Can I Build an ADU (Accessory Dwelling Unit) in Colorado?
ADU permit requirements. State law, internal vs. detached, basement apartments, and impact fee waivers.
Often yes — many states now require cities to allow at least internal ADUs.
State Law May Require It
A growing number of states have passed laws requiring cities to allow at least internal ADUs (within the existing footprint of the home — basement apartments, above-garage units, etc.). Many cities also allow detached ADUs, though rules on size and placement vary. Check whether your state has an ADU-enabling law before assuming your city can simply say no.
Types of ADUs
Internal ADUs include basement apartments, converted attic space, and attached additions. Detached ADUs include backyard cottages, converted garages, and purpose-built accessory structures. Each type has different permit requirements and setback rules.
Key Requirements
Most ADUs need: a separate entrance from the primary dwelling, adequate parking (usually one additional off-street space), fire separation (1-hour rating for internal ADUs), and compliance with all building codes for habitable space. Basement ADUs require egress windows in every bedroom.
Reduced Impact Fees
Some states limit impact fees for ADUs, making them cheaper to permit than a full second dwelling. Many cities waive or significantly reduce impact fees for ADUs. Ask your city about current fee schedules — this can save thousands of dollars.
In many states you can build an ADU thanks to state law requiring cities to allow it. Internal ADUs are the easiest path. Start by checking your state's ADU law and your city's specific ADU ordinance.
Permit fees by city in Colorado
Verified from each city’s published fee schedule. Where a city has no separate fee listed for this project, open the city page for the current requirements and amount.
| City | Permit fee | Source |
|---|---|---|
| Akron | Not a fixed figure — calculated based on construction cost (valuation-based), due at time of application submissionVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Alamosa | $24Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Arvada | Varies by valuation — see Residential Building Permit fee tiers (Table 18-1: $34 minimum up to $5,669.25 + $3.45/$1,000 over $1M)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Aspen | Computed via the City's Building Permit Fee Estimator (Excel) referencing the current Municipal Code Fee Ordinance (Title 2)Verifiedvia Residential Building Permit (New Construction, Single-Family/Duplex/Townhouse) | Residential Building Permit (New Construction, Single-Family/Duplex/Townhouse) → |
| Ault | $23.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Aurora | $1.30 per square foot (R-3 occupancy group rate)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Avon | $50.00Verifiedvia Residential Building Permit (New Structure) | Residential Building Permit (New Structure) → |
| Basalt | $21.00Verifiedvia Residential Building Permit (New Construction, Single-Family/Duplex/Townhome) | Residential Building Permit (New Construction, Single-Family/Duplex/Townhome) → |
| Bennett | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Berthoud | Per the 2024 IRC Appendix AB valuation-based fee tableVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Blue River | $50.00Verifiedvia Building Permit — New Construction (Type A Permit) | Building Permit — New Construction (Type A Permit) → |
| Boulder | Varies by valuation — see Residential Building Permit fee tiers (City of Boulder Valuation Table, R-3 ADU use category)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Bow Mar | $56Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Breckenridge | $50.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Brighton | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Broomfield | $23.50Verifiedvia Residential Building Permit (New Single-Family House) | Residential Building Permit (New Single-Family House) → |
| Burlington | $25Verifiedvia Residential Building Permit (New Construction / Addition) | Residential Building Permit (New Construction / Addition) → |
| Calhan | TBD based on project — per the Town of Calhan's own official Fee Schedule (Updated 11/10/25), the 'Building Permit' line item's CURRENT value is stated verbatim as 'TBD based on project'; the printed Building Permit Application form separately has no new-construction line item and directs applicants to contact the Town office for a project-specific determinationVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Cañon City | 1.0% of valuation (City of Cañon City Permit Fee Multiplier)Verifiedvia Residential Building Permit (New Single-Family Construction) | Residential Building Permit (New Single-Family Construction) → |
| Castle Pines | $42.00Verifiedvia New Residential Building Permit | New Residential Building Permit → |
