Statistics
ADU construction time statistics
34 of 47 figures are HyreADU calculations. Permit issuance to certificate of occupancy, estimated so that the 14,306 permits which have not finished stay inside the calculation instead of being quietly dropped.
Written by HyreADU Research Desk Primary-source research and data analysis
Audited by HyreADU Research Desk Provenance and figure-ledger audit
The short version
On 39,278 non-supplemental City of Los Angeles building permits that add an accessory dwelling unit, the estimated median time from permit issuance to certificate of occupancy is 499 days — about 16.4 months — with an interquartile range of 292–1066 days.
That figure keeps the unfinished permits in it, and that is the whole point. 14,306 of the 39,278 permits in the frame have no completion event yet.
Take the median of the 24,972 that finished and you get 367 days — 132 days shorter, roughly four months.
The shorter number is the one a builder’s own records would produce, and it is wrong in a specific direction: it can only see the projects that ended.
Only 35.3% of issued ADU permits reach a certificate of occupancy within a year, 65.1% within two and 75.5% within three.
What you build changes the clock more than anything else observable. A detached new build runs a median 564 days; an attached addition 528 days; a conversion coded as an alteration 419 days.
A junior ADU — a unit made inside an existing bedroom footprint — is fastest at 387 days.
And a substantial minority never finish on paper at all. 15.3% of the ADU permits Los Angeles issued in 2020 still have no certificate and no permit final, 6.2 years on; for the 2022 cohort it is 21.0%.
A statewide instrument agrees on the shape. Across California, among 81,853 matched projects HCD’s median permit-to-certificate lag is 1 year, with 78.9% inside one year and 93.9% inside two — and the 2018 permit cohort’s observed completion rate is 47.1% after seven years.
This is Los Angeles, not California and not the United States. It is not a compliance finding, not a construction schedule and not advice. 34 of 47 figures below are HyreADU calculations (34 hyreadu calculation, 12 agency published, 1 trade / survey estimate).
Read this before you use the number
Five constraints. The first is a statistical point that changes the headline by four months, so it is not optional.
- Unfinished permits have to stay in the calculation
14,306 of 39,278 permits in this frame have not reached a certificate. Dropping them and taking the median of the 24,972 that finished gives 367 days instead of 499 days.
That is not a rounding difference; it is a systematic bias, because the projects that take longest are precisely the ones most likely to be unfinished on the day you look.
Every headline figure here is a Kaplan-Meier product-limit estimate, which keeps a permit in the denominator until the day it drops out of observation. The completed-only figure is printed beside it every time.
- This is one city, and it is not California
Los Angeles is the only jurisdiction this desk has found that publishes an issuance date and a certificate-of-occupancy date on the same permit row.
San Francisco, Sacramento, San José, unincorporated Marin and San Diego were all opened; none of their published extracts carries a usable completion date paired to an ADU flag. So the frame is the City of Los Angeles.
A statewide instrument is set alongside it below, at much coarser resolution.
- A certificate is a paperwork event, not a move-in date
The clock stops when the department records a certificate of occupancy (24,876 cases) or a permit final (96).
Some units are occupied before that record exists and some sit finished for months while a last inspection is chased.
Equally, a permit with no final is not necessarily an empty building site — it can be a finished ADU whose owner never closed the permit out.
- This clock starts at issuance, not at the beginning of the project
Everything before the permit — design, plan check, corrections, fees — is the other clock, and in Los Angeles its median is 162 days.
Adding the two medians gives 661 days, about 1.8 years, and that sum is a HyreADU cross-study calculation offered as an order of magnitude. It is not a measured end-to-end duration on the same permits.
- None of this is a schedule for your project
The interquartile range here is wider than the median. That means the middle half of ADU projects in one city have experiences that differ by more than two years. Use these figures to sanity-check a timeline someone has given you, not to build one. HyreADU does not design, permit or build accessory dwelling units.
Why the honest number is four months longer than the builder number
Imagine standing in the middle of a marathon course with a stopwatch and recording the finishing times of everyone who has already crossed the line.
Your average will be excellent, and it will be wrong, because the runners still on the course are exactly the slow ones.
That is what happens to every ADU build-time figure computed from completed projects.
