ADU permit comparison — all cities
| City + state | Permit type | Max size | Owner occupancy | Parking | Setback minimums | Permit fees | Plan review timeline | State preemption framework | Full city guide |
|---|---|---|---|---|---|---|---|---|---|
| Atlanta, GA | Residential building permit through the Atlanta Office of Buildings, filed via the Atlanta Permitting Portal. Both attached ADUs… | The smaller of 750 square feet of gross floor area or 50% of the gross floor area of the primary dwelling. If the… | Not required. Atlanta's 2023 zoning update does not require the property owner to reside on site as a condition of… | One off-street parking space is required for the ADU. Verify whether the specific parcel or zone qualifies for a parking reduction with… | Detached ADU: minimum 5-foot rear setback. Side setbacks follow the standard requirements for the applicable residential zone district.… | $500–$1,800 estimated combined fees (permit + plan review) for a typical new ADU in Atlanta; excludes any Historic Preservation review or variance… | 10–20 business days for standard residential plan review | Georgia SB 70 (enabling; not full preemption) | Full guide |
| Austin, TX | Separate residential new-construction / addition permit for a dwelling unit, filed through Austin Build + Connect rather than treated… | Austin's ADU guidance does not publish one simple citywide ADU square-foot cap. It says required size is based on… | Austin's ADU and HOME pages reviewed for this page do not headline a standalone owner-occupancy requirement for the… | Austin's ADU guidance reviewed here does not publish a universal citywide parking waiver for all ADUs. Confirm parking, access, and… | Austin says zoning no longer requires a minimum distance between units. Base zoning setbacks, site-development rules, and IRC /… | Austin does not publish a simple flat ADU fee on the ADU page; plan review fees are generated at submittal and permit fees are generated at… | 15 business days per initial new-construction review cycle | Texas HB 2127 context | Full guide |
| Boston, MA | Residential building permit through Boston Inspectional Services Department (ISD), filed in person at 1010 Massachusetts Avenue. Both… | 900 square feet of gross floor area, or the gross floor area of the principal dwelling unit, whichever is smaller.… | Required under Article 25. The property owner must reside in the principal dwelling or the ADU. This is a meaningful… | One off-street parking space is required for the ADU unless the lot is within a Boston Transit Overlay District, in which case no… | The ADU must comply with the setback requirements of the underlying zoning subdistrict. Boston's residential subdistricts typically… | $650–$1,900 estimated combined fees (building permit + plan review + state surcharge) for a typical new ADU in Boston; excludes any ZBA variance or… | 5–15 business days for standard residential plan review | No statewide preemption; Boston Article 25 controls | Full guide |
| Denver, CO | Residential building permit (new construction or addition) through Denver Building & Fire Code, with concurrent zoning review by… | DADU: 864 square feet of gross floor area, or 50% of the primary dwelling's gross floor area, whichever is greater… | No owner-occupancy requirement under Denver Zoning Code 5.4. Colorado HB24-1152 (2024) also prohibits municipalities… | No additional off-street parking is required for an ADU in Denver's urban and suburban zone districts under current Denver Zoning Code… | DADU: minimum 5 feet from rear lot line and 5 feet from each side lot line under Denver Zoning Code 5.4. Front setback must meet the… | Denver permit and plan review fees are valuation-based. A new detached ADU valued at $150,000–$250,000 typically generates $2,000–$5,000+ in… | 4–8 weeks for standard plan review; concurrent review by zoning and building is standard practice | Colorado HB24-1152 | Full guide |
| Los Angeles, CA | Separate LADBS ADU permit / plan-check path governed by LAMC 12.22 A.33 and state ADU law, not a simple accessory-structure filing. | California state law requires local rules to allow attached ADUs of at least 850 square feet (or 1,000 square feet for… | California HCD says local agencies generally cannot impose owner-occupancy requirements on ADUs. JADUs are different… | LADBS says no parking is required for a new ADU within a half-mile walking distance of public transit, and replacement parking is not… | State ADU law generally limits side and rear setbacks for many newly constructed ADUs to no more than 4 feet. No new setback is required… | Los Angeles ADU fees are project-specific; verify current permit, plan-check, and utility costs with LADBS and the applicable utility departments… | Varies by LADBS review path and correction rounds | California ADU law (SB 897 / AB 2221 / SB 9) | Full guide |
| Portland, OR | Residential building permit through Portland Bureau of Development Services (BDS). Attached and detached ADUs both follow the… | 800 square feet of living area or 75% of the living area of the primary dwelling, whichever is less. Garage and… | No owner-occupancy requirement. Portland removed this requirement in 2018. Oregon HB 2001 (2019) further prohibits… | No additional parking required for an ADU. Portland eliminated its ADU parking requirement prior to statewide mandate. | Detached ADU: rear setback of 5 feet; side setbacks per base zone (typically 3–5 feet depending on the zone). Front setback must meet the… | Portland BDS permit and plan review fees are valuation-based. A new detached ADU valued at $150,000–$250,000 commonly generates $2,000–$5,000+ in… | 4–8 weeks for standard plan review; over-the-counter review may be available for simple attached ADU conversions | Oregon HB 2001 | Full guide |
| Seattle, WA | Residential building permit (new construction or addition) through Seattle DCI. AADU and DADU both follow the standard residential… | DADU: 1,000 square feet of gross floor area, maximum 24 feet in height under SMC 23.44.041. AADU size is limited to no… | No owner-occupancy requirement. Washington HB 1337 (2023) prohibited cities from requiring the property owner to live… | No additional off-street parking is required for an ADU under Seattle zoning. Existing required parking serving the primary dwelling must… | DADU: minimum 5 feet from rear lot line and 5 feet from each side lot line per SMC 23.44.041. Front setback must meet the standard zone… | Seattle DCI permit and plan review fees are valuation-based. A detached ADU valued at $150,000–$250,000 typically generates $2,000–$5,000+ in… | 10–20 business days for standard residential plan review; over-the-counter review may be available for simple projects | Washington HB 1337 | Full guide |
| Washington, DC | Residential building permit through the DC Department of Buildings (DOB), filed online through the DC Access portal. DC terminology… | DC's 2016 Zoning Rewrite governs accessory apartment size through the subordinate-use standards in 11 DCMR. The… | Not required. DC's 2016 Zoning Rewrite explicitly removed the owner-occupancy requirement that had applied to… | Additional off-street parking is generally not required for an accessory apartment in DC's urban residential zones. Verify whether the… | Accessory apartments must comply with the rear yard and side yard setback requirements of the applicable 11 DCMR subtitle for the zone… | $1,100–$2,700 estimated combined fees (permit + plan review + technology surcharge) for a typical new accessory apartment in Washington, DC… | 4–8 weeks for standard plan review; DOB posts current queue estimates at dob.dc.gov | N/A — DC local code only | Full guide |
Fees, thresholds, and timelines are summarized from official-source seed data. Verify with your city before building.
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Disclaimer: This page aggregates data from official city sources for informational purposes only, not legal advice. Permit rules, fees, and processes change. Verify with your city's permitting office before building.