| Castle Rock | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Centennial | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Center | $0.10 per sq. ft. of floor space to be constructed, $50.00 minimumVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Cheyenne Wells | $25.00Verifiedvia Residential Building Permit | Residential Building Permit → |
| City of Fountain | $80.00 for the first $2,000 plus $8.00 for each additional $1,000 or fraction thereofVerifiedvia Residential Building Permit (New Single-Family/Duplex Construction) | Residential Building Permit (New Single-Family/Duplex Construction) → |
| Colorado Springs | Varies by valuation — see Residential Building Permit fee tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Columbine Valley | $7,600 for the first $1,000,000 plus $5.00 for each additional $1,000 or fraction thereof, plus inspection feesVerifiedvia Building Permit with Plan Review (New Construction) | Building Permit with Plan Review (New Construction) → |
| Commerce City | Same valuation tiers as new residential construction (e.g., $30.41 minimum up to $7,257.12 + $4.72/$1,000 over $1,000,000)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Conejos County (Unincorporated) | $24Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Cortez | $500.00Verified | Accessory Dwelling Unit (ADU) Permit → |
| Craig | $100.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Crested Butte | $28.42Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Cripple Creek | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Dacono | Computed by the Building Official using the ICC Building Safety Journal's Building Valuation Data (BVD), updated bi-annually each August and FebruaryVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Delta | $23.50 for valuation $1.00–$500.00; $23.50 + $3.05 per additional $100 (or fraction) up to $2,000; $69.25 + $14.00 per additional $1,000 (or fraction) up to $25,000; $391.25 + $10.10 per additional $1,000 up to $100,000 (note: fee schedule text repeats this bracket ceiling for the $25,000.01–$50,000 tier); $643.75 + $7.00 per additional $1,000 for $50,000.01–$100,000; $993.75 + $5.60 per additional $1,000 for $100,000.01–$500,000; $3,233.75 + $4.75 per additional $1,000 for $500,000.01–$1,000,000; $5,608.75 + $3.15 per additional $1,000 above $1,000,000Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Denver | Assessed on total ADU construction valuation using ADMIN 125/138 Table 1 — e.g. $35 for $501–$2,000, $35 for the first $2,000 plus $8/each additional $1,000 up to $25,000, scaling up through the table's brackets to $5,385 for the first $1,000,000 plus $3.65/each additional $1,000 over thatVerified | Accessory Dwelling Unit (ADU) Permit → |
| Dillon | $50.00Verifiedvia Building Permit (New Construction / Foundation, Framing, Finish) | Building Permit (New Construction / Foundation, Framing, Finish) → |
| Durango | $24.00Verifiedvia Residential Building Permit (New Single-Family Residence or Duplex) | Residential Building Permit (New Single-Family Residence or Duplex) → |
| Eagle | $39.40Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Eaton | Per Appendix L, 2018 IRC valuation table (as referenced in the Town's current Fee Schedule)Verifiedvia Residential Building Permit (New Construction / Addition / Remodel / Repair / Basement Finish) | Residential Building Permit (New Construction / Addition / Remodel / Repair / Basement Finish) → |
| Edgewater | $35.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Erie | $23.50Verifiedvia Residential Building Permit (New Single-Family / Custom Home / Modular Home) | Residential Building Permit (New Single-Family / Custom Home / Modular Home) → |
| Estes Park | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Evans | $75.00Verifiedvia Residential Building Permit (New Primary Structure) | Residential Building Permit (New Primary Structure) → |
| Federal Heights | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Firestone | $80Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Florence | $75.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Fort Collins | $6,925 (flat fee, mandatory for ADU projects)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Fort Lupton | $24.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Fort Morgan | $27.00Verifiedvia Residential Building Permit (New Single-Family Residence / New House) | Residential Building Permit (New Single-Family Residence / New House) → |
| Frederick | $35.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Frisco | $65.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Fruita | $35.00 minimum, scaling per the valuation tiers in Table 2Verified | Accessory Dwelling Unit (ADU) Permit → |
| Garden City | See city page for the current Residential Building Permit (New Construction / Additions / Structures Over 120 sq ft) fee | Residential Building Permit (New Construction / Additions / Structures Over 120 sq ft) → |
