below).

Typical construction sequence:

  • Site prep & foundation: grading, trenching, slab or pier work (2–5 weeks depending on soil and site conditions)
  • Framing: walls, floors, roof structure (2–4 weeks)
  • Rough mechanicals: plumbing, electrical, HVAC rough-in, sheathing, windows (3–6 weeks)
  • Inspections at rough stage (city inspectors must approve before closing walls)
  • Insulation, drywall, interior finishes: flooring, cabinets, fixtures (4–8 weeks)
  • Exterior: siding, roofing, paint, landscaping restoration
  • Utility connections: water, sewer, electrical service (timeline varies — this is the big one)

Two-story ADUs, units with complex rooflines, or projects requiring significant site work (retaining walls, extensive grading) can push construction to 5–7 months. Garage conversions tend to run faster — often 2–3 months of active construction — because the structure already exists.

Your role in this phase: Stay accessible for finish selections (tile, flooring, fixtures) — late decisions here cause real schedule delays. Walk the site periodically with your project manager. Make sure access to the site is available for deliveries and subcontractors.

Phase 4: Final inspections & certificate of occupancy

4
Final Inspections & CO
2–4 weeks

Once construction is substantially complete, the city conducts final inspections covering structural, electrical, plumbing, mechanical, energy compliance, and accessibility. If all inspections pass, the city issues a Certificate of Occupancy — the legal document that makes the ADU habitable and rentable.

Most projects close out final inspections in 2–4 weeks. Common reasons it takes longer: a punch list item identified at inspection requires correction before re-inspection is scheduled, or utility connections aren't finalized before the city will issue the CO.

When can you start renting? You cannot legally rent the ADU until the Certificate of Occupancy is issued — not when construction looks done, not when the inspector does a walk-through. Plan your tenant timeline around the CO date, not the construction completion date.

Estimate your ADU timeline

Select your project type to get a rough timeline range based on our experience with San Diego projects.

ADU Timeline Estimator

Select your project type:

Estimates based on typical San Diego projects. Your actual timeline depends on site conditions, city workload, HOA requirements, and how quickly decisions are made. Book a free feasibility check for a project-specific estimate.

What causes delays — and how long they add

Every ADU project has some slack in the schedule. Most delays are manageable. But one delay consistently catches San Diego homeowners off guard and there's essentially nothing you can do to speed it up.

Most impactful delay
SDG&E new meter / service connection
Adds 6–12 weeks

If your ADU requires a new electrical service connection — its own meter, not shared with the main home — SDG&E's processing and installation backlog adds 6 to 12 weeks with no ability to expedite. This is the delay that surprises homeowners most. It's not the city, it's not your contractor — it's the utility, and their queue is their queue. The fix: get the SDG&E application submitted as early in the project as possible, ideally concurrent with permit submission, not after.

Common delay
Permit correction rounds
Adds 2–6 weeks per round

City plan checkers issue correction letters when plans have errors, omissions, or code compliance issues. Each round adds 2–4 weeks. Most well-prepared submissions get through in 1–2 rounds. Poorly prepared plans — common with inexperienced designers — can require 3+ rounds, adding months.

Common delay
Homeowner decision delays
Adds 1–4 weeks per occurrence

Slow sign-offs on design revisions, late finish selections (tile, flooring, fixtures), and mid-construction change orders all push the schedule. Contractors can only move as fast as approvals come in. Pre-selecting finishes before construction begins eliminates most of this.

Site-specific delay
Unforeseen site conditions
Adds 1–6 weeks

Unexpected soil conditions, unmarked underground utilities, or structural issues in existing buildings discovered during demo can add time. A thorough pre-construction site assessment reduces but can't eliminate this risk entirely.

Less common
HOA design review
Adds 4–12 weeks

Communities with active HOAs (common in Carmel Valley, Scripps Ranch, Rancho Santa Fe) require architectural committee approval before or alongside city permits. HOA review timelines vary widely — some review monthly, some quarterly. Factor this in early if your neighborhood has an HOA.

Less common
Subcontractor availability
Adds 1–3 weeks

Trade labor in San Diego is tight. Electricians, plumbers, and framers often have queues. A well-organized general contractor pre-schedules trades ahead of need — gaps happen when subs are booked last-minute or coordination breaks down.

What your contractor handles vs. what you do

One of the biggest sources of timeline friction is unclear responsibility. Here's how it typically breaks down on an IL Total Design & Build project.

