San Diego ADU Permit Data: How Many ADUs Actually Get Built? (2020 to 2026)

Source: City of San Diego permit records, ADU and JADU applications received 2021–2025. Project type is not a field the City reports; we classified each application ourselves by scanning the approval scope text for keywords (detached versus attached, new construction versus conversion or addition). See methodology section for details.

This report focuses on detached new construction. Conversions and additions range from a simple garage conversion to a complex addition, and that range distorts any comparison of time or completion. Detached new construction, built from the ground up, is the most consistent basis for measuring how long projects take and how many reach completion, so it is the cleanest lens on the submitted-to-built gap.

Applications received and permits granted, City of San Diego ADU/JADU permit activity by year.

Applications received climbed steadily from about 1,000 in 2020 to roughly 2,800 in 2025. These annual figures demonstrate the scale and growth of San Diego’s ADU activity. Because applications received and permits granted during a calendar year do not necessarily represent the same projects, the annual dashboard alone cannot show how many individual submissions advance. To answer that question, we followed projects through the underlying permit records over time.

Following detached new-construction ADUs from application to final inspection makes the drop-off concrete. Of those submitted at least three years ago, about three quarters were permitted within three years, but fewer than half were completed.

From application to finished ADU, detached new construction, City of San Diego. Based on projects submitted at least three years ago (distinct projects), measured at the three-year mark.

Following a submission cohort over time

To see the full picture, we followed every detached new-construction ADU from submission and measured, at successive time marks, the share that reached a permit and the share that reached completion. We did the same for SnapADU projects. This turns a static permit count into a completion curve that shows where and when projects drop out.

Detached new-construction ADUs, City of San Diego permit records, distinct projects. Solid lines show the share completed (reaching final inspection); dashed lines show the share permitted. SnapADU is a small sample of 43 projects (fewer at later marks); see methodology for how SnapADU projects are identified.

Among all detached new-construction projects in the dataset, 13% reached final inspection within 18 months, 24% within two years and 43% within three years. Among identifiable SnapADU projects, the corresponding completion rates were 52%, 69% and 90%.

Share of submitted projects reaching a permit, by time since submission

Share of submitted projects completed (final inspection), by time since submission

Detached new-construction ADUs, City of San Diego permit records, as a share of the original submission cohort (distinct projects). Each mark includes only projects old enough to have reached it, so the denominator is a different, smaller set at each mark.

By submission year

Completion rates vary by submission cohort, from 48% for identifiable 2021 submissions to 40% for 2022 and 37% for the portion of the 2023 cohort old enough to measure. These figures should not yet be interpreted as a definitive trend. Only the earliest 2023 submissions have accumulated three full years of history, and the 2021 extract has known data limitations. We therefore use the pooled cohort results for the core analysis.

A few forces are at work here. City permit timelines have lengthened. Enforcement of requirements such as fire access and brush management has tightened, both of which SnapADU has seen push projects later or off the table entirely. The other is a measurement effect: only the earliest 2023 submissions have had a full three years yet, so the 2023 figure rests on a partial slice and likely overstates the decline. The direction is consistent with what builders are seeing on the ground, but the most recent year should be read with that caveat.

Share of detached new-construction ADUs completed within two and three years, by submission year, City of San Diego (distinct projects). 2024 and 2025 cohorts are not yet old enough to evaluate at the longer marks; the 2023 three-year figure covers only its earliest submissions.

Submission-to-final-inspection durations computed from the permit data, by ADU type, with SnapADU’s detached new-construction average for comparison.

What the clock does not include

These durations measure from permit submission to final inspection. They do not include the design and feasibility work that comes before a permit application is filed. That earlier stage can take anywhere from about 6 weeks to 6 months or more, depending on the complexity of the project, whether a pre-approved plan is used, and how much utility mapping and feasibility work is done up front.

This is where preparation changes the timeline. SnapADU’s fastest pre-submission turnaround is now just under 3 months for a standard plan, including full utility mapping, utility planning, and surveys. Addressing these issues early can reduce avoidable design revisions and resubmittals once plan review begins.

Gathering more complete information from the start can improve predictably through every phase.

From Permit Approval to Completed Housing

The gap does not close once a permit is issued. To see what happens after approval, we looked at detached new-construction ADUs that had held a permit for at least three years, long enough that any of them could reasonably have been finished. About 76% had reached final inspection. The other 24% had not: roughly one in ten were cancelled or withdrawn after the permit was issued, about one in ten still had a permit on file with no construction recorded, and a small share were still under construction. Among the projects that did finish, the average time from permit to final inspection was about 16 months.

This is not necessarily a shortcoming of the permitting process. A permit is a critical milestone, and the City’s permit counts are an accurate record of approvals. Completion is simply a different and complementary measure, and the distance between the two reflects what tends to happen on the owner’s side after approval: budgets that come in higher than expected, financing that does not come together, site conditions that surprise, or limited builder capacity. For a homeowner, the practical takeaway is that reaching a permit, while a major step, is not the same as reaching a finished home, and preparing for the build phase matters as much as getting through plan check.