| Gilcrest | $23.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Glenwood Springs | $23.50 minimum, scaling per Table 1-A valuation tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Golden | $25.85 minimum, scaling per the valuation tiers in the Building Permit Fee TableVerified | Accessory Dwelling Unit (ADU) Permit → |
| Grand Junction | $50.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Greeley | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Gypsum | $250Verified | Accessory Dwelling Unit (ADU) Permit → |
| Haxtun | $10.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Holyoke | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Hudson | $35.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Johnstown | $23.50Verifiedvia Residential Building Permit (New Construction / Any New Structure) | Residential Building Permit (New Construction / Any New Structure) → |
| Julesburg | Not published; determined by Town Hall at time of application per a fee schedule adopted by Town Board resolution (not publicly posted online)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Keenesburg | $33.80Verifiedvia New Residential Home Building Permit | New Residential Home Building Permit → |
| Kersey | Set by SAFEbuilt per the Uniform Building Code (UBC) valuation-based fee schedule (not a flat Town-published table)Verifiedvia Residential Building Permit (New Construction / Additions) | Residential Building Permit (New Construction / Additions) → |
| La Junta | Calculated from Total Valuation (Materials $ + Labor $) stated on the application; fees payable to the City of La Junta at time of permit issuanceVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| La Salle | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Lafayette | $30.00 minimum, scaling per valuation tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Lakewood | Varies by valuation — see Residential Building Permit fee tiers ($26.00 minimum up to $5,570.15 + $3.45/$1,000 over $1,000,000)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Lamar | $33.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Larkspur | See city page for the current Residential Building Permit (New Construction — Single Family Residential Attached/Detached) fee | Residential Building Permit (New Construction — Single Family Residential Attached/Detached) → |
| Littleton | $25.85Verifiedvia Residential Building Permit (New Single-Family, Townhouse, Two-Family Dwelling) | Residential Building Permit (New Single-Family, Townhouse, Two-Family Dwelling) → |
| Lochbuie | $33.80Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Lone Tree | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Longmont | $5,000–$10,000Verified | Accessory Dwelling Unit (ADU) Permit → |
| Louisville | $28.00 minimum, scaling per the valuation tiers in the Building Permit Fee TableVerified | Accessory Dwelling Unit (ADU) Permit → |
| Loveland | Based on the current ICC Building Valuation Data (square-foot construction cost by occupancy group/construction type) applied to project square footage; e.g., R-3 (one- and two-family, Type VB) valuation is $175.92/sq ft effective March 15, 2026Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Lyons | $135Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Mead | $44.56Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Milliken | $160.00Verifiedvia Residential Building Permit (New Construction / Any New Structure) | Residential Building Permit (New Construction / Any New Structure) → |
| Montrose | Not resolved — the City's codified Sec. 3-1-1 Fee Schedule PDF (previously hosted at a 2025-effective DocumentCenter link) returns HTTP 404 as of this review, and no Wayback Machine snapshot of that URL exists (checked directly via the CDX API). The Municode-hosted Regulations Manual chapter containing this fee schedule is rendered client-side via JavaScript and did not yield fee-table text through a direct browser-header fetch in this session.Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Morrison | Per the adopted code (2015 IBC valuation-based fee table)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Mount Crested Butte | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Mountain View | $40.00 for total valuation $1.00-$500.00; $40.00 for the first $500.00 plus $2.00 per additional $100.00 (or fraction) from $501.00-$2,000.00; $70.00 for the first $2,000.00 plus $14.00 per additional $1,000.00 (or fraction) from $2,001.00-$25,000.00; $391.25 for the first $25,000.00 plus $10.10 per additional $1,000.00 (or fraction) from $25,001.00-$50,000.00; $643.75 for the first $50,000.00 plus $7.00 per additional $1,000.00 (or fraction) from $50,001.00-$100,000.00; $993.75 for the first $100,000.00 plus $5.60 per additional $1,000.00 (or fraction) from $100,001.00-$500,000.00; $3,233.75 for the first $500,000.00 plus $4.75 per additional $1,000.00 (or fraction) from $500,001.00-$1,000,000.00; $5,608.75 for the first $1,000,000.00 plus $3.65 per additional $1,000.00 (or fraction) above $1,000,000.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Mountain Village | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Nederland | $250.00 non-refundableVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Northglenn | $23.50 minimum, scaling per the valuation tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Nunn | $75.00 flat Admin Fee (permits requiring plan review), plus 2% Use Tax on all Building PermitsVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Palisade | $10.00 flat feeVerifiedvia Residential Building Permit (New Construction) — Town Planning Clearance + Mesa County Building Permit | Residential Building Permit (New Construction) — Town Planning Clearance + Mesa County Building Permit → |
