ADU rules and law
What the law lets you build: state standards, local ordinances, eligibility, permit clocks and the bills changing them.
The largest cluster here, because it is the one that decides whether a project happens at all. State standards, local ordinances, what disqualifies a lot, the permit clocks agencies have to meet, and the bills moving through the legislature that change any of it. Statute is cited to the section throughout.
Start here: How to build an ADU in Los Angeles
37 posts on adu rules and law
Washington Lets You Sell the Backyard Cottage. The Land Stays Put.
Washington's HB 1337 forces most cities to let a homeowner sell a backyard cottage as a condominium, separate from the house in front. The land stays with the original owner, and the open question is who lends on it.
September 7, 2026
California Will Allow 2 Detached ADUs in 2027. HOAs Lose Ground.
Governor Newsom signed AB 956 on September 29, 2026. Starting January 1, 2027, it doubles the detached ADUs a city must approve to two, and widens the rule that voids HOA bans on compliant units.
September 4, 2026
In San Diego, the City Rewards Affordable ADUs. The County Doesn't.
Inside San Diego city limits, one affordable ADU can earn bonus market-rate units. In the unincorporated county, that lever disappears: same state floor, no bonus program, and a different permit counter entirely.
August 27, 2026
LA County May Limit ADUs on Split Lots. Altadena Is Watching.
Los Angeles County is drafting rules that could limit accessory dwelling units on subdivided lots, even as Eaton Fire survivors in Altadena lean on lot splits and ADU-first permits to rebuild. No hearing is scheduled.
August 26, 2026
Your 2026 California ADU Needs Rooftop Solar. Unless It's Small.
Starting January 1, 2026, a new detached ADU in California is a brand-new home to the energy code: rooftop solar, a heat-pump water heater, and HERS testing, unless it is small enough to be exempt.
August 25, 2026
As of August 17, Your NYC Basement ADU Needs a Radon Certificate
New York City just added a step to below-grade ADU permits: as of August 17, a basement or cellar unit in an Alteration-CO or New Building filing in DOB NOW must carry a certified radon and vapor test before it can reach a certificate of occupancy.
August 24, 2026
Your NYC Basement Can Stay Rented. The Sprinkler Clock Is 2 Years.
New York's basement pilot lets a pre-2024 unit stay rented while you legalize it over ten years. The catch is the required sprinkler system, due early, which redesigns a finished basement more than any permit does.
August 21, 2026
In Oceanside, a $732K ADU Became a Home the Family Can't Sell
Outbid repeatedly on the coast, an Oceanside couple spent about $732,000 turning a garage on his parents' lot into a two-level home. California law lets the finished ADU be rented, but not sold on its own unless Oceanside adopts a condo ordinance.
August 19, 2026
Built an Unpermitted ADU Before 2020? California Offers Amnesty
California's AB 2533 lets homeowners legalize an unpermitted ADU or JADU built before January 1, 2020 without impact fees or code penalties, unless a real health or safety hazard is at stake. Here is the walkthrough.
August 18, 2026
Your Oregon HOA Cannot Ban Your ADU Anymore. Starting 2027.
A 2025 Oregon law voids the deed and homeowners association covenants that quietly ban backyard homes, and it reaches even the decades-old ones. The catch: the ban does not lift until January 1, 2027.
August 10, 2026
San Diego Capped Its ADU Bonus. A 136-Unit Project Shrank to 125.
San Diego's ADU bonus once let a developer stack 136 units on two Pacific Beach lots. After a court injunction and a citywide cap, the project shrank to 125, and the neighbors are still suing.
August 8, 2026
Your Brooklyn Garden Apartment Needs 7 Feet Before It Needs a Kitchen
In New York, a cellar can be rented only as a permitted cellar ADU with a certificate of occupancy, and a basement only qualifies at a 7-foot ceiling. Here is how to plan a Brooklyn garden-apartment ADU the code will sign off on, and where the money really goes.
August 7, 2026
Does Your California ADU Need a Soils Report? The Slope Decides
Most flat-lot California ADUs skip the geotechnical soils report entirely. Put that same unit on a slope or a mapped seismic hazard zone, and expect the city to want a report before your plans mean a thing.
August 4, 2026
Rural Washington Gets a Statewide ADU Rule. If the County Opts In.
Washington HB 1345 lets counties allow a detached cottage on rural land outside the urban growth boundary under one set of state rules, where before it was left to each county. The catch: your county has to opt in first.
July 29, 2026
One Affordable ADU Buys a Market-Rate One in San Diego. For a Fee.
San Diego still trades one affordable ADU for a market-rate bonus unit, but single-family lots are now capped at four to six ADUs and JADUs. The 2025 reforms now in effect added a Community Enhancement Fee and parking to the smallest units, and the coast is frozen.
July 26, 2026
Washington Cities Must Allow Two ADUs Per Lot, No Owner Required
HB 1337 forces Washington cities in growth areas to allow two ADUs on a single-family lot, bans owner-occupancy rules, and caps ADU impact fees at half what the main house pays. Seattle already rewrote its code.
July 24, 2026
Your SF Apartment Building Can Add ADUs. For Five-Plus Units, 25% Is the Floor.
California law makes San Francisco approve at least one ADU inside an existing apartment building, and up to 25 percent of its units, and the city's own program lets buildings of five or more units go further. The catch: on the Waiver track, those new units are rent controlled for good.
July 21, 2026
NYC Will Permit a New Cellar ADU. Legalizing an Old One Waits.
