In short
- 96 ADU permits on record, nearly all since 2019.
- 29 in 2025.
- Typical permit time: 54 days from application to permit (median of 20 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 | 2 | — | — |
| 2019 | 3 | — | — |
| 2020 | 6 | — | — |
| 2021 | 16 | — | — |
| 2022 | 13 | — | — |
| 2023 | 13 | — | — |
| 2024 | 14 | — | — |
| 2025 | 29 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
ADU rules in Lake Forest
State law check: No open HCD letter. HCD's last letter (October 17, 2022) closed its review of the 2022 ordinance; it hasn't reviewed the amendments since (latest January 2026). That is not a finding of compliance.
| Rule | Lake Forest's code | State law guarantees |
|---|---|---|
| Maximum size | Locally regulated ADU: 850 sq ft (studio or 1 bedroom) or 1,000 sq ft (2+ bedrooms); attached ADUs 50% of the house, but at least 800 sq ft. State-law detached ADU: 800 sq ft. 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 | Detached: 16 ft (18 ft near transit, plus 2 ft for roof pitch; 18 ft with a multistory apartment building). Attached: 25 ft or the zone limit, 2 stories. | 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; 25 ft front for locally regulated ADUs (can't block an 800 sq ft ADU). None for rebuilds in the same footprint. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space per ADU or per bedroom, whichever is less, unless exempt; none for state-law ADUs; no replacement parking. The ADU shares the house's driveway. | 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 on site unless it has its own bathroom; 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 | A converted ADU and a junior ADU, plus one new detached ADU up to 800 sq ft. | 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 | 30 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. |
- No ADUs or junior ADUs on lots created by an SB 684 small-lot subdivision.
- ADUs that don't meet the standards can seek a use permit.
- Every ADU and junior ADU gets its own address, applied for before the building permit.
Where local rules conflict with state law, state law controls. Sources: Lake Forest Municipal Code 9.146.050 · City ADU FAQ (2026) · HCD letter (October 17, 2022); 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 |
|---|---|---|---|
| Unclassified | 54 | 24 – 151 | 20 |
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 43 ADU permits Lake Forest reported issuing from 2020 through 2023, 35 (81%) have a completion reported to the state. For those, the median time from permit to completion was 11 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 Lake Forest? Feature your business on this page.
Questions about ADUs in Lake Forest
How many ADUs have been permitted in Lake Forest?
Public records show 96 ADU permits in Lake Forest through 2025, nearly all since 2019. 29 in 2025. 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 Lake Forest?
Among the 20 ADU permits in Lake Forest with both dates recorded, half were issued within 54 days of the application; the middle half took 24 to 151 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Lake Forest?
California law allows ADUs on most lots with a house, including in Lake Forest, 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 Lake Forest?
Apply with the City of Lake Forest's Community Development Department: an ADU permit (not needed for a conversion inside the house) and a building permit, through the eLakeForest portal. 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.