ADU Rules by City

Max size: Not established — no ADU ordinance exists; confirm with Birmingham Planning Division · Setbacks: Underlying district accessory-structure setbacks apply; ADU-specific standards do not exist yet — confirm with Birmingham Planning Division

Max size: N/A — detached ADUs prohibited (Sec. 73.5; Sec. 10.6.3 bans kitchens in detached accessory structures) · Setbacks: N/A for ADUs — rear dwellings prohibited

Max size: 1,000 sq ft gross floor area or 50% of the principal structure's floor area, whichever is less (Sec. 64-4-2.B.3(a)) · Setbacks: Same as underlying zoning district rear-yard setback, or Historic District Overlay if applicable (Sec. 64-4-2.B.4(a)) — confirm district value with Mobile Planning & Zoning

Max size: 75% of the single-family dwelling's gross floor area (interior habitable area) or 1,000 sq ft, whichever is less · Setbacks: 5 feet minimum (uninhabitable space attached to an ADU, e.g. a garage, must meet full district setbacks)

Max size: 75% of the primary residence's gross square footage (state law guarantees at least the lesser of 1,000 sq ft or 75%) · Setbacks: 5 feet maximum required (ARS 9-461.18 caps rear setbacks at 5 ft)

Max size: 75% of primary residence's interior habitable area or 1,000 sq ft, whichever is less · Setbacks: 5 feet minimum for new structures; existing-structure conversions require no additional setback

Max size: 1,000 sq ft on lots up to 10,000 sq ft (75% of primary dwelling, whichever is less); on lots over 10,000 sq ft, the lesser of 3,000 sq ft or 10% of net lot area · Setbacks: 5 feet (3 ft for some detached configurations per ZO 706; statute caps rear/side at 5 ft)

Max size: 1,000 sq ft or 75% of primary dwelling (whichever is less); 500 sq ft for second/third ADU · Setbacks: 5 feet (detached ADU may be as close as 5 ft to rear lot line)

Max size: 1,000 sq ft or 75% of the main dwelling's gross floor area, whichever is less · Setbacks: 5 feet minimum (all districts, unless the district allows less)

Max size: 75% of primary dwelling, up to 1,000 sq ft (minimum 650 sq ft guaranteed) · Setbacks: 5 feet (limited to 5 ft from property line per HB 2720)

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 1,200 sq ft outside the Hillside Overlay; 850 sq ft (studio/1-bedroom) or 1,000 sq ft (2+ bedrooms) within the Hillside Overlay · Setbacks: 4 ft minimum

Max size: 850 sq ft (studio/1-bedroom); 1,000 sq ft (2+ bedrooms); 800 sq ft in Mountain Fire Zone or front-setback locations; +120 sq ft bonus for each extra code-compliant parking space (deed-restricted) · Setbacks: 4 ft

Max size: 1,200 sq ft · Setbacks: 4 feet

Max size: 1,200 sq ft · Setbacks: 4 ft minimum

Max size: 1,200 sq ft (subject to zone lot-coverage limits, but an 800 sq ft/16-ft ADU can never be prohibited); conversions of existing space exempt · Setbacks: 4 ft maximum required, including lot lines adjacent to streets; none for conversions or same-footprint rebuilds

Max size: 1,200 sq ft of habitable space; ordinance also said the ADU may not exceed the primary dwelling's size — a provision HCD flagged as noncompliant, so confirm with Community Development · Setbacks: 4 ft minimum (3 ft allowed at 12 ft height; 5 ft required for 20 ft height)

Max size: 1,200 sq ft · Setbacks: 4 ft for new construction; none for conversions or same-footprint rebuilds

Max size: 850 sq ft (studio/1BR) to 1,000 sq ft (2BR+) per city handout, based on lot FAR/coverage; some builder sources report 1,200 sq ft — confirm with Escondido Planning (760-839-4671) · Setbacks: 4 ft minimum

