AGrannio

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 statewide standard (Colorado HB24-1152 (2024)) is the starting point, but parcel-level rules, fees and design review are set locally. Confirm those details with Boulder before design.

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.