800 Sq Ft ADU Cost in Denver, CO
A 800 sq ft ADU in Denver, CO costs roughly $299,000–$517,000 all-in for 2026, including permits, utilities, and soft costs. Adjust the slider to see other sizes.
Cost Breakdown (Mid-Range)
| Category | Amount | Share of Mid Total |
|---|---|---|
| Hard construction (labor + materials) | $328,000 | 84% |
| Soft costs (design, engineering, PM) | $39,360 | 10% |
| Permit and impact fees | $12,000 | 3% |
| Utility hookups | $9,000 | 2% |
| Mid-range total | $388,360 | 100% |
Last updated April 2026.
Building a 800 Sq Ft ADU in Denver: What's Specific Here
Denver only opened ADUs to all single-family zones in 2023 (Expanding Housing Affordability text amendment), and demand has pushed plan review to 10-18 weeks. The hidden cost in Denver is the 36-inch frost depth — every foundation footing has to go below frost line, which means an extra $2,500-$5,000 in concrete and labor versus the warm-climate norm. Detached ADUs also commonly require a separate water tap from Denver Water unless the existing meter is sized up. For a 800 sq ft build specifically, expect 10-18-week plan review through Denver Community Planning and Development (CPD) and a build sequence shaped by the city's cold, semi-arid climate and Denver Zoning Code Article 11, IRC with Denver amendments, frost depth 36" requirements.
What a 800 Sq Ft ADU Actually Gets You
At 800 sq ft you can fit a generous 1-bed or tight 2-bed. Denver Water tap upsizing becomes more likely, adding $4,000-$8,000. Lot coverage starts to bind on smaller Capitol Hill or Highland lots under 5,500 sq ft.
Cost by Build Method
| Build method | Low | Mid | High | Notes |
|---|---|---|---|---|
| Stick-built (custom) | $299,306 | $388,360 | $517,414 | Most common path; highest cost, most layout flexibility |
| Prefab / panelized | $263,389 | $357,291 | $496,717 | 15-25% faster, 5-10% cheaper; limited layout options |
| Modular (factory-built) | $269,375 | $368,942 | $517,414 | 20-30% faster install; needs crane access on site |
| Garage conversion | $164,618 | $240,783 | $372,538 | Only if existing garage is at least 800 sq ft; lowest-cost route |
Realistic Build Timeline for 800 Sq Ft in Denver
| Milestone | Typical duration |
|---|---|
| Design + construction documents | 4-8 weeks |
| Denver, CO permit submission + review | 10-18 weeks |
| Site prep + foundation | 3-4 weeks |
| Framing + rough-ins (MEP) | 6-9 weeks |
| Finishes + final inspection | 8-11 weeks |
| TOTAL (design → certificate of occupancy) | 31-50 weeks |
Financing a $388,000 800 sq ft ADU in Denver, CO
Most Denver, CO homeowners stack a cash or HELOC down payment with a construction-to-perm loan. Sample scenario for a mid-range 800 sq ft build:
| Total project cost (mid) | $388,360 |
| 20% down payment (cash or HELOC) | $77,672 |
| Loan principal (80%) | $310,688 |
| Estimated rate (May 2026) | 7.5% (30-year) |
| Estimated monthly payment | $2,715 |
| Estimated rent (800 sq ft in Denver, CO) | $1,388–$2,400/mo |
| Break-even rent target | $2,715/mo |
Sample scenario only — your actual rate, term, and rent will vary. Use the loan calculator to plug in your numbers.
Denver Permit Fee Detail
| Plan check | $800–$2,000 |
| Building permit | $1,500–$3,500 |
| Impact fees | $2,000–$6,000 |
| School fees | N/A |
| Utility hookups | $2,000–$5,000 |
Questions to Ask Denver ADU Contractors
Before signing with a contractor for your 800 sq ft ADU in Denver, CO, ask:
- How many full 1- and 2-bedroom ADUs have you completed in Denver in the last 24 months?
- What's your average permit timeline with Denver Community Planning and Development, and how do you handle plan-check correction cycles?
- Do you handle 36-inch frost footings and Denver Water tap-size review in-house or sub it out?
- What's specifically included vs. excluded in your turnkey quote — soft costs, utility tap fees, landscaping, driveway repair?
- What's your payment schedule, and what triggers a change order vs. an allowance overrun?
- Can you provide addresses for 2-3 completed Denver ADU projects I can drive by?
How We Calculate This
These are 2026 all-in market estimates. Hard costs scale linearly with square footage using a low/mid/high per-sq-ft band calibrated to recent build data in each metro. Soft costs (design, engineering, project management) are applied at ~12% of hard costs. Permit and utility hookup fees are set to local base amounts and lightly adjusted for size. For an itemized estimate tied to your lot, finish level, and specific city jurisdiction, use our Cost Estimator.
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Frequently Asked Questions
How much does a 800 sq ft ADU cost in Denver, CO?
A 800 sq ft ADU in Denver, CO typically costs $299,000–$517,000 all-in for 2026. The mid-range estimate is $388,000, which includes hard construction ($328,000), soft costs ($39,360), permit fees ($12,000), and utility hookups ($9,000).
What is the price per square foot for ADUs in Denver, CO?
For a 800 sq ft build in Denver, CO, expect $374–$647/sq ft all-in. The mid-range is roughly $485/sq ft. Per-sq-ft cost falls slightly at larger sizes because permit and utility fees amortize over more square footage.
How long does a 800 sq ft ADU take to build in Denver, CO?
Total timeline runs 31-50 weeks from design start to certificate of occupancy in Denver, CO. Permits alone take 10-18 weeks through Denver Community Planning and Development (CPD), followed by 17+ weeks of construction. Pre-approved plans and prefab paths can shorten the permit phase.
Can I finance a $388,000 ADU in Denver, CO?
Yes. For a $388,000 mid-range build, common options are construction-to-permanent loans, HELOC, cash-out refinance, or RenoFi. At current ~7.5% rates, a fully-financed build is roughly $2,715/month on a 30-year term. Use the ADU loan calculator to compare products side by side.
What size of ADU is allowed in Denver, CO?
Denver, CO permits detached ADUs up to 1000 sq ft on most lots. A 800 sq ft unit is within the typical limit, so the standard ADU permit path applies.
What rent can I expect from a 800 sq ft ADU in Denver, CO?
In Denver, CO, 800 sq ft ADUs rent for approximately $1,388–$2,400/month based on 2026 market rents for comparable units. Newer construction with separate parking and a private entrance lands at the high end of that range.
What's the difference between a 800 sq ft and a 1000 sq ft ADU in Denver, CO?
A 800 sq ft Denver, CO ADU comes in around $388,000 mid-range, while the next bucket up at 1000 sq ft runs about $481,000 — roughly $93,000 more. The bigger size adds a bedroom or larger living area but still falls within the city ADU size cap.
What's the most common mistake when building a 800 sq ft ADU in Denver, CO?
Underestimating the 36-inch frost footings and denver water tap-size review requirement — many homeowners get bids from contractors who don't price these into the quote, then face change orders mid-build. Always confirm in writing how 36-inch frost footings and denver water tap-size review is handled before signing.
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