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Accessory Dwelling Unit (ADU) Permit in Boulder, Colorado

Required for construction of a new attached or detached ADU on a residential property in the City of Boulder. ADUs are permitted by-right in most residential zoning districts (except RH-6, MH, BMS, BCS, IS-1, and IM). As of September 1, 2023, ADUs are reviewed and approved through the standard building permit process without a prior administrative review step, and off-street parking and owner-occupancy requirements were removed for all ADUs.

Verified 2026-06-30 · Source

When you need this permit

  • Permitted by-right on lots with detached dwelling units in most zoning districts — verify via the city's interactive zoning map
  • Detached ADU: maximum 800 sq ft (standard); up to 1,000 sq ft for an affordable ADU (75% AMI) or on a historic property
  • Attached ADU: maximum 1/2 of the principal structure's floor area or 1,000 sq ft, whichever is less (standard); up to 2/3 of principal floor area or 1,200 sq ft, whichever is less, for an affordable ADU/historic property
  • Height: detached ADU 20 ft standard, up to 25 ft with an 8:12 or steeper roof pitch; attached ADU up to 35 ft (same as principal structure)
  • As of Sept. 1, 2023, off-street parking and owner-occupancy requirements were removed for all ADUs
  • Short-term rental (under 30 days) of an ADU is prohibited unless the short-term rental use was established before February 1, 2019
  • Long-term rental of the ADU and/or principal unit is permitted; a rental license is required to rent
  • An ADU may not be sold or conveyed separately from the principal dwelling unit
  • Homeowner self-permitting does NOT apply to detached ADUs — a licensed contractor is required for detached ADU construction (the primary-residence homeowner exception is limited to the owner's single-family detached home and its accessory structures other than a detached ADU) Contractor

Required documents

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Fee schedule

Building Permit Fee — valuation-based (same table as new construction)2026 Schedule of Fees — ADU is explicitly listed under the R-3 Residential building-use category on the City of Boulder Valuation Table (e.g., $170.80–$182.23/sf for Type V-B construction)
Varies by valuation — see Residential Building Permit fee tiers (City of Boulder Valuation Table, R-3 ADU use category)
Plan Check Fee2026 Schedule of Fees, Plan Check Fee
25% of the Building Permit Fee (single-family residential, initial application) or per applicable Compatible Development rate
Energy Code Fee — Residential2026 Schedule of Fees, Energy Code Fee
$83.90

Review timeline

Plan reviewTypical estimate — confirm current times with the Boulder building department
~1–1 business days

How long did your Accessory Dwelling Unit (ADU) Permit permit actually take in Boulder?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

  1. 1

    Foundation

    Footings and foundation before concrete pour

  2. 2

    Framing

    Structural framing, egress, fire separation (if attached)

  3. 3

    MEP Rough-In

    Mechanical, electrical, plumbing rough-ins before walls closed

  4. 4

    Final

    All work complete; Certificate of Occupancy required before occupancy

See the full Boulder inspection guide — scheduling & re-inspection fees →

Tips

  • Since Sept. 1, 2023, Boulder ADUs go straight through the standard building permit process — no separate administrative zoning review is required first, and owner-occupancy/parking requirements were dropped citywide.
  • A detached ADU CANNOT be built under the homeowner self-permit exception, even if you own and occupy the primary home — a licensed contractor is required for the ADU itself. Contractor
  • If you plan to rent the ADU or the principal unit, a separate rental license is required, and (for the principal unit or any licensed rental on the property) SmartRegs energy compliance applies as a condition of that rental license.
  • Short-term rental of an ADU is prohibited unless that specific short-term rental use predates February 1, 2019.

Frequently asked questions

No. As of September 1, 2023, the City of Boulder removed the off-street parking requirement (along with the owner-occupancy requirement) for all ADUs.

In Boulder, the published Building Permit Fee — valuation-based (same table as new construction) is: Varies by valuation — see Residential Building Permit fee tiers (City of Boulder Valuation Table, R-3 ADU use category). Additional published fees: Plan Check Fee — 25% of the Building Permit Fee (single-family residential, initial application) or per applicable Compatible Development rate; Energy Code Fee — Residential — $83.90. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for an accessory dwelling unit (adu) permit in Boulder typically runs 1–1 business days. This is an estimate, not a published figure — confirm current review times with City of Boulder Planning & Development Services at 303-441-1880.

You'll need: Accessory Dwelling Unit (ADU) Application; Site Plan. Depending on your project, Boulder may also ask for: Accessory Dwelling Unit (ADU) Guide; Declaration of Use (for Affordable ADU). See the required-documents checklist on this page for details on each.

Boulder requires 4 inspection(s) for an accessory dwelling unit (adu) permit, in order: Foundation, Framing, MEP Rough-In, Final. Schedule each through City of Boulder Planning & Development Services (303-441-1880).

Apply through City of Boulder Planning & Development Services at 1101 Arapahoe Avenue, Boulder, CO 80302. Phone: 303-441-1880, email: PDSpermitadmin@bouldercolorado.gov. Office hours: Tuesday–Friday, 10:00 a.m.–4:00 p.m.. Official information: https://bouldercolorado.gov/services/building-permits-and-inspections.

Boulder, Colorado has adopted: 2024 International Building Code (IBC) family — City Council adopted the 2024 International Code Council (ICC) suite of codes with local amendments on March 20, 2025 (Ordinance 8684); effective August 1, 2025; local amendments codified in Title 10 of the Boulder Revised Code; 2024 International Residential Code (IRC) — part of the 2024 ICC suite adopted March 20, 2025, effective August 1, 2025, with Boulder amendments in BRC Title 10; 2024 International Mechanical Code (IMC) — part of the 2024 ICC suite, effective August 1, 2025; 2024 International Plumbing Code (IPC) — part of the 2024 ICC suite, effective August 1, 2025; 2024 International Fuel Gas Code (IFGC) — part of the 2024 ICC suite, effective August 1, 2025; 2024 International Fire Code (IFC) — part of the 2024 ICC suite, effective August 1, 2025; 2024 City of Boulder Energy Conservation Code (CoBECC) — Boulder's own locally-amended energy code (not a straight IECC adoption), effective December 1, 2024; published on ICC Digital Codes as COBECC2024P1; mandatory-measures checklist now required to be integrated into commercial/multifamily plan sets; 2023 NFPA 70 National Electrical Code (NEC), as amended by the City of Boulder — effective August 1, 2023; amendments in BRC Title 10; 2021 International Wildland-Urban Interface Code (IWUIC) — applies to properties in Boulder's designated wildland urban interface zone per the city's Structure Protection Plan / Wildland Fire program (edition as referenced in Boulder's Zoning and Permitting FAQ, Oct. 2020; confirm current edition at time of application). Local amendments apply — see the Boulder overview page for the full list.

No — the homeowner self-permit exception in Boulder applies only to a single-family detached home and its accessory structures other than a detached ADU. Detached ADU construction requires a licensed City of Boulder contractor.

Sources & verification

Verified against official sources. Last reviewed 2026-06-30.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Boulder building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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Accessory Dwelling Unit (ADU) Permit in other cities

Arvada, ColoradoAurora, ColoradoColorado Springs, ColoradoCommerce City, ColoradoCortez, ColoradoDenver, ColoradoFort Collins, ColoradoFruita, Colorado

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