California state preemption
Updated: Jan 2025 (CA HCD ADU Handbook). Always check your city’s ADU ordinance for objective local standards.
Must allow at least 800 sf notwithstanding FAR/lot coverage. Also at least 850 sf (studio/1-BR) or 1,000 sf (2+ BR).
Detached: 16 ft baseline; 18 ft within ½-mile of transit or on lots with multifamily; +2 ft for matching roof pitch. Attached: up to 25 ft or primary height (lower).
At least 4 ft side & rear for new detached ADUs.
Max 1 space per unit/bedroom; exempt within ½-mile of transit, historic districts, conversions/within primary, when permits aren’t offered, or when car-share within 1 block.
Prohibited for ADUs (no owner-occ requirement).
None for ADUs < 750 sf; otherwise proportional to ADU vs. primary size.
Oregon state rules
Updated: September 2, 2025. ORS 197.312(5) (HB 2001) requires cities ≥ 2,500 and counties ≥ 15,000 within UGBs to allow at least one ADU per detached single-family dwelling, with clear, objective rules. Local codes may not require owner-occ or additional off-street parking for ADUs (limited STR exceptions).
Set locally; common ~800–900 sf or 75–85% of the primary home.
Set locally; often ~20–25 ft under accessory-building standards.
Set locally; rear/side commonly ~4–5 ft.
Not allowed as a condition of ADU approval (limited STR exceptions). HB 2001 FAQ
Not allowed (limited STR exceptions). HB 2001 FAQ
Some cities waive/reduce SDCs; e.g., Portland’s waiver needs a 10-year covenant (no STRs). Portland SDC Waiver
Washington state preemption — RCW 36.70A.680–.681
State law is in effect in GMA urban growth areas. If a city/county hasn’t updated yet, the statewide standards apply.
At least two ADUs per lot (any mix of attached/detached) where single-family homes are allowed in UGAs.
Local codes may not require ADUs smaller than 1,000 sf.
ADUs can’t have stricter setbacks/coverage/design than the principal; height may not be limited below 24 ft or the principal’s height limit.
No on-site parking may be required within ½ mile of a major transit stop; otherwise max 1 space/unit on lots < 6,000 sf and 2 spaces/unit on lots > 6,000 sf.
Not required for the principal home or ADUs (limited STR exceptions may apply).
Impact fees capped at ≤ 50% of the principal unit; no public street improvements may be required as a permit condition.
Colorado statewide baseline (effective Jun 30, 2025)
HB24-1152 requires many metro-area jurisdictions (“subject jurisdictions”) to allow one ADU by-right via an administrative (ministerial) review where single-unit homes are allowed. Separately, HB24-1007 bans family-based occupancy caps statewide (effective Jul 1, 2024). {{verify locally}}
“Subject jurisdictions”: municipalities (pop ≥1,000) in an MPO; and county areas that are both in an MPO and inside a CDP of ≥40,000. {{verify locally}}
One ADU accessory to a single-unit detached home, by administrative approval (no hearing), in zones that allow single-unit homes.
No new off-street space in most cases; designation of an existing space may be required. Owner-occupancy requirements are prohibited with narrow exceptions. {{verify locally}}
Signed May 13, 2024; local compliance/reporting in 2025; by-right requirement begins .
Side ≤ primary’s side; rear ≤ max(other accessory rear, 5 ft). {{verify locally}}
Locals must allow a band that includes 500–750 sf; many allow up to 800–1000+ sf or tie to main-home size. {{verify locally}}
Heads up: Outside “subject jurisdictions,” rules remain local. Fire/wildland overlays, historic districts, and covenants can add standards. {{verify locally}}
Denver city playbook (2025)
ADUs are allowed in many Denver zones (coverage has expanded). Reviews are administrative/objective when standards are met. Exact size/height/setbacks are zone-specific—confirm with the city zoning map. {{verify locally}}
Zone/lot dependent; common detached caps around ~650–864+ sf (districts vary). {{verify locally}}
Typically ~16–24 ft depending on zone and roof form; alley context may affect. {{verify locally}}
Detached ADUs follow accessory-structure setbacks; corner/alley lots can differ. {{verify locally}}
Often you can designate an existing space; new off-street may not be required in some contexts (esp. near transit). {{verify locally}}
Ongoing owner-occ generally not required; confirm any registration/licensing conditions. {{verify locally}}
Privacy, entry placement, and alley-facing design standards can apply on two-story forms. {{verify locally}}
Texas local control
Updated: Sept 2025 (no enacted statewide ADU mandate; Austin parking reform Nov 2023). Always check your city’s ordinance and any HOA covenants.
Set locally by city/county. Example: Austin governs ADU size by zoning district.
Set locally with objective standards (varies by city and zoning district).
Set locally (rear/side-yard distances and easements vary by jurisdiction).
City-specific. Austin eliminated citywide parking minimums in 2023; accessibility rules still apply.
Set locally; HOAs/deed restrictions may impose additional limits.
Local development/utility fees apply; amounts and impact-fee policies vary by jurisdiction.
New York local + programs
Updated: Sept 2025 (NYC City of Yes ADUs; DOB Bulletin 2025-006; NYS “Plus One” ADU program; county ADU tax exemption forms). Local codes govern outside NYC.
Set locally. NYC ADU ≤ 800 sf (one per 1–2 family home).
Set locally. NYC: up to 25 ft (2 stories) for ADUs per City of Yes guide.
Set locally. NYC: typical 5 ft lot-line distance shown in guidance (context-dependent).
Set locally. NYC: No parking required for the ADU under City of Yes.
Local determination and/or program criteria (varies by municipality and grant terms).
Local filing/permit fees apply; Plus One ADU grants (state) and optional county ADU property-tax exemptions (RPTL 421-p) may offset costs.
How to get your ADU permitted (fast)
- Confirm eligibility: Lot zoning, overlays, wildfire/shoreline, utilities.
- Pick a compliant footprint: Choose a size/height that fits the statewide minimums and your city’s objective standards.
- Speed up design: Use pre‑approved plans (if available) or a builder’s plan set with engineering.
- Ministerial submittal: Apply for administrative review with a complete checklist; target 30–60 day approvals.
- Inspections & utilities: Schedule foundation/rough/final; coordinate tie‑ins and any panel upgrades.
Need help? Find vetted builders or request a calibrated estimate.
ADU regulations: quick FAQ
Do I need off‑street parking for an ADU?
In many states (e.g., CA statewide; many WA jurisdictions), parking is waived near transit or for conversions. In others, it’s city‑specific.
Can cities still require me to live on‑site?
California prohibits owner‑occupancy requirements for ADUs. Oregon also disallows them within UGBs. Washington’s HB 1337 removes them in covered jurisdictions. Elsewhere varies.
What if my city’s website conflicts with state law?
State law usually preempts. Bring the statute/handbook to planning or request a supervisor review. We’ve linked official sources and can help escalate.
How big can my ADU be?
California guarantees up to 800 sf regardless of lot limits; at least 850/1,000 sf by bedrooms. Washington caps minimum size standards at 1,000 sf. Oregon leaves size to cities. Others vary.
Are impact fees waived?
CA waives impact fees for ADUs under 750 sf; WA caps some fees. In OR/CO/TX/NY, fees are local.
Accuracy & freshness
This page reflects statewide rules as of . City ordinances can change; always confirm locally before submitting.