ADU Rules in Denver: The Complete 2026 Homeowner’s Guide

At a Glance

A quick scan if you don’t have time for the full guide:

Denver is a Subject Jurisdiction under HB24-1152 (effective June 30, 2025), with local implementation through CB24-1303 (effective December 16, 2024).
ADUs are now permitted in every zone that allows a single-family dwelling. No minimum lot size required.
Owner-occupancy is not required for any ADU rental use.
Parking is not required for the ADU itself. Garage conversions that remove existing primary-residence parking trigger a separate compensation rule.
Size cap scales with lot size. Maximum 1,000 sq ft detached on lots over 7,000 sq ft. Smaller lots scale down.
Bulk-plane geometry governs ADU placement and height. Detached ADUs sit in the rear 35% of the lot, max 24 ft height, max 1.5 stories.
Short-term rentals are licensed but require the property to be the host’s primary residence. Pure-investment STR isn’t an option in Denver.
Denver Water charges a separate ADU System Development Charge of $2,055 (inside Denver) or $2,870 (outside) through June 30, 2026, stepping up to $2,170 / $3,030 on July 1, 2026.
Realistic permit timeline: 4 to 7 months from application to issued permit.
Administrative review only. No public hearing for a code-compliant ADU.
Also in this series: Boulder, Fort Collins, Colorado Springs, and Broomfield ADU rules guides.

Why Denver’s ADU Rules Are Different

Three forces shape Denver’s regulatory framework, and reading them in order makes the rest of the rules easier to absorb.

First, bulk-plane geometry instead of a flat sq ft cap. Most Colorado cities limit ADU size with a flat or proportional number. Denver doesn’t. The Denver Zoning Code scales the cap by lot size and uses geometric envelopes (bulk plane, rear 35% placement) to define what fits where. Reading Denver’s rules without understanding this is like trying to follow a recipe without knowing the unit of measurement.

Second, STR is licensed but tied to your primary residence. Denver allows ADU owners to short-term rent, but only if the property is the host’s primary residence. You can live in your primary and STR the ADU, or live in the ADU and STR the primary. You cannot STR both. Pure-investment STR isn’t an option in Denver.

Third, citywide ADU access. CB24-1303 expanded ADU permission to every zone that allows a single-family dwelling. Combined with no minimum lot size and no parking requirement for ADUs themselves, Denver is structurally one of the most permissive Colorado cities on the eligibility side. The constraints are dimensional (bulk plane, rear 35% placement, lot-size-scaled cap) and operational (STR licensing).

The trade-off worth absorbing: Denver gives the most ADU eligibility (every zone, no minimum lot, no parking for the ADU). What you can actually build on a specific lot requires careful geometric analysis under the bulk-plane envelope.

Can You Build an ADU on Your Denver Lot?

Almost certainly yes, if your home is on a single-family lot in Denver.

Zone eligibility. Before CB24-1303, ADU permission was uneven across Denver zones. The ordinance expanded ADU access to every zone that permits a single-unit detached dwelling, which covers nearly all residential zones citywide. The map of where ADUs are now allowed is essentially the map of residential Denver.

No minimum lot size. CB24-1303 also eliminated minimum-lot-size requirements that previously applied to ADUs. Smaller lots that used to be excluded are now eligible, though the dimensional rules below will constrain what fits.

What governs whether your specific lot can support a given size:

Lot area (drives the size cap)
Rear-35% placement requirement
Setbacks (5 ft side, 5 ft rear minimum; front matches primary)
Bulk-plane envelope (covered below)
Lot coverage cap per zone (commonly 37.5% to 50%)

For a typical Denver bungalow lot of 5,000 to 7,500 sq ft, the rear-35% area after setbacks typically supports a single-story modular ADU between 245 and 735 sq ft. Larger lots (over 7,000 sq ft) can accommodate the maximum 1,000 sq ft detached envelope.

HB24-1152 + CB24-1303: The Two Laws That Apply

Denver’s ADU framework rests on two layers of law working in concert.

HB24-1152 (state law, effective June 30, 2025). Colorado’s state ADU law applies to Subject Jurisdictions, which includes Denver. The law sets a floor for ADU permissiveness: every Subject Jurisdiction must allow at least one ADU on every lot that permits a single-unit detached dwelling, must process code-compliant ADU applications administratively, and cannot impose owner-occupancy mandates, ADU-specific minimum lot size restrictions, parking minimums (with narrow exceptions), or design standards more restrictive than those applied to the primary dwelling. HOAs lost the power to outright ban ADUs.

CB24-1303 (Denver ordinance, effective December 16, 2024). Denver went further than the state minimum. CB24-1303 expanded ADU access to every single-family zone, eliminated the minimum lot size requirement, refined the bulk-plane geometry (raising the bulk plane on lots 40 ft wide or narrower from 10 ft to 12 ft to accommodate ADU build-out), and reaffirmed the existing parking exemption that Denver had layered into the code since 2010-2019.