Max size: 850 sq ft (1 bedroom or fewer) or 1,000 sq ft (2+ bedrooms); an 800 sq ft ADU with 4-ft setbacks can never be precluded; minimum 150 sq ft · Setbacks: 4 ft; none for conversions of existing structures

Max size: 1200 sq ft · Setbacks: 4 ft minimum (detached new construction)

Max size: 1,200 sq ft · Setbacks: 4 ft for new construction; none for conversions of existing structures

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 850 sq ft for a 1-bedroom ADU; 1,000 sq ft for a 2-bedroom ADU, regardless of underlying zoning standards (units over 850 sq ft must add a second bedroom) · Setbacks: 4 ft maximum required for detached new-construction ADUs; none for conversions of existing structures

Max size: 1,200 sq ft maximum (850 sq ft studio/1BR and 1,000 sq ft 2+BR guaranteed; larger units capped at 50% of primary dwelling floor area or 1,200 sq ft, whichever is less) · Setbacks: 4 ft for new construction; none for conversions of existing permitted structures

Max size: Up to 1,200 sq ft; 800 sq ft unit must be allowed on virtually any lot (state law) · Setbacks: No more than 4 ft (state law); none for conversions of legally established existing space

Max size: Up to 1,200 sq ft; 800 sq ft ADU must be allowed on virtually any lot. HCD struck Irvine's lot-size-based ADU size caps · Setbacks: 4 ft maximum required (state law); none for conversions of existing space

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 1,200 sq ft · Setbacks: 4 ft for units ≤16 ft height

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 1,200 sq ft (subject to zone lot coverage above the 850/1,000 sq ft state-guaranteed unit) · Setbacks: 4 ft minimum

Max size: 850 sq ft (studio/1-bedroom); 1,000 sq ft (2+ bedrooms) — per Ontario ADU Handout (Rev. 01.21.2025) · Setbacks: 4 ft minimum

Max size: 1,200 sq ft (new construction on single-family lots); limited to 1,000 sq ft in most Hillside Overlay districts · Setbacks: 4 ft for new construction; none for conversions of existing structures

Max size: 1200 sq ft · Setbacks: 4 ft minimum (detached new construction)

Max size: 1,200 sq ft (at least 850 sq ft is guaranteed regardless of lot-coverage standards) · Setbacks: 4 ft maximum (detached new construction)

Max size: 850 sq ft (studio/1BR) or 1,000 sq ft (2+BR) per city handout — the state floor; minimum 150 sq ft · Setbacks: 4 ft for new construction; none for conversions of existing structures (including same-footprint rebuilds)

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 1200 sq ft; reduces to 800 sq ft if lot coverage exceeded · Setbacks: 4 ft minimum (detached new construction)

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: 1,200 sq ft (state minimum; local program caps at 850-1,000 sq ft) · Setbacks: 4 ft minimum

Max size: 1,200 sq ft · Setbacks: 4 ft

Max size: Up to the FAR of the underlying zone and no larger than the primary unit; 800 sq ft is always allowed (ADU area up to 800 sq ft is FAR-exempt) · Setbacks: 4 ft; none for conversions of existing space

Max size: 1,000 sq ft · Setbacks: 4 ft

Max size: 850 sq ft (studio/1-bedroom) or 1,200 sq ft (2+ bedrooms) · Setbacks: 4 ft; none for conversions of existing structures (including pre-Jan 1, 2020 unpermitted structures being legalized)

Max size: 1,000 sq ft (800 sq ft under the state-exempt ministerial path); accessory-structure conversions exempt from the cap · Setbacks: 4 ft (detached); same as primary dwelling for attached; none for conversions of existing structures

Max size: 850 sq ft (studio/1-bedroom); 1,000 sq ft (2+ bedrooms); an 800 sq ft ADU can never be precluded by lot coverage, FAR, or open-space standards · Setbacks: 4 ft minimum; none for same-location/same-dimension rebuilds