In this frame the effect is large and measurable. Across all 39,278 permits, the censored-aware median is 499 days.
Across only the 24,972 that finished, it is 367 days — 132 days, roughly four months, shorter.
The mean on finished permits is 446 days, which is closer but is a mean, and means on right-skewed distributions describe nobody.
The bias gets worse the more recent the cohort, which is visible in the chart above: the two lines are close for 2020-issued permits, where most projects have had time to finish either way, and far apart for 2025-issued permits, where the completed-only median of 258 days is a statement about the unusually fast minority that has already closed out. A trade figure sourced from recent projects is therefore doubly optimistic.
Kaplan-Meier is the standard tool for this and it is not exotic — it is the same estimator used for survival curves in medicine.
It keeps every permit in the denominator until the day it either completes or leaves observation, so a permit issued in 2025 contributes evidence about the first fourteen months and then stops contributing rather than being counted as either fast or infinite.
The full method, including the four sensitivity frames, is on the construction-duration study.
When permits actually finish
The median is one point on a curve, and for anyone planning around this the curve is more useful. These are the cumulative shares reaching a certificate of occupancy at four horizons.
| Horizon after permit issuance | Share reaching a certificate | Remaining | Class |
|---|---|---|---|
| Within 1 year | 35.3% | 64.7% | HyreADU calculation |
| Within 18 months | 54.3% | 45.7% | HyreADU calculation |
| Within 2 years | 65.1% | 34.9% | HyreADU calculation |
| Within 3 years | 75.5% | 24.5% | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05, observation window closing 2026-08-31. Kaplan-Meier product-limit estimates on n = 39,278 permits with 24,972 observed completion events.
Read the last row carefully. Roughly a quarter of issued Los Angeles ADU permits have not produced a certificate of occupancy three years after issuance. That is the number that should be in any risk conversation about an ADU project, and it is almost never the number in a brochure.
By what is actually being built
The permit type is the closest thing in this data to a construction method, and it moves the median by 145 days between the extremes — more than any other cut on this page.
A new-construction permit is a detached unit with a foundation, a new service and a full structural review. An alteration permit is usually a garage or interior conversion.
A junior ADU is a unit created inside an existing bedroom footprint, and it is the fastest thing in the dataset.
| What the permit describes | Median | IQR | Within 1 year | Within 2 years | n | Completed-only median | Class |
|---|---|---|---|---|---|---|---|
| New construction (detached ADU) | 564 days | 365–1058 days | 25.0% | 62.5% | 10,612 | 439 days | HyreADU calculation |
| Addition (attached ADU) | 528 days | 325–1121 days | 31.0% | 63.3% | 12,227 | 393 days | HyreADU calculation |
| Alteration/repair (conversion) | 419 days | 230–999 days | 44.6% | 68.2% | 16,438 | 304 days | HyreADU calculation |
| Junior ADU (JADU) | 387 days | 212–908 days | 47.3% | 70.3% | 3,778 | — | HyreADU calculation |
| Standard ADU | 509 days | 301–1086 days | 34.0% | 64.5% | 35,500 | — | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05. Kaplan-Meier medians; the last column shows what each row would look like if unfinished permits were dropped, which is between four and five months shorter in every case.
The ordering is intuitive and the size of the gap is not.
A conversion finishes 145 days sooner than a detached new build at the median, and 19.6% more of them are done inside a year.
See the garage-conversion page on what a garage conversion actually involves, and the junior-ADU page on why junior units behave differently from everything else here.
By the year the permit was issued
Each row is a permit cohort followed forward. Recent cohorts have had less time to complete, so their censored-aware medians are estimates over a shorter observation window and their completed-only medians are severely biased — both are printed so the difference is visible.
| Permit issue year | Issued | Completed so far | Censored-aware median | Completed-only median | Within 1 year | Class |
|---|---|---|---|---|---|---|
| 2020 | 3,373 | 2,856 | 486 days | 395 days | 39.1% | HyreADU calculation |
| 2021 | 5,071 | 4,174 | 508 days | 427 days | 33.0% | HyreADU calculation |
| 2022 | 7,120 | 5,625 | 536 days | 429 days | 31.6% | HyreADU calculation |
| 2023 | 6,158 | 4,674 | 512 days | 394 days | 34.2% | HyreADU calculation |
| 2024 | 6,394 | 4,384 | 476 days | 342 days | 37.7% | HyreADU calculation |
| 2025 | 6,933 | 3,045 | 462 days | 258 days | 37.9% | HyreADU calculation |
| 2026 | 4,229 | 214 | 0 days | 126 days | 16.4% | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05. 2026 is a part year. The completed-only column falls sharply in recent years for a reason that has nothing to do with faster building: in a young cohort, the only permits that have finished are the fast ones.
