Today, a California single-family lot can generally combine one converted ADU, one detached new-construction ADU, and one Junior ADU, for up to three units plus the main house. Starting January 1, 2027, AB 956 adds another path: up to two detached new-construction ADUs, though a city then isn’t required to also allow a JADU.
What your lot can actually hold depends on its size, utilities, and local rules.
What ADU types can you combine today?
| ADU type | What it is |
|---|---|
| Converted ADU | Created inside the existing home or an existing accessory structure, such as a garage |
| Detached new-construction ADU | A new backyard unit; a city may cap this path at 800 sq ft with 4-foot side and rear setbacks |
| Junior ADU | Up to 500 sq ft within the walls of the single-family home |
SB 543, effective in 2026, confirms these types can be combined on one lot. The City of Santa Clarita’s 2026 ADU handout also says you may have each type of ADU on your property.
What does that look like in practice?
Today: the three-unit combination. A garage conversion, a detached backyard ADU, and a JADU inside the house. That’s four homes on one lot, counting the main house.
From 2027: two detached ADUs. Under AB 956, two new detached ADUs, each of which a city may cap at 800 sq ft. A city isn’t required to approve a JADU on that lot too. How cities treat a converted ADU alongside two detached units may depend on local implementation, so ask before you plan it.
Multifamily lots: different rules. SB 1211, in effect since 2025, allows up to 8 detached ADUs on a lot with an existing multifamily building, capped at the number of existing units, plus ADUs converted from non-living space.
What limits how many units you can really build?
- Lot size and layout. Each unit needs room for setbacks, access, and separation. Sketch your lot before you assume.
- Utilities. Each added unit can mean a panel upgrade, sewer lateral work, or a larger water meter.
- Septic. In Acton and Agua Dulce, septic capacity is often the real limit. See ADUs on septic and well.
- Fire access. High fire hazard areas can bring access and fuel modification requirements.
- HOAs. State law limits HOA power to block ADUs, but reasonable design review still applies. See HOAs and ADUs.
How do rentals work with several units?
Each unit gets its own lease, and every ADU and JADU rental must be longer than 30 days. With two or three tenants, you’re running a small rental business. See renting out your ADU.
What should you do first?
- Get your lot dimensions and sketch what fits with setbacks.
- Check your electrical panel, sewer or septic, and water meter.
- Decide the goal: rental income, family housing, or both.
- Talk to a contractor who has built multi-unit ADU projects.
Want a contractor to look at your lot?
Call (661) 486-8393. If no one answers, leave a voicemail with your name, phone number, address, and the type of ADU you want. You can also use the contact form. We’ll pass your details to a local ADU contractor, who will follow up with you directly. There’s no obligation to hire.
ADUs per lot FAQs
Can I build an ADU and a Junior ADU on the same lot?
Yes. State law and the City of Santa Clarita allow a JADU alongside an ADU on a single-family lot.
Can I build two detached ADUs now?
Not under the AB 956 path until January 1, 2027. Today the guaranteed path covers one detached new-construction ADU.
Is there a minimum lot size for an ADU?
State law doesn’t allow cities to set a minimum lot size for ADUs. Your lot still has to physically fit the unit with required setbacks.
Do I need parking for each ADU?
The City of Santa Clarita’s handout says there are no parking requirements for ADUs or JADUs. In LA County areas, many ADUs are exempt from parking under state law, so check for your address.