Max size: 800 sq ft (market-rate); up to 1,000 sq ft (affordable ADU program) · Setbacks: Confirm with Boulder Planning (reduced rear setbacks ~3 ft apply to market-rate detached ADUs near alleys)

Max size: 50% of principal dwelling or 1,250 sq ft (whichever is less); 750 sq ft max if principal < 1,500 sq ft · Setbacks: 12 feet

Max size: Up to 1,000 sq ft on lots over 7,000 sq ft (864 sq ft on 6,000-7,000 sq ft lots; ~650 sq ft on smaller lots) — varies by zone district · Setbacks: Must be within rear 35% of lot; 5 ft minimum rear setback

Max size: Larger of 450 sq ft or 30% of the required rear yard (detached accessory building footprint) · Setbacks: Minimum 12 ft from the alley centerline (DCMR Subtitle D 5004.1)

Max size: 25% of primary residence or 750 sq ft (whichever is smaller) · Setbacks: 20 feet

Max size: City of Miami: confirm current cap with City of Miami Planning (proposed ~500 sq ft / 10% of lot, capped at 800 sq ft). Unincorporated Miami-Dade: 400-800 sq ft in RU-1 districts (varies by district) · Setbacks: 5 ft (RU-1 district)

Max size: 1,000 sq ft max, 500 sq ft min; must be smaller than the principal structure (varies by sector) · Setbacks: 15 feet

Max size: 950 sq ft (larger setbacks apply when the ADU exceeds 15% of lot size) · Setbacks: 3 ft (20 ft when the ADU exceeds 15% of lot size)

Max size: 750 sq ft (allowed by-right in R-4, R-4A, R-5 zones) · Setbacks: 4-15 ft (varies by zone: 4 ft in R-5; 15 ft in R-4/R-4A)

Max size: 40% of the principal building's footprint, capped at 700 sq ft / 1 bedroom in most districts (1,000 sq ft / 2 bedrooms in A-1, RSF-E, RSF-20, RSF-30); 400 sq ft minimum (May 2023 amendment) · Setbacks: 4 feet (detached accessory; Confirm with Savannah Planning for your zone)

Max size: 500 sq ft (lots under 5,000 sq ft); 1,000 sq ft (lots 5,000 sq ft and larger) — updated by Ordinance 25-2 · Setbacks: Standard building code requirements

Max size: Detached coach houses governed by bulk/setback standards rather than a flat sq-ft cap (limited to 60% of the required rear setback area); Confirm buildable size with Chicago Dept. of Housing for your lot · Setbacks: Detached ADU must sit within the rear 50% of the lot; Confirm with Chicago Dept. of Housing

Max size: 1,000 sq ft · Setbacks: 12 feet

Max size: Not as-of-right — ZBA variance required (by-right only in Mattapan) · Setbacks: 20 feet (applies to variance/Mattapan detached units)

Max size: 900 sq ft or 50% of primary dwelling, whichever is less (MA state by-right cap) · Setbacks: 5 ft base (ADU setbacks may not be stricter than principal/accessory standards under 760 CMR 71.03)

Max size: 1,000 sq ft or 50% of the main building by right; 1,200 sq ft in an existing garage or if the owner occupies the site; up to 1,500 sq ft by special permit · Setbacks: 5 ft for a 1.5-story/22-ft detached ADU; standard principal-dwelling setbacks for taller units

Max size: 900 sq ft or 50% of the principal structure's gross floor area (per 760 CMR 71.02), whichever is less; minimum 320 sq ft for a detached ADU · Setbacks: Detached ADUs must meet the principal-structure yard setbacks in QZO Table 4.1 — varies by district; Confirm with Quincy Inspectional Services

Max size: Local backyard cottage: 576 sq ft max floor plate, max massing 24 ft wide x 32 ft deep; state protected-use ADU: up to 900 sq ft or 50% of principal dwelling GFA, whichever is smaller (reasonable local dimensional standards still apply) · Setbacks: 3 ft minimum (3 or 20 ft where lot abuts an alley); 10 ft minimum separation from the principal building