The censored-aware medians are broadly stable across cohorts — 486 days for 2020, 536 days for 2022, 476 days for 2024 — which is the more honest reading than the completed-only column’s apparent collapse from 395 days to 258 days.
The permits that never close out
Permits that never close out are the finding the study did not expect, and they are separate from the duration question. These four cohorts are mature enough that a normal project would have finished. A meaningful share of them has no certificate of occupancy and no permit final at all.
| Permit issue year | Issued | Completed | No final | Share with no final | Years elapsed | Class |
|---|---|---|---|---|---|---|
| 2020 | 3,373 | 2,856 | 517 | 15.3% | 6.2 | HyreADU calculation |
| 2021 | 5,071 | 4,174 | 897 | 17.7% | 5.2 | HyreADU calculation |
| 2022 | 7,120 | 5,625 | 1,495 | 21.0% | 4.2 | HyreADU calculation |
| 2023 | 6,158 | 4,674 | 1,484 | 24.1% | 3.2 | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05, observation window closing 2026-08-31. Years elapsed are measured from the midpoint of the issue year.
Of the 14,306 open permits across all years, 12,735 remain in "Issued" status, 701 are marked "CofO in Progress" and 304 have expired.
These are not all abandoned projects — some are finished units whose owners never closed the permit — but they are the permit-to-completion gap made visible at the level of the individual project, which is exactly what the statewide HCD figures cannot show.
The builder-attrition study looks at the builder side of the same gap.
By area of the city
Seven area planning commissions, one building department, one code. The spread between the fastest and slowest medians is 121 days — real, but much smaller than the spread by ADU type, which is the useful comparison to keep in mind.
| Area planning commission | Median | IQR | Within 1 year | Within 2 years | n | Class |
|---|---|---|---|---|---|---|
| South Valley | 464 days | 277–1014 days | 38.2% | 67.0% | 11,379 | HyreADU calculation |
| North Valley | 467 days | 273–975 days | 38.4% | 67.5% | 9,764 | HyreADU calculation |
| South Los Angeles | 551 days | 321–1258 days | 31.0% | 61.0% | 6,297 | HyreADU calculation |
| West Los Angeles | 504 days | 301–1001 days | 34.2% | 65.8% | 4,196 | HyreADU calculation |
| East Los Angeles | 527 days | 305–1070 days | 33.0% | 64.6% | 3,346 | HyreADU calculation |
| Central | 585 days | 334–1370 days | 28.7% | 59.0% | 3,274 | HyreADU calculation |
| Harbor | 529 days | 314–977 days | 32.3% | 65.2% | 1,022 | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05. The two San Fernando Valley commissions — South Valley and North Valley — carry 53.8% of the city’s ADU permits between them and are also the two fastest.
Do not read this as a map of departmental performance. Area correlates with lot size, lot slope, the age and construction type of the existing house, the prevalence of garage conversions, and the mix of owner-builder against contractor work. It is a description of where the slower projects are, not an explanation of why.
The statewide check: HCD’s permit-to-certificate lag
A second instrument, at coarser resolution, across all of California. HCD’s Table A2 records both a permit and a completion for a project, so a lag can be measured in whole calendar years across 81,853 matched projects statewide.
It cannot see days, and it can only see projects whose completion was reported under the same identifier — but it is not one city.
| Lag from permit year to completion year | Matched projects | Share | Class |
|---|---|---|---|
| Same calendar year | 24,077 | 29.4% | HyreADU calculation |
| One year later | 40,486 | 49.5% | HyreADU calculation |
| Two years later | 12,264 | 15.0% | HyreADU calculation |
| Three years or more | 4,974 | 6.1% | HyreADU calculation |
| Negative (reporting artefact) | 52 | 0.1% | HyreADU calculation |
HyreADU calculation on HCD APR Table A2, retrieved 2026-09-05. Median lag 1 year; 78.9% of matched projects complete within one year and 93.9% within two. 52 projects show a completion dated before the permit, which is a reporting artefact rather than a finding.
