California’s 2027 ADU Law Changes: What Los Angeles Homeowners Should Know
Two detached ADUs on one single-family lot, lower impact fees for larger ADUs and fewer plan-check rounds. Here’s what changes on January 1, 2027.
California keeps expanding what homeowners can build in their backyards. A new package of state laws signed in September 2026 takes effect on January 1, 2027. The biggest change for Los Angeles homeowners: on a lot with one single-family house, the city must now allow two detached, newly built accessory dwelling units (ADUs) instead of one.
Below is a plain-English summary of what changes, what stays the same, and what to check before you start planning. This is general information, not legal advice — rules are applied address by address, so always confirm with the city or a licensed professional.
1. Two detached ADUs on a single-family lot (AB 956)
Until now, state law required cities to approve one detached, new-construction ADU on a single-family lot through a ministerial (by-right) process. AB 956 doubles that to two. Cities can still apply a few standards to each detached ADU:
- a size cap of 800 sq ft per detached ADU,
- side and rear setbacks of up to 4 feet,
- the height limits already set in state ADU law.
On a qualifying single-family lot, the maximum combinations become: one converted ADU (inside the house or an existing structure) + one junior ADU (JADU) + one detached ADU, or one converted ADU + two detached ADUs. Rules for ADUs on lots with apartment buildings do not change.
AB 956 also widens the protection against HOA rules and deed restrictions that effectively prohibit or unreasonably restrict ADUs. That protection now covers any zone where a single-family home is a permitted primary use, not only single-family zones.
2. Lower impact fees for ADUs over 750 sq ft (SB 1117)
ADUs of 750 sq ft or less were already exempt from impact fees. Larger ADUs paid a fee proportional to their full size. Under SB 1117, for lots with up to two ADUs, the fee on an ADU larger than 750 sq ft is calculated only on the square footage above 750.
Example from a legal analysis of the bill: if a 2,000 sq ft house carries a $20,000 fee, a 1,000 sq ft ADU used to owe about $10,000. Under the new rule it would owe about $2,500. Utility connection fees and capacity charges are not part of this change.
3. Faster, more predictable permits
- AB 1621 — a city may not require more than two plan-check and specification reviews for a housing project’s building permit, and inspectors generally cannot require changes that depart from the approved plans.
- SB 1014 — on request, the city must give a non-binding estimate of required on-site and off-site improvements, and after the application is complete it must list them and generally cannot add new ones later.
- AB 1815 and AB 2058 — for factory-built structures, cities generally cannot add local building standards beyond state code without specific findings, and local fees for factory-built housing are limited.
4. Do Los Angeles rules change automatically?
Cities and counties must update their local ADU ordinances to match state law. According to a legal analysis of the 2026 bills, a local ordinance that does not comply becomes null and void on January 1, 2027, and state standards apply instead. LA County published updated ADU guides in 2026. In the City of Los Angeles, permits are handled by LADBS and zoning by City Planning — check their current ADU information before you design, because hillside, fire-zone and coastal properties can have additional requirements.
5. What this means if you own a house in LA
- A larger lot can now hold two rental units in the backyard, not one — useful for family members, rental income or both.
- ADUs between 750 and 1,200 sq ft become cheaper to permit, which can make a two-bedroom ADU pencil out better.
- HOAs have less room to block an ADU, though private HOA disputes are still between owners and the association.
- Plan check should have fewer surprise rounds, but a complete, well-prepared set of plans still matters most.
How BFF can help
BFF Construction and Design is a licensed general contractor (CSLB #1109001) based in Sylmar. We check what your lot allows, prepare plans and engineering, handle LADBS or county permits and build the ADU with our own crew — including light-gauge steel-frame ADUs with our partner ECOLIT. The first visit and estimate are free.
Frequently asked questions
When do the new ADU laws take effect?
January 1, 2027. The bills (AB 956, SB 1117, AB 1621, SB 1014 and others) were signed in September 2026.
Can I build two detached ADUs in Los Angeles in 2027?
On a lot with one single-family house, state law will require cities to approve two detached, newly built ADUs by right, subject to limits such as up to 800 sq ft each, setbacks of up to 4 feet and height limits. Your specific lot may have other constraints, so confirm with LADBS or the county.
Can I have two detached ADUs and a JADU?
No. The allowed combinations are one converted ADU + one JADU + one detached ADU, or one converted ADU + two detached ADUs.
How much will I save on impact fees?
For an ADU larger than 750 sq ft on a lot with up to two ADUs, impact fees are calculated only on the area above 750 sq ft. Connection fees and capacity charges are separate and are not reduced by this law.
Can my HOA stop me from building an ADU?
State law makes HOA rules and deed restrictions unenforceable if they effectively prohibit or unreasonably restrict ADUs, and AB 956 extends that protection. Reasonable restrictions may still apply.
Is this legal advice?
No. This article summarizes public sources. Rules depend on your address and city, so verify with the permitting agency or a qualified professional before you build.