Max size: 900 sq ft by-right (larger is possible via Planning Board special permit) · Setbacks: 5 ft via the accessory-structure standard (R districts)

Max size: 600 sq ft on lots up to 7,199 sq ft; 800 sq ft on lots 7,200 sq ft or larger — or the ground-floor area of the main dwelling, whichever is less · Setbacks: Allowed in the rear setback area if at least 3 ft from any lot line and all structures cover no more than 35% of the rear setback area; fire-rated walls required if 3-5 ft from a lot line

Max size: Proposed: no more than the smaller of 1,200 sq ft or 60% of the principal dwelling's gross floor area (Sec. 50-12-466); not yet in effect · Setbacks: Proposed: standard 3 ft accessory-structure rear setback, with no rear setback required where the lot abuts an alley; existing accessory structures converted to ADUs may keep their footprint

Max size: 850 sq ft maximum and no more than 40% of the main house's gross floor area (ordinance §5.9.03 allows at least 400 sq ft in any case); greenspace requirements (30-60% depending on zone) can further limit buildable size · Setbacks: Detached ADU must be at least 3 ft from the rear lot line (special Building Code requirements if a wall is within 5 ft of the property line)

Max size: 1,300 sq ft or 16% of lot area (whichever greater); max 1,600 sq ft or size of primary dwelling (whichever less) · Setbacks: 3 ft (5 ft from alleys for above-garage ADUs)

Max size: 800 sq ft or 75% of the principal dwelling floor area (whichever is greater) · Setbacks: 3 ft from interior lot lines

Max size: 25% of the main single-family home's square footage (excluding carports, garages, unfinished basements), max 1,000 sq ft per Review-Journal reporting; some 2026 secondary sources cite a 1,200 sq ft cap — confirm the current limit with Henderson Community Development · Setbacks: Per underlying zoning district; minimum 6-ft separation from the main residence required — confirm exact district setbacks with Henderson Community Development

Max size: Amended by Ordinance 6963 (July 2026) - codified text pending; the pre-2026 rule capped all accessory structures at 50% of the principal dwelling's floor area · Setbacks: 3 feet minimum for detached accessory structures, plus 6-ft separation from the main dwelling; no setback required from a property line abutting an alley

Max size: No square-footage cap — size is limited by the 18 ft/2-story height limit, setbacks and lot coverage (R-1: maximum lot coverage increases by an additional 5% for an ADU; R-2: 80% lot coverage; RH-1: 75% lot / 55% building coverage; RH-2: 75% lot coverage) · Setbacks: R-1: 2 ft (per building code); R-2: 3 ft; RH-1 and RH-2: none

Max size: 300-800 sq ft, and no more than 40% of the habitable area of the principal building, whichever is less; no more than 3 rooms excluding kitchen and bathroom; detached ADUs must be located in the rear yard · Setbacks: Accessory-building setbacks of the underlying zone apply — confirm with the Montclair Department of Planning & Community Development

Max size: 800 sq ft or 25% of the principal dwelling's total floor area, whichever is greater; +5% total floor area if the ADU is fully accessible under NJ's Barrier Free subcode; 1,000 sq ft or 30% if deed-restricted to low/moderate-income occupancy (Ord. 2024-32) · Setbacks: Per the accessory-structure setbacks of the underlying district — confirm with the Princeton Planning Department; detached ADUs must be at least 5 ft from the habitable portion of the main house

Max size: 1,000 sq ft gross floor area; a detached unit must also be shorter and smaller-footprint than the principal building (Green Code UDO 6.1.2.B) · Setbacks: 15 feet

Max size: Up to 800 sq ft (and no more than 33% of the required rear yard) where permitted under City of Yes; not allowed in historic districts or R1A/R2A/R3A zones outside the Greater Transit Zone · Setbacks: N/A

Max size: Not applicable yet - the pending Zoning Alignment Project code would newly allow ADUs (by special permit in low-density zones); no adopted dimensional standards exist · Setbacks: 15 feet