Two cautions. First, calendar-year lag is coarser than it sounds: a permit issued in December and a certificate issued the following February is a one-year lag here and ten weeks in reality.
Second, this table only contains projects that matched — statewide, 40.9% of 2018–2023 permit units have no matching completion row at all, and those are disproportionately the slow and the stalled. Both instruments therefore describe the finishing projects better than the stuck ones. See the permits-vs-completions study.
How the headline moves under different definitions of "an ADU permit"
One dataset, four defensible ways to decide which rows are ADU permits. The headline frame uses the department’s net-unit change and junior-ADU flag with supplementals excluded. The other three are printed so you can see that the finding does not depend on that choice.
| Frame | n | Completions observed | Median | IQR | Class |
|---|---|---|---|---|---|
| Headline: permit adds a net ADU or JADU (adu_changed > 0 or junior_adu = 1), supplementals excluded | 39,278 | 24,972 | 499 days | 292–1066 days | HyreADU calculation |
| Department use classification only (use_desc contains “Accessory Dwelling”), supplementals excluded — the ADU-04 classifier | 25,979 | 16,660 | 506 days | 301–1071 days | HyreADU calculation |
| Both classifiers must agree | 25,360 | 16,267 | 508 days | 304–1071 days | HyreADU calculation |
| Headline classifier, supplemental permits left in | 41,359 | 26,618 | 485 days | 280–1025 days | HyreADU calculation |
HyreADU calculation on LADBS pi9x-tg5x, retrieved 2026-09-05. The four frames span 485 to 508 days at the median — a range of 23 days, which is small next to the 132-day difference the censoring correction makes.
That comparison is the point of the table. Which rows you call ADU permits barely moves the answer. Whether you keep unfinished permits in the calculation moves it by four months.
Every figure on this page, with its class
47 figures with geography, date, provenance class and source. 34 HyreADU calculations, 12 agency-published, 1 trade or survey.
| Statistic | Figure | Geography | Date | Class | Source |
|---|---|---|---|---|---|
| Permit rows downloaded from the department feed | 409,619 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Rows carrying the department’s ADU or JADU flag | 41,374 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Supplemental permits excluded from the frame | 2,095 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Permits in the analysis frame | 39,278 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Permits with a completion event observed | 24,972 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Permits with no completion event observed | 14,306 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Completions recorded via a certificate of occupancy | 24,876 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Completions recorded via a permit final rather than a certificate | 96 | City of Los Angeles | 2020–2026 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Open permits still in “Issued” status | 12,735 | City of Los Angeles | as of 2026-08-31 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| Open permits marked expired | 304 | City of Los Angeles | as of 2026-08-31 | Agency published | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) |
| ADU certificates of occupancy reported statewide | 102,356 | California, 511 reporting jurisdictions | 2018–2025 | Agency published | HCD Housing Element APR, Table A2, retrieved 2026-09-05 |
| Matched permit-to-certificate project pairs statewide | 81,853 | California, 511 reporting jurisdictions | 2018–2025 | Agency published | HCD Housing Element APR, Table A2, retrieved 2026-09-05 |
| Median days, permit issuance to certificate of occupancy | 499 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Same median expressed in months | 16.4 months | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Interquartile range, issuance to certificate | 292–1066 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median computed on finished permits only | 367 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Understatement produced by ignoring unfinished permits | 132 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Mean on finished permits only, for contrast | 446 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Share reaching a certificate within one year | 35.3% | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Share reaching a certificate within eighteen months | 54.3% | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Share reaching a certificate within two years | 65.1% | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Share reaching a certificate within three years | 75.5% | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median, new construction (detached ADU) | 564 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median, addition (attached ADU) | 528 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median, alteration or repair (conversion) | 419 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Gap between a detached new build and a conversion | 145 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median, junior ADU | 387 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median, standard ADU | 509 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Share of junior ADUs finished within a year | 