How much does it cost to build an ADU in Denver?

In 2026, a detached ADU in Denver typically runs $150,000-$300,000+ all-in depending on size and finish; compact modular detached units around 490 sq ft commonly land in the $245,000-$285,000 range all-in. Garage conversions typically run $120,000-$200,000 and basement ADUs $80,000-$180,000. Permits plus utility charges usually add $7,000-$13,000.

What are Denver's ADU permit and utility fees?

Building permit and inspection fees typically run $500-$5,000 depending on project valuation. Denver Water charges a separate ADU System Development Charge of $2,170 inside Denver ($3,030 outside) as of July 2026. Combined permits and utility charges usually total $7,000-$13,000.

Guide · Costs

What an ADU really costs in Denver (2026)

LAST VERIFIED: AUGUST 2026 · SOURCES: DENVER CPD FEE SCHEDULES, DENVER WATER, PUBLISHED DENVER BUILDER PRICING

Direct answer: Budget $150K–$300K+ all-in for a detached ADU in Denver in 2026. Compact modular detached units (~490 sq ft) commonly land at $245K–$285K all-in; larger custom detached builds reach $350K+. Garage conversions run roughly $120K–$200K, basement ADUs $80K–$180K. On top of construction, permits plus utility charges typically add $7K–$13K — including a Denver Water System Development Charge of $2,170 (July 2026 rate, inside Denver) that many first budgets miss.

§1 — BY TYPE

Cost ranges by ADU type

DENVER ADU COST RANGES, 2026 — ALL-IN (DESIGN + PERMITS + CONSTRUCTION)
Type	Typical range	Notes
Detached, custom stick-built	$180K – $350K+	Widest range; size, foundation, and finish level drive it
Detached, modular/prefab (~490 sq ft)	$245K – $285K	More predictable pricing; site work still varies
Garage conversion	$120K – $200K	Existing shell saves structure cost; utilities and insulation dominate
Basement ADU	$80K – $180K	Cheapest entry; egress windows, ceiling height, and fire separation are the gates

Cost per square foot falls as units grow — kitchens and bathrooms cost the same in a 500 sq ft unit as an 900 sq ft one, which is why small units look expensive per foot.

§2 — FEES

Permit and utility fees

DENVER FEES & CHARGES, 2026
Item	Amount
Building permit + inspections (valuation-based)	$500 – $5,000
Denver Water ADU System Development Charge (inside Denver, from Jul 1 2026)	$2,170
Denver Water ADU SDC (outside city, from Jul 1 2026)	$3,030
SUDP, tap and connection work (site-dependent)	varies
Typical combined permits + utility total	$7,000 – $13,000

§3 — DRIVERS

What moves the total up or down

Utility runs. Distance from the main lines to the rear of the lot — trenching for water, sewer, and electrical is the classic surprise line item.
Foundation and site conditions. Slope, soil, and access for equipment in an alley lot.
Bulk-plane workarounds. Designing 1.5 stories inside the height envelope near a property line can add structural complexity.
Historic district review. Design-matching requirements add design cost and 2–4 months (see the permit guide).
Finish level. Rental-grade versus family-grade interiors swing budgets 15–25%.

§4 — RETURN

Is a Denver ADU worth it?

For long-term rental, the math is stronger than it has ever been in Denver: no owner-occupancy requirement means both units can be rented, and one-bedroom detached units in central neighborhoods command healthy long-term rents. Short-term rental is limited to primary residences under Denver's STR licensing. Beyond rent, appraisers increasingly credit permitted ADUs in valuations, and multigenerational use — housing a parent or adult child — is the reason roughly half of Denver ADU clients build. Run your own numbers against actual quotes; be skeptical of any builder marketing that promises specific rental yields.

Ranges reflect published Denver builder pricing and city/utility fee schedules as of August 2026. Every lot differs; treat these as budgeting ranges, not quotes, and verify current fees with Denver CPD and Denver Water.