HB24-1154 (companion bill). The sister bill to HB24-1152 created an ADU Supportive Jurisdiction grant and loan program at the state level, funded through the Department of Local Affairs. It doesn’t impose new restrictions but incentivizes jurisdictions to go further.

Practical takeaway: HB24-1152 sets the floor. CB24-1303 went further on access. Both are enforceable, with CB24-1303 controlling Denver-specific implementation. Our walks the state-law text.

Size, Setbacks, and Height: The Dimensional Rules

Size cap. Detached ADUs in Denver max out at 1,000 sq ft on lots over 7,000 sq ft. Smaller lots scale down proportionally. For attached ADUs and interior conversions, the cap functionally tracks the primary dwelling footprint.

Setbacks for detached ADUs:

Front: matches the primary structure setback
Side: 5 ft minimum
Rear: 5 ft minimum
Rear-35% placement: the ADU must sit within the rear 35% of the lot

Max height. 24 ft maximum, or 1.5 stories. Some zones allow 17 ft as single story or the full 24 ft as 1.5 story. Two-story ADUs are technically permitted but rare in modular construction and require careful siting under the bulk plane.

Lot coverage. Varies by zone. Commonly 37.5% to 50%. The ADU footprint counts against the lot coverage cap along with the primary structure and any other accessory buildings.

These are the numbers. The bulk-plane envelope (covered next) is the geometry that ties them together and determines what actually fits on a specific lot.

The Bulk-Plane Primer

Denver’s bulk plane rule is the single most-misunderstood part of Denver’s ADU framework.

What a bulk plane is. A volume restriction, not just a height restriction. Picture a slanted ceiling that starts at a fixed height above your property line and angles inward at 45 degrees. Your ADU must fit inside that imaginary envelope.

The Denver geometry:

10 ft vertical leg starting at the property line
45° inward slope upward from the top of the vertical leg
Maximum height reached at 24 ft

Narrow-lot variation. Lots 40 ft wide or narrower get a 12 ft vertical leg (raised from 10 ft via CB24-1303). The extra 2 ft helps accommodate ADU build-out on tighter lots.

What this means in practice. A single-story detached modular ADU at 12 to 14 ft of total height fits cleanly within the bulk-plane envelope on almost every Denver lot. Two-story ADUs (around 22 to 24 ft) need careful siting, especially on narrower lots, to fit within the inward-sloping geometry.

Restrictions inside the rear 35%. Rooftop decks and second-story decks are prohibited within the rear-35% placement area.

If you’re working with a builder, the bulk-plane analysis should be done before any contract gets signed. A builder who hasn’t checked the bulk plane on your specific lot is hiding a redesign in your future.

Owner-Occupancy and Parking

Two requirements that used to apply but no longer do.

Owner-occupancy: not required. CB24-1303, effective December 16, 2024, removed Denver’s owner-occupancy requirement for ADU rental. You can rent both your primary dwelling and your ADU long-term to non-owners without restriction. This puts Denver in alignment with HB24-1152’s preemption of owner-occupancy mandates.

Parking: not required for the ADU. Denver waived ADU parking minimums between 2010 and 2019, and CB24-1303 reaffirmed the exemption. You don’t need to provide off-street parking for the ADU itself.

A separate rule that catches garage conversions. This isn’t an ADU rule per se, but it’s frequently confused with one. Denver’s general parking rules require the primary residence to maintain a certain number of off-street parking spaces depending on zone. If your ADU project converts a garage that contains the primary’s required parking, you have to replace that parking elsewhere on the lot. Compensation typically costs $10K to $30K. For more on garage conversions, our walks the trade-offs.

The practical implication: a new detached ADU on a typical Denver lot doesn’t need parking. A garage-conversion ADU that eliminates the primary’s off-street parking does need a replacement pad.

Short-Term Rental Rules

Denver’s STR framework is one of the more nuanced of the five cities we cover.

Primary residence required. To hold a Denver STR license, the property must be the host’s primary residence. You can live in your primary dwelling and STR your ADU, or live in your ADU and STR your primary dwelling. You cannot hold an STR license on a property where you don’t live, and you cannot STR both your primary and your ADU.

License fees. Application fee approximately $50, annual renewal approximately $50.

One STR license per person. Denver doesn’t allow STR portfolios.

Code citation. Denver Revised Municipal Code Chapter 32-94.

Long-term rental is fully permitted. HB24-1152 + CB24-1303 protect long-term rental of both the primary and the ADU without any owner-occupancy requirement. The STR primary-residence rule only governs short-term rental (under 30 days).

Design Standards and HOAs

Design standards. Denver applies the Building Form standards of the zone the ADU sits in. Roof form, material requirements, and dimensional standards follow zone-specific rules in the Denver Zoning Code (Article 5). HB24-1152 prevents Denver from applying ADU design standards more restrictive than those applied to the primary dwelling. There is no requirement that an ADU match the primary architecturally.