47.3% | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Slowest area planning commission by median | Central, 585 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Fastest area planning commission by median | South Valley, 464 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Spread between fastest and slowest area | 121 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| 2020-issued permits with no final | 15.3% (517 of 3,373) | City of Los Angeles | 2020 cohort | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| 2021-issued permits with no final | 17.7% | City of Los Angeles | 2021 cohort | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| 2022-issued permits with no final | 21.0% | City of Los Angeles | 2022 cohort | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| 2023-issued permits with no final | 24.1% | City of Los Angeles | 2023 cohort | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median under the department-classification sensitivity frame | 506 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median when both classifiers must agree | 508 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Median with supplemental permits left in | 485 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · construction-duration study |
| Statewide median permit-to-certificate lag among matched projects | 1 year | California, 511 reporting jurisdictions | 2018–2025 | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| Matched projects completing in the permit year | 29.4% | California, 511 reporting jurisdictions | 2018–2025 | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| Matched projects completing within one year | 78.9% | California, 511 reporting jurisdictions | 2018–2025 | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| Matched projects completing within two years | 93.9% | California, 511 reporting jurisdictions | 2018–2025 | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| Matched projects taking three years or more | 4,974 | California, 511 reporting jurisdictions | 2018–2025 | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| 2018 permit cohort, observed completion rate after seven years | 47.1% | California, 511 reporting jurisdictions | 2018 cohort | HyreADU calculation | HCD Housing Element APR, Table A2, retrieved 2026-09-05 · permits-vs-completions study |
| Combined median of both clocks, application to certificate | 661 days | City of Los Angeles | 2020–2026 | HyreADU calculation | LADBS resource pi9x-tg5x, retrieved 2026-09-05 (rowsUpdatedAt 2026-08-31, observation window closes 2026-08-31) · permit-times study + construction-duration study |
| New California ADUs that are one-bedroom | 61% | California, 2018–19 owner survey | Apr 2021 | Trade / survey estimate | Chapple, Ganetsos and Lopez, CCI, 22 April 2021 |
HyreADU calculation — computed by HyreADU, method on the construction-duration study. Agency published — a frame count printed by the department or by HCD. Trade / survey estimate — a named survey. LADBS extract retrieved 2026-09-05, observation window closing 2026-08-31.
Build-time claims we will not repeat
- “An ADU takes three to six months to build”
On 39,278 Los Angeles permits, 35.3% reach a certificate within a year.
Three to six months is not the median, not the first quartile (292 days is over nine months) and not a horizon at which any meaningful share of this distribution has finished.
The claim is roughly what you get from the completed-only median of 367 days with further optimism applied, and it survives because the people quoting it never see the permits that stalled.
- A national or statewide ADU build time
Exactly one jurisdiction in the country, as far as this desk can establish, publishes an issuance date and a completion date on the same ADU permit row.
Any figure presented as a national ADU construction time is either a trade estimate or an extrapolation from somewhere it was not measured.
HCD’s statewide lag is real but is measured in whole calendar years and only over matched projects.
- A build time computed from finished projects only
This is the single most common methodological error in the category and it is worth 132 days.
A builder reporting "our average ADU takes fourteen months" is reporting the truth about their finished jobs and saying nothing about the ones still open.
The correction is not a matter of opinion — it is the difference between 367 days and 499 days on the same permits.
- A permit-with-no-final read as an abandoned project
15.3% of 2020-issued permits have no final. That set includes genuinely stalled projects, and it also includes finished ADUs whose owners never chased the last inspection, projects re-permitted under a new number, and units sold mid-build.
We publish the share and name what it contains. Converting it into an abandonment rate would be a fabrication with a real number attached.
Citing these figures
Cite the construction-duration study rather than this digest where you can — the estimator, the four sensitivity frames and the completion-path definitions live there.
For anything labeled HyreADU calculation from the Los Angeles data, attribute it as "HyreADU analysis of City of Los Angeles building permits (Socrata pi9x-tg5x), retrieved 2026-09-05, Kaplan-Meier estimate".
For the statewide lag, attribute it as "HyreADU analysis of the California HCD Housing Element Annual Progress Report, Table A2". Corrections go on the page with a dated note: hello@hyreadu.com.
