In short
- 445 ADU permits since 2018.
- 80 in 2025, down 5% from 2024.
- Typical permit time: 209 days from application to permit (median of 391 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 | 10 | — | — |
| 2019 | 25 | — | — |
| 2020 | 20 | — | — |
| 2021 | 56 | — | — |
| 2022 | 77 | 0 | 0 |
| 2023 | 93 | 0 | 0 |
| 2024 | 84 | 0 | 0 |
| 2025 | 80 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 153 approved projects with no building permit reported yet.
ADU rules in Whittier
State law check: No HCD review letter on file (that isn't a finding either way). Its junior-ADU owner rule has no exception for a junior ADU with its own bathroom, stricter than current state law.
| Rule | Whittier's code | State law guarantees |
|---|---|---|
| Maximum size | Detached: 1,200 sq ft (1,500 sq ft on lots of 20,000 sq ft or more). Attached: 850 sq ft (0–1 bedroom) or 1,000 sq ft (2+), or 50% of the existing house if greater. 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 | One level as a rule. Detached: 16 ft (18 ft near transit, plus 2 ft for roof pitch; 18 ft beside a multistory apartment building). Attached: 25 ft or the zone limit; 2 stories if the house is. | 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 and street-side setbacks apply unless they'd block an 800 sq ft ADU. 5 ft from the house. None for conversions. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space (tandem on the driveway is fine) unless exempt (transit, historic district, inside existing space, car share, built with a new home); none for junior ADUs; no replacement parking. | 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, with a deed restriction. | 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 detached ADU, one attached 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 | 31 days or more, 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. |
- New ADUs aren't allowed in areas the city maps as having insufficient water or sewer service.
- Historic landmarks and districts: ADUs must meet the city's historic-resources rules (Ch. 18.84).
- Free pre-approved one-story detached plans (311 to 800 sq ft, three styles) get a 30-day review.
Where local rules conflict with state law, state law controls. Sources: Whittier Municipal Code § 18.10.020(I) (Ord. 3167, Sep 23, 2025); HCD's list of review letters; California ADU rules. Verified Sep 30, 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) | 126 | 100 – 309 | 12 |
| Unclassified | 210 | 134 – 355 | 379 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: How long ADU permits take in Los Angeles (and other cities) · How long ADUs take to build
From permit to completion
Of the 243 ADU permits Whittier reported issuing from 2020 through 2023, 175 (72%) have a completion reported to the state. For those, the median time from permit to completion was 9 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 Whittier? Feature your business on this page.
Questions about ADUs in Whittier
How many ADUs have been permitted in Whittier?
Public records show 445 ADU permits in Whittier from 2018 through 2025. 80 in 2025, down 5% 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 Whittier?
Among the 391 ADU permits in Whittier with both dates recorded, half were issued within 209 days of the application; the middle half took 132 to 353 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Whittier?
California law allows ADUs on most lots with a house, including in Whittier, 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 Whittier?
Apply with the City of Whittier's Community Development Department through the city's Online Permit Portal; the city offers free pre-approved detached ADU plans from 311 to 800 sq ft. 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.