California law now allows ADUs on multifamily properties, not just single-family lots: owners of apartment buildings can convert unused interior spaces like storage rooms and boiler rooms into multiple ADUs, and add up to two detached ADUs on the lot. This has opened a major opportunity for multifamily owners. Here’s how the multifamily ADU rules work.
[updated February 2025]
ADUs have been a big topic of discussion due to the new laws recently passed, both at the California state level and put into effect in Los Angeles and other local city ordinances. I have written quite a few ADU articles about how these new guidelines will affect single-family properties in LA. The city has started to make the rules reasonably clear regarding Accessory Dwelling Units and garage conversions on single-family properties.
I don’t think the same can be said for multifamily properties, where there is still lots of confusion. So, let’s discuss what we know about ADUs (ADU definition) and garage conversions for multifamily properties.
Here at GreatBuildz, a free service that connects property owners with reliable general contractors, we get inquiries all the time about ADU guidelines from multifamily property owners – read below to learn more about the current ADU guidelines in Los Angeles, Orange County, Ventura or San Diego.
I recently went to the City of LA Building & Safety department and spoke to one of their staff members in the Zoning section. According to this staff person, all multifamily & apartment zoned properties are generally allowed to build an ADU or even multiple ADUs according to their ordinance.
New Multifamily ADU Laws for 2025:
SB 1211
Starting in 2025, SB 1211 shakes up the ADU rules for multi-family property owners. Right now, most multi-family properties can have up to two detached ADUs, but SB 1211 bumps that limit up to eight, as long as the number of ADUs doesn’t exceed the current number of units on the property.
This law makes it easier for property owners to maximize their space if they have room to add more units. It also relaxes parking rules, allowing ADUs to be built on existing parking spaces (covered or uncovered) without requiring those spots to be replaced.
Another perk of SB 1211 is that it limits local governments from imposing tough development or design rules on ADU construction. Plus, it defines “habitable space” as areas meant for living, like bedrooms, living rooms, and bathrooms.
Read SB 1211: https://legiscan.com/CA/text/SB1211/id/2986472
Restriction of ADU’s Based on Property’s Zoning
However, with multifamily properties, the city will be restricting the construction of Accessory Dwelling Units based on overlays specific to the property’s zoning. For example, each zoning has a maximum number of total units allowed based on the lot size; and maximum FAR (floor-area-ratio) or RFA (residential floor area). This means if your existing number of units already maximize what is allowed on your lot, you may be prohibited from constructing an ADU. Check out your property’s zoning and other restrictions at the City’s Zimas website.
Multifamily Property owners may be curious about the new senate bill 9 that was recently passed and whether it pertains to their property. According to the this link with Q/A about SB9 from the city of LA, SB9 is only applicable to single-family zoned properties. It goes on to say multifamily zoned properties can add units via the ADU ordinance or Small Lot subdivision ordinance or AB803. You can find more info on this at our latest SB9 blog.
Number of Multifamily ADUs is Limited
Another guideline in the city code worth discussing is the number of ADUs the city is allowing for multifamily properties. According to the staff person I spoke with, a multifamily property is limited to adding up to 25% of the existing number of units on site. So, for a duplex, triplex, or fourplex, one ADU would be allowed. While if you had 8 units, you could, in theory, add 2 ADUs. Again, this number will still be limited by the other overlays and guidelines that pertain to your property’s zoning. Read more about maximizing the units on your property in this memorandum from the City of LA.
Parking Regulations
Los Angeles Building and Safety staff are also currently advising that the parking requirements for construction of an ADU on multifamily properties mirror those for single-family homes. Specifically, parking is not being required for an Accessory Dwelling Unit as long as the property is within ½ mile from a transit stop (bus stops included).
From my conversation at the city, I sense that these ADU guidelines & regulations are still in flux and it may still take some time before they are as clear for multifamily and duplex/triplex/fourplex properties as they are for single-family. However, if you are a multifamily property owner and considering building an ADU (or several), I think it’s worth pursuing this opportunity. These approvals will be handled administratively through Building & Safety plancheck and won’t require discretionary planning department approvals (assuming you meet all zoning guidelines). The best first step is to find an architect who has some experience with multifamily ADUs and speak to them to verify your property will qualify for building an ADU. GreatBuildz can recommend a few designers well versed in this topic.
You can also start by doing some homework yourself. Although you can seek advice online, you really need to get a concrete answer from someone at the city. You can call 311 and speak to their Zoning staff to get most of the information you need. Even better, you should go in person to one of the city’s Building and Safety offices and speak to their zoning division. (The building department is only open by appointment since COVID)
Los Angeles ADU Regulations
Please be aware that these ADU and garage conversion guidelines are still relatively new to the city’s staff, so there is still quite a bit of confusion about what’s allowed and what’s not. Because the city staff is still trying to ‘interpret’ what State and City laws and ordinances really mean in the real world, you are likely to get different opinions from different city staff. Try to be patient and understand that these ADU rules are still ‘a moving target’. My advice is to speak with several city staff people and ideally a supervisor, until you get consistent advice. If you’re getting conflicting advice, keep working up the chain of command until you talk to someone with authority.
In some cases, a city’s guidelines/regulations won’t jive with the new California state ADU laws. If you feel like this is the case for your situation, there are ADU consultants and attorneys that can help in these situations. Feel free to contact GreatBuildz for some referrals to these types of professionals.
The State of California’s laws should prevail in most cases, so you’ll want to start by understanding the latest 2023 legislation that CA has put into effect – AB 221, AB 916, AB 561, and SB 897.
Another option is to find and hire a local Los Angeles architect who is well-versed and experienced with multifamily ADU regulations in the city. That person can help guide you through the laws and limitations of your property. The staff at GreatBuildz and recommend a few architects who are experienced with this space as well as ADU contractors who can also be helpful in providing estimated costs for your proposed multifamily ADU project.
If you have more questions about the ADU process or how to pick the right contractor for the project, we can help.
Frequently Asked Questions
Can you build an ADU on a multifamily property in California?
Yes. State law allows ADUs on multifamily properties. Owners can convert unused non-livable spaces, like storage areas, boiler rooms, or hallways, into ADUs (at least one, up to 25 percent of the existing units), and separately add up to two detached ADUs on the lot.
How many ADUs can a multifamily property have?
A multifamily property can convert unused interior spaces into ADUs equal to at least one unit or up to 25 percent of the existing units, and can also add up to two detached ADUs. The exact number depends on the building’s size and configuration.
Are multifamily ADUs a good investment?
For many apartment owners, yes. Converting unused space or adding detached units creates new rental income on land you already own, often at a lower cost per unit than new construction. Running the numbers with a contractor and checking local rules is the best first step.
GreatBuildz is a free service that connects homeowners in Los Angeles, Orange County, Ventura or San Diego with reliable, thoroughly screened general contractors and provides project support from start to finish.
You can call our friendly staff to be connected to several fully vetted, trustworthy contractors who are experienced with ADUs. For more info, visit www.GreatBuildz.com or call 818.317.3567 today.