If you are quoting a single figure and have room for only one qualification, make it this one: 499 days, City of Los Angeles, censored-aware. Dropping either the city or the estimator turns a careful measurement into a misleading one.
Questions
How long does it take to build an ADU?
Why is your figure so much longer than what builders quote?
Does a garage conversion go faster than a detached new build?
What share of ADU projects finish within a year?
What happens to the permits that never get a certificate?
Is this a California figure or a national one?
How long is the whole process, from first application to keys?
Does where in the city you build change the build time?
Does the finding depend on how you defined an "ADU permit"?
How current is this and when will it change?
Written and audited by
HyreADU Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a builder. We read the permit extract, the statute, the HCD return or the fee schedule ourselves, and publish each figure with its source and retrieval date.
Where a number cannot be traced to a primary source, we leave it out and say what we could not verify. Our store-based claims cover California only.
- CA
- the only state this desk will make store-based claims about
- 5
- jurisdictions with extracted ADU permit evidence
- 735
- CSLB-verified companies in the California store
- 0
- national claims from a one-state store
How this desk works
- Primary sources only. Permit counts come from the city or county that issued the permit. Production counts come from HCD’s Annual Progress Report. Rents come from HUD or the Census. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- This is a California site. The company store is 734 California firms and one New Mexico firm. Permit evidence exists for five named jurisdictions: Los Angeles, San Francisco, Sacramento, San José and unincorporated Marin. A number from that store is titled to those places, never to the United States.
- A permit is not a completion, and a license is not an ADU grade. California licenses no ADU classification. Being named on an ADU permit is evidence of engagement in that jurisdiction, not of quality, completion, or work anywhere else. Owner-builder permits are excluded from contractor counts.
- Calculation is labeled as calculation. Figures we derive are never presented as something HCD, HUD, the Census or a city published. Terner Center research is cited as Terner’s, never restated as ours.
- We do not design, permit or build ADUs, and we take no payment for placement, ranking or a favorable mention. Pages that look like rankings are not: they publish public-record counts and let the reader decide.
- Nothing here is legal, tax or financial advice. Zoning, underwriting and appraisal practice vary by jurisdiction, lender and appraiser. The useful next step on a specific lot is the planning counter and a licensed professional.
Data as of LADBS resource pi9x-tg5x retrieved 2026-09-05; feed rowsUpdatedAt 2026-08-31; observation window closes 2026-08-31; HCD APR Table A2 retrieved 2026-09-05. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold.
Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
- LADBS — Building and Safety Building Permits Issued from 2020 to Present (Socrata pi9x-tg5x) , 409,619 rows downloaded. The only extract this desk has found that carries an ADU flag, an issue date and a certificate-of-occupancy date on the same row. 41,374 ADU-flagged rows, 39,278 in the analysis frame after excluding 2,095 supplementals. Retrieved 2026-09-05.
- California HCD — Housing Element Annual Progress Report, Table A2 , The statewide cross-check. 81,853 matched permit-to-certificate project pairs, median lag 1 calendar year, 78.9% within one year. Retrieved 2026-09-05.
- California HCD — Table A2 CSV download , The file itself, for reproduction of the statewide lag distribution. Retrieved 2026-09-05.
- Chapple, Ganetsos and Lopez — Center for Community Innovation ADU owner survey (Terner-reviewed) , Survey of 2018–19 California ADU owners; 61% of new units one-bedroom, 18% studios. Cited as theirs; used here only to characterize what kind of unit these permits describe. Retrieved 2026-09-05.
Half of these projects take longer than sixteen months
A quarter of these projects have no certificate of occupancy after three years. If a schedule you have been shown assumes six months, it is not describing this distribution.
HyreADU does not design, permit or build accessory dwelling units. These statistics are informational and are not construction, legal or financial advice, and they are not a schedule.
Every figure describes the City of Los Angeles unless explicitly labeled statewide; there is no national ADU construction-time series and nothing here is scaled into one.
A certificate of occupancy is a paperwork event, not a move-in date, and a permit with no final is not necessarily an abandoned project.
Headline durations are Kaplan-Meier estimates; the completed-only figures are printed beside them precisely because they are biased.