Task Who handles it Notes
Architectural drawings Contractor IL Total prepares all permit-ready drawings
Permit submission & corrections Contractor We handle all city correspondence and resubmittals
SDG&E service application Contractor Submitted as early as possible — we initiate this
Finish selections (tile, flooring, fixtures) Homeowner Pre-select before construction starts to avoid delays
Design review sign-offs Homeowner Fast feedback = faster drawings
HOA application (if applicable) Both We prepare the package; you submit as the property owner
School fees, water/sewer impact fees Homeowner Paid at permit issuance — your name, your check
Construction management & inspections Contractor We schedule and coordinate all city inspections
Tenant screening (post-CO) Homeowner You find the tenant; we can refer property managers
Above-garage ADU completed in San Diego by IL Total Design and Build
Above-garage ADU completed in San Diego · IL Total Design & Build

Know your timeline before you commit

We give every client a free feasibility assessment upfront — what your lot can build, what permits it needs, and a realistic project timeline based on your specific property and goals.

Book your free feasibility check →

Frequently asked questions

How long does it take to build an ADU in San Diego?
A typical detached ADU in San Diego takes 10–12 months from first consultation to certificate of occupancy. That includes 10–16 weeks for design and drawings, 60–90 days for city permitting, 3–5 months of construction, and 2–4 weeks for final inspections. Garage conversions can move faster (6–9 months). Two-story or coastal zone projects typically run longer (12–18 months). The single biggest wildcard is SDG&E's service connection backlog, which can add 6–12 weeks and cannot be expedited.
How long does ADU permitting take in San Diego?
California law requires the City of San Diego to approve or deny a compliant ADU application within 60 days of submission. In practice, well-prepared applications typically resolve in 60–90 days. Incomplete applications or those requiring multiple correction rounds can take 3–5 months. The City of San Diego also offers a pre-approved plan program under AB 1332 that can reduce permit time to approximately 30 days for eligible standard designs. Coastal Zone properties require an additional Coastal Development Permit, which typically adds 30–60 days.
What is the fastest way to build an ADU in San Diego?
The fastest path is a garage conversion or JADU (Junior ADU within the existing home). These skip foundation work, use existing structure, and often permit faster since the building envelope already exists. For new detached construction, submitting a complete, clean permit application on the first attempt saves 4–8 weeks versus a submission that comes back with correction rounds. Initiating the SDG&E service application concurrently with permit submission — rather than after permit issuance — is the single most effective way to prevent the most common delay.
Why is SDG&E causing delays on ADU projects?
If your ADU requires its own electrical meter and service connection — separate from the main home — San Diego Gas & Electric must process the application, design the service extension, and schedule their crew to install it. Their backlog currently runs 6–12 weeks from application to completed installation, and there is no expedite option available. This delay sits on the critical path to your Certificate of Occupancy because the city won't issue a CO until utility connections are complete and inspected. The mitigation: start the SDG&E process as early as possible, ideally when you submit your building permit, not after it's approved.
How long does ADU construction take in San Diego?
Active construction on a detached ADU typically runs 3–5 months from site mobilization to substantial completion. Smaller units (under 600 sq ft) on straightforward lots can come in closer to 3 months. Larger units, two-story designs, or projects requiring significant site work (grading, retaining walls) may run 5–7 months. Garage conversions often complete in 2–3 months of active construction since no foundation work is required. These timelines assume the permit is in hand and subcontractors are pre-scheduled — a well-organized general contractor pre-books trades rather than filling gaps reactively.
Does an HOA affect how long my ADU takes?
Yes — significantly, in some neighborhoods. HOAs cannot legally prevent you from building a state-compliant ADU, but they can require architectural committee review and approval of your design before or alongside city permitting. HOA review cycles vary: some boards meet monthly, some quarterly. In communities like Carmel Valley, Scripps Ranch, and Rancho Santa Fe, plan for 4–12 additional weeks if HOA approval is required. We prepare the HOA application package — but you submit it as the property owner, and the HOA's timeline is outside anyone's control.
Can I live in the ADU while my main home is being renovated, or vice versa?
Not until the Certificate of Occupancy is issued. The ADU is legally uninhabitable — and unrentable — until the city signs off on final inspections and issues the CO. Attempting to occupy or rent the unit before the CO creates legal liability and can complicate your final inspection. Plan your living arrangements around the CO date, which typically comes 2–4 weeks after construction is substantially complete.

Keep exploring

Disclosure: Timeline estimates in this article reflect typical IL Total Design & Build project experience in San Diego as of 2026 and are provided for planning purposes only. Actual timelines vary based on project complexity, city workload, HOA requirements, utility availability, and site conditions. Nothing in this article constitutes a contractual commitment to any specific timeline. Always verify current permit processing times with the relevant city or county planning department. IL Total Design & Build is a licensed general contractor (CSLB #1058676). Last updated May 2026.

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