ADUs in Downey: permits and local data
HCD records show 146 ADU units with building permits issued in Downey in 2025, as reported so far.
Downey at a glance
- ADU units with building permits issued in 2025 in Downey, as reported so far
- 146
- ADU units completed in 2025 in Downey, as reported so far
- 141
- Downey's rank by ADU units permitted in 2025 among 79 reporting Los Angeles County cities
- 9 of 79
California HCD, Housing Element Annual Progress Report (APR), Table A2 · data as of
- Numbers from HCD public records
- Up to three local contractors, never a long list
- Free, no obligation
What do permits say an ADU costs?
From City of LA building permits, last 12 months. Not a contract price. How we calculate this
Declared values on City of Los Angeles building permits, last 12 months. The dataset covers the City of Los Angeles only, so treat it as a regional reference for Downey. A declared value is what the permit states, not your contract price. How we calculate this.
Source: LA Department of Building and Safety, Building Permits Issued 2020 to Present (data.lacity.org), permits on one- and two-family homes issued to ; fire rebuilds excluded. ZIP medians need 20+ permits.
Downey ADU numbers from official state reports
Downey ADU numbers from official state reports
Local numbers for Downey, each with its source and date.
- Change in ADU units permitted in Downey, 2022 to 20251
- 6.6%
| Year | Count |
|---|---|
| 2019 | 16 |
| 2020 | 54 |
| 2021 | 127 |
| 2022 | 137 |
| 2023 | 142 |
| 2024 | 297 |
| 2025 | 146 |
9th of 79 LA County cities for ADU permits in 2025
* 2025 counts can still rise as late reports come in. Source: California HCD, Housing Element Annual Progress Report (APR), Table A2, data as of .
Planning your project
Downey is an active market for ADUs. State housing reports list 146 ADU units with building permits issued in 2025, as reported so far, and 141 ADU units completed that year. Downey ranks 9 of 79 reporting Los Angeles County cities for ADU units permitted in 2025.
Homeowners in Downey often build an ADU for rental income or to house family close by. The common types are detached backyard units, attached units built onto the main house, and garage conversions. Which type fits depends on your lot, your existing structures and the city's review.
The state data is a city total for Downey. It does not show prices or timelines for any one property, so ask a local builder to review your site before you plan the budget.
How an ADU gets built in Downey
How an ADU gets built in Downey
Check feasibility for your lot
Decide what you want the unit for, such as rental income or family housing. Check your lot size, existing structures and parking situation.
Prepare design and plans
Work with a designer or builder to draw the floor plan, site plan and structural details that the city needs for review.
Submit for plan check and permit
Submit the plans to the City of Downey. The city checks them against zoning and building codes and may ask for changes before it issues a permit.
Build with inspections
Build the unit under the issued permit. The city inspects key stages such as foundation, framing, utilities and insulation before work continues.
Get final sign-off and move in
After the final inspection and sign-off, the unit can be occupied. Keep the final approval paperwork with your property records.
ADU questions in Downey
Do I need a permit to build an ADU in Downey?
In most cases, yes. Adding an ADU usually means a building permit from the City of Downey. Whether your lot and plan qualify depends on zoning and the city's review, so confirm the details with the city and your builder before you start.
Can I convert my garage into an ADU in Downey?
Often, yes. A garage conversion is one of the common ADU types. Whether your garage can be converted depends on its size, setbacks, parking rules and utilities, and on the city's review. A local builder can look at your property and tell you what applies.
Can I rent out an ADU in Downey?
Many homeowners build an ADU to rent out or to house family. Check the city's rules on rentals and occupancy for your property before you plan around rental income.
How do I start planning an ADU in Downey?
Start by sketching how you want to use the space and checking your lot's basic limits. Then request a free, no-obligation estimate from a local builder who can review your site and explain the permit steps.
How many ADU permits does Downey issue?
The state report shows 146 ADU units with building permits issued in Downey in 2025, as reported so far. Late reports can still raise that count, so treat it as a current figure, not a final total.
Compare ADU activity across LA County
Where LA County is building ADUs
ADU units permitted in 2025, city by city. Select a city to open its guide.
- 0–21
- 22–28
- 29–56
- 57–99
- 100+
- No report
- Unincorporated
Most ADU permits in 2025
- 1Los Angeles7,446
- 2Long Beach644
- 3Glendale371
- 4Burbank241
- 5Pasadena222
- 6Lancaster209
- 7South Gate154
- 8Inglewood147
- 9Downey146
- 10Santa Monica143
Planning an ADU? A local builder can price yours.
Get my free estimatePermits: California HCD, Housing Element Annual Progress Report (APR), Table A2, data as of ; 2025 counts can still rise. Boundaries: Los Angeles County, City and Unincorporated Boundaries (Legal) (mainland only (islands omitted). simplified to about 300 m.)
Recent work by a contractor in our network
Photos from the contractor's own projects, used with permission. Captions name the type of work.
Bathroom in an ADU 
Addition / ADU interior 
Addition / ADU interior 
Addition / ADU bathroom
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Service areas
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- Brentwood
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Service areas as listed by the contractor ()