| Parker | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Pierce | UBC fee schedule + $30 or 30% (whichever is greater)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Platteville | $50.00 zoning-compliance surcharge (residential applications only) is a confirmed flat figure; the underlying valuation-based base fee itself is not a Town-published number — verified-negative: it follows Chapter 18's adopted 2024 IBC fee schedule by reference, not a separately republished Town dollar tableVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Poncha Springs | $200.00 flatVerified | Accessory Dwelling Unit (ADU) Building Permit → |
| Pueblo | $73.93 per square foot (valuation basis, Table A)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Rifle | $23.50 minimum, scaling per the City's Building Permit Fee Worksheet valuation tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Saguache | $20.00Verifiedvia Building Permit | Building Permit → |
| Salida | 20% of the county permit fee, minimum $50.00Verified | Accessory Dwelling Unit (ADU) Building Permit → |
| Sedgwick | $30.00Verifiedvia Building Permit (New Construction, Addition, Alteration, Roof/Siding, Foundation, Relocation) | Building Permit (New Construction, Addition, Alteration, Roof/Siding, Foundation, Relocation) → |
| Severance | Valuation-based, determined by SAFEbuilt ColoradoVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Silver Cliff | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Silverthorne | 65% of the Building Permit FeeVerified | Accessory Dwelling Unit / Single Apartment Building Permit → |
| Springfield | $50.00 flatVerifiedvia Building Permit | Building Permit → |
| Steamboat Springs | $21.15Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Sterling | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Superior | $28.50Verifiedvia Residential Building Permit (New Construction / Additions) | Residential Building Permit (New Construction / Additions) → |
| Telluride | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Thornton | Varies by valuation — see Residential Building Permit fee tiers (2026 Fee Schedule)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Timnath | Not published onlineVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Town of Carbondale | $27.50Verifiedvia New Single-Family Dwelling, Duplex, or Townhouse Building Permit | New Single-Family Dwelling, Duplex, or Townhouse Building Permit → |
| Trinidad | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Unincorporated Pueblo County | $73.93 per square foot (valuation basis)Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Unincorporated Teller County | See city page for the current Single Family Dwelling (SFD) / New Residential Building Permit fee | Single Family Dwelling (SFD) / New Residential Building Permit → |
| Unincorporated Washington County | $100.00 flat, for all buildings except Use by Special Review (commercial-use) buildingsVerifiedvia Building Permit (New Construction, Addition, Remodel, Accessory Structures) | Building Permit (New Construction, Addition, Remodel, Accessory Structures) → |
| Vail | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Victor | $23.50Verifiedvia Residential Building Permit (New Single-Family Construction) | Residential Building Permit (New Single-Family Construction) → |
| Walsh | $15.00Verifiedvia Building Permit (Structures, Carports, Fences, and Other Construction) | Building Permit (Structures, Carports, Fences, and Other Construction) → |
| Wellington | $25 flatVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Westcliffe | $100.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Westminster | Varies by valuation — see Residential Building Permit fee tiersVerified | Accessory Dwelling Unit (ADU) Permit → |
| Wheat Ridge | $26.50 minimum, scaling per the valuation tiers in the Permit Fee ScheduleVerified | Accessory Dwelling Unit (ADU) Permit → |
| Windsor | Per the Town of Windsor Fee Schedule (Code Section 14-2-100)Verified | Accessory Dwelling Unit (ADU) Permit → |
| Winter Park | $54.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Yuma | $100.00Verifiedvia Building Permit (New Construction, Addition, Alteration, Repair) | Building Permit (New Construction, Addition, Alteration, Repair) → |