One of the most frequently asked questions APLA receives from Los Angeles property owners is: “Can I add an ADU to a duplex or apartment building?” The answer — as of 2026 — is a nuanced yes, thanks to California’s progressive ADU legislation. This guide explains the current rules for ADUs on multifamily properties in Los Angeles, the costs involved, and how SB 9 further expands your options.
California Government Code Section 65852.2 (as amended by AB 881, AB 3182, and AB 2221) allows ADUs on multifamily residential properties under specific rules:
On a multifamily property (duplex, triplex, apartment building), you may convert non-livable space (storage rooms, garages, common areas, carports, laundry rooms) into ADUs. You may convert as many as 25% of existing units or a minimum of 1 ADU — whichever is greater. These conversions do not require LADBS to impose parking replacement requirements.
On any multifamily residential lot, you may add at least 2 new detached ADUs, regardless of lot size or the number of existing units. This is a significant 2022 change (AB 2221) that substantially expanded ADU rights on multifamily properties.
Senate Bill 9 (effective 2022) allows ministerial lot splits on single-family zoned lots — splitting one parcel into two, each of which can then have a primary dwelling and an ADU. This allows up to 4 units on what was previously a single-family lot. Not available on multi-family-zoned properties directly, but significant for SFR owners considering multifamily conversion.
| ADU Type on Multifamily | Typical Cost |
|---|---|
| Converting non-livable space (storage, garage) on duplex | $75,000–$140,000 |
| New detached ADU on multifamily lot (studio/1BR) | $145,000–$195,000 |
| New detached ADU on multifamily lot (2BR) | $175,000–$225,000 |
| Converting a carport or covered parking to ADU | $60,000–$110,000 |
Adding ADUs to a multifamily property stacks rental income and increases property value through both mechanisms:
Under current California law: at minimum, 2 new detached ADUs on any multifamily lot, plus conversions of non-livable space (up to 25% of existing units or 1 minimum, whichever is more). A duplex owner in Los Angeles can potentially add 2–4 ADUs depending on the specific lot conditions and scope.
No. California law specifically prohibits cities from requiring parking replacement for ADU conversions of existing non-livable space (garages, carports, storage) on multifamily properties. New detached ADUs may have independent parking requirements depending on location (transit proximity, etc.).
ADU rights are limited to residentially zoned parcels. Mixed-use commercial-residential properties may qualify if the residential component meets the minimum criteria. APLA evaluates each property for ADU eligibility during the initial consultation.
Yes. APLA (CA Lic #1136359) builds ADUs on single-family homes, duplexes, and multifamily properties throughout Los Angeles. Call (818) 818-4419 for a free ADU feasibility analysis of your specific property.
Call: (818) 818-4419
Email: info@aplaconstruction.com
CA General Contractor License #1136359
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