Where ADU Projects Can Lose Momentum

The City data shows whether a project moved from submission to permit to final inspection. It does not always show why a project stalled. In our experience, the most common breakdowns happen in five places:

1. Feasibility was not fully understood before design started
2. Utility scope was discovered too late, including electrical, water and sewer upgrades
3. Fire considerations were not taken into account
4. Plan check corrections required design changes instead of clarifications.
5. Financing did not line up after permit issuance.

This is why SnapADU puts so much weight on feasibility, utility mapping, scope definition, and realistic pricing before a client is deep into design.

What This Means

For homeowners

The most useful thing a homeowner can do before committing is to get an honest picture of feasibility and budget. The projects that finish are the ones where what is buildable on the lot, what it will actually cost, and who is carrying the work are all settled before design is locked. A permit in hand is a milestone, not a guarantee of a finished home.

For policymakers

San Diego’s high level of ADU activity creates an opportunity to study the full housing-delivery pipeline. Tracking applications, permit issuance, construction activity and final inspections together could help cities and industry partners distinguish challenges arising during design and plan review from those emerging during financing and construction.

That fuller view could support clearer applicant guidance, better-prepared submissions, more targeted homeowner resources and, ultimately, more completed homes. Cities, designers, builders, lenders and homeowners each influence whether an ADU advances from an initial application to occupied housing.

Methodology: About the Data

This report analyzes ADU and JADU permit activity for the City of San Diego, drawing on the City’s public permit data from the Development Services Department Open Data Portal. The data was last updated for this report in June 2026. We worked with the Development Services Business Intelligence team to confirm how the City’s published dashboard is constructed. SnapADU projects were identified within the same City dataset.

Counting projects versus permits

The City’s published dashboard counts permits (approval records), not projects, because a single project can carry more than one permit. We follow the City’s permit-level counts for the year-by-year applications-received and permits-granted figures, so those match the City’s published totals. For the completion analysis, we instead count distinct projects. A project that was cancelled and resubmitted, or that carries multiple permits, would otherwise be counted more than once, which over-counts cancellations and understates completion. Counting distinct projects gives a truer project-level completion rate. As a result, the project counts in the completion section are lower than the City’s permit-level published totals by design.

Identifying ADU and JADU projects

A permit is treated as an ADU or JADU if any of three signals is present: a recorded ADU or JADU unit total greater than zero; a job code the City classifies as an ADU (for example, Add/Alt Companion Unit/Acc Apt); or an ADU or JADU project tag (Companion Unit and Junior Unit variants, where Companion Units are ADUs and Junior Units are JADUs). Tags are joined on project_id, and records are filtered to the Building Permit and Combination Building Permit approval types.

Classifying detached new construction

ADU type is classified by scanning the approval scope text for keywords for detached, attached, new, conversion, remodel, and addition, then combined into two labels, detached versus attached and new versus conversion. Detached new construction is the set flagged as both detached and new. This text-based approach is practical at scale but approximate, since scope wording is hand-entered and varies.

Identifying SnapADU projects

SnapADU projects are identified two ways: by matching the recorded permit holder to SnapADU, and by matching SnapADU’s own project list to the City records by address. Because an ADU is usually addressed a few digits off the main home, addresses are matched on the street with a tolerance of several house numbers, which captures SnapADU projects still in plan check that a permit-holder match alone would miss. The resulting sample is small, 43 detached new-construction projects and fewer at the later time marks, so SnapADU figures are a directional comparison rather than a precise rate.

Status, milestones, and completion

Each permit’s status maps to one of five stages: Plan Check, Permit Issued, Construction in Process, Build Completed, and Cancelled or Withdrawn. A project is counted as completed only when it reaches Build Completed (final inspection), not when construction is merely underway. Four milestone dates drive the timeline: project create (the submission point), approval create, approval issue (permitted), and approval close (final inspection). Total time from submission to final inspection is the headline duration. Permitting time is counted only when at least 10 days, and build time only when at least 60 days, to drop administrative same-day records.

The completion curve follows a submission cohort over time. At the 6, 12, 18, 24, and 36 month marks after submission, each project is classified by the furthest milestone it had reached by that point. Only projects old enough to have reached a given mark are included at that mark. The headline that 57% were not completed within three years pools every detached new-construction project submitted early enough to have had three full years (2021 through early 2023, as of the June 2026 data).

Units and known limitations

• Unit counts. Recorded ADU unit counts are incomplete (no unit count is recorded for roughly 40% of detached-new permits), so they were not used to filter. Projects with three or more units are rare (under 3% where recorded), so multi-unit projects do not materially affect the results.
• Keyword classification. Type classification relies on hand-entered scope text, so a small share of records may be misclassified.
• SnapADU sample size. The SnapADU sample is small (43 projects, fewer at later marks), so SnapADU percentages are directional rather than precise.
• Observation window. Completion within three years can only be evaluated for cohorts at least three years old (2021 through early 2023).
• 2021 completeness. For 2021, records in the extract appear to begin in late July, while the dashboard reports roughly 1,500 applications; the City attributes most of this to project_id normalization. Early-2021 figures should be treated as provisional.

We are grateful to the City of San Diego Development Services Business Intelligence team for their help confirming how the permit data is structured and counted.

Questions About Your ADU Project?

SnapADU is a detached ADU design-build firm serving greater San Diego, handling feasibility, design, permitting, and construction under one roof. If you want a clear read on what is feasible on your property and what it would cost, you can contact our team for help.