Accessory Structures in Boulder, CO (2026)
9 verified accessory structures rules for Boulder, Colorado, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Boulder allows ADUs on most residential lots. The city adopted progressive ADU regulations permitting both attached and detached units with streamlined permitting for smaller units under 500 square feet.
Boulder ADU / Accessory Dwelling Rules
Some RestrictionsADU Permits
Boulder regulates accessory dwelling units under Boulder Revised Code (BRC) Title 9 Land Use Code, primarily Section 9-6-3(n). City Council adopted sweeping ADU reforms in February 2025 that apply to any ADU proposed on or after March 8, 2025: owner-occupancy is no longer required (per Colorado HB24-1152), parking minimums were eliminated, and the prior administrative review step was removed. ADUs are now reviewed through the standard building permit process at Planning & Development Services, 1739 Broadway. Both attached and detached configurations are permitted, with unit-concentration caps tracked by neighborhood area.
ADU Permits in Boulder
Some RestrictionsADU Impact Fees
ADU permits in Boulder trigger building permit fees, plan review fees, Boulder water and sewer plant investment fees, and the Development Excise Tax under the Planning and Development Services Schedule of Fees. Permit fees for a typical ADU run roughly $1,900-$3,200. Critically, City Council's Ordinance 8712 (adopted November 6, 2025) established a new citywide affordable housing impact fee of $11 per square foot on replacement homes and substantial additions — but explicitly EXEMPTS the area of a new ADU from this fee. The exemption applies to complete permit applications submitted on or after January 31, 2026.
ADU Impact Fees in Boulder
Some RestrictionsADU Owner Occupancy
Boulder no longer requires owner occupancy for ADUs. The February 2025 amendment to BRC 9-6-3(n), effective for any ADU proposed on or after March 8, 2025, removed the prior owner-occupancy condition, conforming Boulder's code to Colorado HB24-1152. Both the principal dwelling and the ADU may now be rented to non-owner tenants without any city restriction tied to the owner's residence. This is a significant change in a city historically known for tight rental controls.
ADU Owner Occupancy in Boulder
Few RestrictionsADU Rental Restrictions
Long-term rental of a Boulder ADU (30+ days) requires a city Rental Housing License under BRC Title 10 Chapter 3, which mandates inspection on the IPMC standard plus SmartRegs energy compliance, with renewal every 1-4 years. Short-term rental (under 30 days) is more restrictive: BRC 10-3-18 requires the host to use the unit as their primary residence, hold a Short-Term Rental License, and collect the city's lodging tax. Boulder is the strictest STR jurisdiction on the Front Range, and ADU short-term rental is generally limited to owner-occupied configurations.
ADU Rental Restrictions in Boulder
Heavy RestrictionsShed Rules
Boulder allows small sheds without permits (typically under 120 to 200 sq ft). Larger structures need building permits. Setback requirements apply.
Boulder Shed & Outbuilding Rules
Few RestrictionsGarage Conversions
Boulder may allow garage conversions with permits. Colorado has no statewide garage conversion mandate. Replacement parking may be required.
Boulder Garage Conversion Rules
Some RestrictionsCarport Rules
Boulder requires permits for carport construction. Setback requirements, height limits, and lot coverage maximums apply.
Boulder Carport Construction Rules
Some RestrictionsTiny Homes
Boulder regulates tiny homes differently based on whether they are on a permanent foundation or on wheels. Zoning and minimum square footage requirements apply.
Boulder Tiny Home & Small Dwelling Rules
Some RestrictionsLooking for Boulder County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Boulder city rules.
Accessory Structures in Boulder County →