New York quietly opened filings on April 9 for a new one-family home built with a cellar apartment, after Local Law 80 lifted the cellar-rental ban that had blocked them. The pilot to legalize an existing basement unit is still frozen, waiting on the city's rules.
July 18, 2026
Signed: SB 1090 Pauses Altadena Subdivisions Until 2030. Not ADUs.
A law to keep predatory developers out of fire-scarred Altadena, signed September 30, 2026, pauses SB 1123 subdivisions in ZIPs 91001 and 91003 until 2030. It spares your backyard ADU, and SB 9 lot splits too.
July 16, 2026
In LA, a Power Line Can Cost Your ADU Five Feet
Overhead power lines are quietly reshaping Los Angeles ADUs. One Westwood architect waited four months for a utility permit, then had to move her 715-square-foot unit rather than lose five feet of height.
July 10, 2026
California Just Made Coastal ADUs Easier to Permit. On Paper.
California owed coastal homeowners a simpler ADU permit by July 1. It met the deadline with guidance, not a mandate, so whether your Palisades or Sunset lot feels it hinges on your city rewriting its coastal rules.
July 7, 2026
San Francisco Will Let You Sell an In-Law as a Condo. LA Won't.
San Francisco now lets owners sell a new detached in-law unit as a separate condo, but only if its permit application was submitted on or after May 1, 2025. Who it helps, what it does to your exit math, and why Los Angeles still says no.
July 3, 2026
NYC ADU Eligibility: What Actually Disqualifies a Lot
Local Laws 126 and 127 set New York City's ADU rules, but zoning, flood maps, and historic districts disqualify plenty of lots before square footage ever comes into play. Here is what rules a property out.
July 2, 2026
NYC Requires a Licensed Architect for Most ADU Permits
In New York City, filing an ADU permit without a licensed architect is not an option. Here is what triggers the requirement, which zones allow backyard ADUs, and what professional fees look like in 2026.
June 30, 2026
California ADU Law Doesn't Reach Condos, Carlsbad Court Rules
A San Diego County judge ruled that California's 2019 ADU protections don't apply to condo developments or mixed-use zoned lots. The Carlsbad case cost one homeowner $100,000 and ends with a loss.
June 28, 2026
NYC ADUs in Historic Districts: The Map, the Team, and What's Allowed
New York City's Landmarks Preservation Commission launched an online ADU map for historic districts and a dedicated homeowner team on June 25, part of Mayor Mamdani's Block by Block plan released May 26.
June 25, 2026
SB 79 in San Diego: July 1 Upzoning, Up to 52 New Bus Stops
San Diego's SB 79 upzoning takes effect July 1, covering transit corridors where 52 more bus stops could now qualify. Mission Valley, North Park, and Hillcrest are in immediate scope. Here is what changed.
June 23, 2026
Why RPA Finds Most NYC Homeowners Can't Build an ADU Under City of Yes
City of Yes for Housing Opportunity promised New Yorkers the right to add ADUs to their homes. A Regional Plan Association analysis finds that only 12% of the city's one- and two-family properties actually qualify.
June 21, 2026
LA Low-Rise Ordinance: SB 79, Transit Zones, and Your ADU Plans
The LA City Council voted 13-0 on June 3 to advance the Low-Rise Ordinance, capping SB 79 density at 4 stories near transit. With the state law effective July 1, here is what ADU owners near Metro lines face.
June 19, 2026
How to Legalize a Basement Apartment in NYC Under Local Law 126
Under Local Law 126, NYC homeowners in 15 community districts will be able to legalize existing basement apartments while they stay occupied. Here is how the ATR process will work, what the 10-year timeline looks like, and why applications have not opened.
June 18, 2026
How California's Ministerial ADU Approval Works in Practice
California's ministerial ADU permit process gives local agencies hard deadlines: 15 business days to determine completeness, then 60 days to approve or deny. Here is how the clock works after SB 543.
June 16, 2026
California Coastal ADU Guidance: What SB 1077 Means for Your Project
The Coastal Commission's final ADU guidance under SB 1077 is due this month. Here is what the bill requires, what changes for coastal property owners, and what to watch when it drops.
June 4, 2026
HOA vs. ADU in California: AB 956 No Longer Covers Condo Owners
A San Diego judge ruled in April that California's ADU law doesn't protect condo-owners from HOA bans. AB 956 was written to close that gap, but the version Governor Newsom signed on September 29, 2026, dropped its condo provision.
June 1, 2026
In San Diego County, Your ADU Can Now Be Sold as a Condo
San Diego County's Board of Supervisors unanimously adopted an AB 1033 ordinance on March 4, 2026, letting homeowners in unincorporated areas sell their ADU separately as a condominium starting April 4.
May 30, 2026
California's 2026 ADU Handbook: Permit Clocks, Fee Caps, JADU Changes
California's 2026 ADU Handbook dropped on April 7 with updates covering SB 543's 60-day permit deadlines, AB 462's coastal approval window, and new JADU owner-occupancy rules under AB 1154.
May 28, 2026
AB 462: Urgency ADU Bill Unlocks Fire-Rebuild and Coastal Permits
AB 462, signed October 10, 2025 as an urgency measure, took effect immediately. It lets a detached ADU on a disaster-rebuild lot get a certificate of occupancy before the primary dwelling (only in a county under a Governor's emergency proclamation made on or after February 1, 2025), and forces a 60-day clock on coastal ADU permits.
October 14, 2025
SB 543 Just Put LA on a 15-Day Clock for ADU Permits
SB 543, signed October 10, 2025, forces LADBS to determine ADU permit completeness in 15 business days. Miss the deadline and the application is deemed complete by operation of law.
October 12, 2025