Max size: 1,000 heated sq ft, and no more than 50% of the principal dwelling's floor area (whichever is less) when in an accessory structure · Setbacks: 15 feet

Max size: Up to 1,200 heated sq ft (UDO Sec. 5.4.2); must remain subordinate in size to the primary dwelling · Setbacks: 15 feet

Max size: 800 sq ft · Setbacks: 5 feet (rear lot line, per UDO Sec. 3.6.2; 20 ft if abutting an alley with parking, 4 ft alley without parking)

Max size: 800 sq ft or 50% of the primary dwelling's gross floor area, whichever is less · Setbacks: Per underlying zone accessory-structure standards — Confirm with Beaverton Planning Division

Max size: 800 sq ft maximum floor area · Setbacks: Per underlying zoning district; detached ADU must be at least 6 ft from the main house

Max size: 800 sq ft (or 10% of lot area, whichever is smaller) · Setbacks: 10 feet

Max size: 800 sq ft or 75% of primary (whichever is less) · Setbacks: 5 feet

Max size: 900 sq ft (or 75% of the main building gross floor area, whichever is less) · Setbacks: Confirm with Salem Planning (SRC 700.007)

Max size: 1200 sq ft (proposed; not yet adopted) · Setbacks: Varies by zone; typically 20-30 ft

Max size: 850 sq ft on lots under 10,000 sq ft; 1,200 sq ft on lots 10,000 sq ft or larger; and no larger than the size or footprint of the principal structure · Setbacks: 5 ft minimum

Max size: Lesser of 1,100 sq ft or 15% of lot area (HOME Initiative). 2nd-story floor area capped at 550 sq ft. · Setbacks: 10 feet

Max size: 800 sq ft (Dallas caps ADUs at 800 sq ft) · Setbacks: 15 feet

Max size: Commonly cited around 800-1,000 sq ft, but sources conflict - confirm the current cap with Fort Worth Development Services · Setbacks: Must meet the rear setback of the underlying district (commonly 5–10 ft for accessory structures)

Max size: Up to 1,500 sq ft (raised from 900 by the Livable Places Ch. 42 amendments, effective Nov 27, 2023); deed restrictions may be stricter · Setbacks: 5 feet

Max size: 800 sq ft (1,200 sq ft in the RE zone) per UDC §35-371 · Setbacks: 5 feet (detached ADU may be 3 ft or more from side and rear lines per UDC §35-371)

Max size: Up to 1,000 sq ft, or the size of the main building, whichever is less (internal ADUs have no size cap) · Setbacks: Increase 1 ft for each foot of height above 17 ft

Max size: Footprint-based: the greater of 1/3 of the main house's floor area, or 350 sq ft (lots up to 2,500 sq ft) / 500 sq ft (larger lots) · Setbacks: 1 ft minimum; 3 ft if windows face property line

Max size: 35% of combined floor area up to 750 sq ft (45% up to 500 sq ft if the main dwelling is under 1,000 sq ft); new detached accessory buildings are also footprint-capped at 560 sq ft (R-5/R-6) or 650 sq ft (other R districts) · Setbacks: 5 ft (interior lots); 10 ft (corner lots)

Max size: 1,200 sq ft (Director may approve more for single-floor units in the primary structure or conversions/additions to existing accessory structures) · Setbacks: Subject to middle-housing dimensional standards (LUC 20.20.538) — Confirm with Bellevue Development Services

Max size: 1,000 sq ft of floor area above grade (size also constrained by FAR and lot coverage) · Setbacks: 5 feet

Max size: 1,000 sq ft · Setbacks: Confirm with Spokane Planning (SMC Title 17C)

Max size: 1,000 sq ft living area · Setbacks: 15 feet (no setback required from an alley)

Max size: 1,000 sq ft gross floor area · Setbacks: Confirm with Vancouver Planning (VMC 20.810.040)