In short
- 531 ADU permits since 2018.
- 83 in 2025, down 27% from 2024.
- Typical permit time: 203 days from application to permit (median of 441 permits with both dates recorded).
About this data
- Source: California HCD Housing Element Annual Progress Reports. The state data does not say whether an ADU is detached, attached, a garage conversion or a JADU, so most records show as 'unknown'. Permit valuations are not published in this source. Timelines use the application date the city reported to the state, matched to the permit where possible; some cities report their planning application date, so timelines can include planning review. Each project is counted once, in its building-permit year (or completion year when no permit date was reported).
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 23 | — | — |
| 2019 | 36 | — | — |
| 2020 | 48 | — | — |
| 2021 | 66 | — | — |
| 2022 | 62 | 0 | 0 |
| 2023 | 100 | 0 | 0 |
| 2024 | 113 | — | — |
| 2025 | 83 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 4 approved projects with no building permit reported yet.
ADU rules in La Mesa
State law check: HCD sent a technical-assistance letter (May 11, 2026) noting the city's ordinance on file is from 2023 and may be outdated; no formal findings.
| Rule | La Mesa's code | State law guarantees |
|---|---|---|
| Maximum size | 1,200 sq ft, attached or detached; the city's matrix limits attached ADUs to 50% of the house. An 800 sq ft ADU is always allowed. Junior ADU 500 sq ft. | At least 850 sq ft (1,000 sq ft with 2+ bedrooms) must be allowed; an 800 sq ft detached ADU always is. Conversions of existing space have no size cap. Junior ADU: up to 500 sq ft. |
| Height | 20 ft in single-family zones, measured to the top of the wall plate (city ADU matrix). Multi-family zones: 20 ft in R2, 30 ft in R3 and RB. | Detached: at least 16 ft (18 ft within ½ mile of transit, plus 2 ft for a matching roof). Attached: 25 ft or the zone's limit, whichever is lower. |
| Setbacks | 4 ft side and rear; front setback per the zone, but it can't block an 800 sq ft ADU. Conversions keep the existing setbacks. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | None required for ADUs, and no replacement when a garage or carport is removed or converted. | At most 1 space; none within ½ mile of transit and in several other cases. No replacement parking when a garage is converted. |
| Owner living on site | None for ADUs. Junior ADU: the owner lives in the house or the junior ADU (the city's matrix says only when they share sanitation), with a recorded covenant. | None for ADUs. A junior ADU that shares a bathroom with the house requires the owner to live in one of them. |
| How many on a single-family lot | One attached ADU, one detached ADU and one junior ADU on a single-family lot. | One ADU converted from existing space, one junior ADU and one new detached ADU (up to 800 sq ft). From January 1, 2027: two new detached ADUs (a city then needn't allow a junior ADU on that lot). |
| Short-term rentals | More than 30 days, for ADUs and junior ADUs. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- The city offers pre-approved ADU plans from 224 to 1,199 sq ft; email Planning for the permit set.
- Lots of 10,000 sq ft or less with a house get 5% extra lot coverage for an ADU.
- Scenic Preservation and Hillside overlay rules still apply, but without a Planning Commission hearing. On historic sites, detached ADUs go behind the house.
- No impact fees under 750 sq ft. Fire sprinklers are required if the house has them or the back of the ADU is 150 ft or more from the curb.
Where local rules conflict with state law, state law controls. Sources: La Mesa Municipal Code 24.05.020 D.8-9 (amended March 14, 2023) · City of La Mesa ADU and JADU Development Matrix · HCD letter (May 11, 2026); HCD's list of review letters; California ADU rules. Verified Oct 5, 2026. Rules change and every lot is different: confirm with the city before you design.
How long permits take
| Type | Median days, application to permit | Middle half | Permits |
|---|---|---|---|
| Junior ADU (JADU) | 318 | 216 – 402 | 14 |
| Unclassified | 201 | 134 – 329 | 427 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: How long ADUs take to build
From permit to completion
Of the 272 ADU permits La Mesa reported issuing from 2020 through 2023, 170 (62%) have a completion reported to the state. For those, the median time from permit to completion was 10 months.
The state reports don't record expired or cancelled permits, and a completion the city hasn't reported looks the same as an unfinished project, so the share is a floor. Years with incomplete reports are left out.
What neighbors declared as cost
Cost data (declared permit valuations) is not published for this area in these sources.
Read more: How to choose an ADU builder
An ADU builder serving La Mesa? Feature your business on this page.
Questions about ADUs in La Mesa
How many ADUs have been permitted in La Mesa?
Public records show 531 ADU permits in La Mesa from 2018 through 2025. 83 in 2025, down 27% from 2024. These counts come from the city's reports to the state, which place a project in its completion year when no permit date was reported.
How long does an ADU permit take in La Mesa?
Among the 441 ADU permits in La Mesa with both dates recorded, half were issued within 203 days of the application; the middle half took 139 to 330 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in La Mesa?
California law allows ADUs on most lots with a house, including in La Mesa, but what you can build depends on your lot, local rules and utilities. This site shows permits, not eligibility. See California ADU rules.
Where do I apply for an ADU permit in La Mesa?
Apply with the City of La Mesa's Planning division through the MaintStar permit portal; the city also offers pre-approved ADU plans. Official ADU page.
How current is this?
- State annual progress reports: through 2025 (published once a year)
How our data works · Download the data · Free to reuse with credit to SoCal ADU Tracker (socaladutracker.com), under CC BY 4.0.