Grannio

Can You Build an ADU in Boulder?

Yes — Boulder is governed by Colorado's statewide ADU law, which limits what the city can restrict. A 700 sq ft detached ADU here runs about $181,000–$296,500.

Construction in Boulder runs about 12% above the Colorado average, so budget toward the higher end of these ranges.

Detached ADU (700 sq ft)

$181,000–$296,500

Garage conversion (400 sq ft)

$56,500–$103,500

Statewide protection

Yes

What applies in Boulder

Colorado's HB24-1152 (2024) requires larger municipalities in metropolitan areas to allow ADUs in single-family zones, phasing in by-right approval.

Because Colorado has a statewide ADU law (Colorado HB24-1152 (2024)), Boulder must follow these minimums even where its older zoning code is stricter. Confirm fees and design standards with the Boulder planning department.

Estimate your Boulder ADU cost

Your property

ADU type

Estimated cost in Colorado

$181,000 – $296,500

≈ $259–$423/sq ft turnkey · midpoint $239,000

$162,500
Construction
$43,000
Design & permits
$33,500
Site work
Good news — building an ADU in Colorado is very likely allowed.
  • iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
  • ✓No extra parking likely required. Set by local ordinance — commonly 1 space per ADU unless near transit.
  • iOwner-occupancy varies. Owner-occupancy rules are set locally in this state.
  • ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.

Rule basis: Colorado HB24-1152 (2024)

If you rent it out

$1,125–$1,825

est. rent/mo

7.4%

gross yield

14.5 yrs

payback

~$16,461/yr after a 7% vacancy allowance, before financing & maintenance.

Financed over 20 yrs at 7.5%, the build is about $1,925/mo — vs ~$1,475/mo in estimated rent.

Get your detailed feasibility report →

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.

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Other Colorado cities

DenverColorado SpringsAuroraFort CollinsLakewood

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.