HOA carve-outs. HB24-1152 voids outright HOA bans on ADUs in Subject Jurisdictions, including Denver. HOAs can still enforce aesthetic standards that apply to the primary residence. They cannot use aesthetic standards as a back-door ban.

What this means in practice:

An HOA that requires brick exteriors and grey roofs on primary residences can apply the same standards to ADUs.
An HOA that has historically denied ADU permits or written “no accessory dwellings” into the covenants cannot enforce that restriction anymore.
HOAs in single-family-zone Denver subdivisions are now bound by HB24-1152.

If your HOA is pushing back, the codified preemption is at CRS 38-33.3-106.5.

The Permit Process: Step-by-Step

Six steps from idea to issued permit.

1. Pre-application zoning verification. Free, online, takes about a week. Confirms your lot’s zone eligibility, lot-size-scaled cap, and bulk-plane geometry. Recommended before any contract or design work.

2. ePermit online submittal. Denver uses Accela for permit submission. Site plan, floor plans, elevations, structural drawings (if engineer-stamped requirements apply), IECC energy documentation, fire-access plan, and sewer/water service plan are uploaded.

3. Concurrent reviews. Five city departments review in parallel: Zoning, Building, Fire, Transportation, and Wastewater. Each can return comments requiring revisions.

4. Comment cycles. Typical projects go through 2 to 3 comment cycles. Each cycle takes 4 to 8 weeks depending on Community Planning and Development workload. Clean submittals with experienced builders often clear in fewer cycles.

5. Permit issuance. Once all departments sign off, the building permit issues. Fees are paid at this point.

6. Inspections through Certificate of Occupancy. Construction begins, with inspections at each phase.

Realistic timeline. 4 to 7 months from application to issued permit, despite the post-HB24 administrative review mandate. Denver CPD targets a 180-day maximum for residential permits in 2026. The bottleneck is CPD throughput, not the underlying process.

What You Submit and the Inspection Sequence

Application document checklist:

Site plan with existing and proposed structures plus all setback dimensions
Floor plans for the ADU
Elevations (all four sides) showing exterior materials and dimensions
Structural drawings (engineer-stamped if required by foundation type, span, or load)
IECC energy code documentation
Fire-access plan demonstrating the 150 ft hose-reach standard
Sewer/water service plan
Survey if required by zoning verification

Inspection sequence:

Footing inspection
Foundation inspection (before backfill)
Underground plumbing inspection
Rough plumbing, electrical, mechanical (separate inspections)
Framing inspection
Insulation inspection
Drywall inspection
Final building, plumbing, electrical, and mechanical (separate)
Certificate of Occupancy

Inspections are scheduled through the Accela portal. Re-inspections, if needed, cost about $100/hr.

Denver Water SDC: The Specific Fee Story

Denver Water charges a separate System Development Charge for new ADU water taps. This is the most-misunderstood fact in Denver ADU cost analysis.

The ADU SDC is much smaller than the single-family base SDC. Single-family base SDCs inside Denver in 2026 exceed $10,000 plus a per-square-foot surcharge. The ADU-specific SDC is a fraction of that because the expected demand is lower.

The 2026 ADU SDC schedule:

January 1 to June 30, 2026: $2,055 inside Denver / $2,870 outside Denver
July 1, 2026 onward: $2,170 inside Denver / $3,030 outside Denver

A 20% Water Efficiency Credit is available for qualifying installations. The schedule is reviewed every two years; the next revision lands in 2028.

Practical implication. Combined with the building permit and inspection fees, the “permits + utility tap” line on a typical Denver ADU lands at $7K to $13K, not the $30K some out-of-date guides cite.

Our walks the full Denver cost stack with the SDC in context. For broader US framing across other ADU-mature markets, the sets the national context.

Appeals and Variances

If your code-compliant ADU application gets denied, or if you need a variance from a specific code provision, you have options.

Board of Adjustment for Zoning. Denver’s BOA hears variance requests and zoning interpretations. A variance is appropriate when your project doesn’t strictly comply with a code provision but warrants relief due to hardship or unique lot conditions.

District Court Rule 106 appeals. If the BOA denies a variance, the next step is judicial review through Colorado Rule of Civil Procedure 106(a)(4).

Building Code Appeals Board. A separate board hears appeals of building code interpretations.

Most code-compliant ADU applications don’t trigger appeals. The structure exists primarily for lot-by-lot variance requests where strict compliance creates a hardship.

How Denver Compares to Other Colorado Cities

Same five Colorado cities side-by-side, with Denver in column 2. The comparison covers the four largest Colorado cities Olerra serves; for an existing overview of the three Front Range city rules side-by-side, our

offers the earlier three-city framing.

Parameter	Denver (this guide)	Boulder	Fort Collins	Colorado Springs	Broomfield
Most recent local ordinance	CB24-1303, Dec 16, 2024	Ord 8650, Mar 8, 2025	Ord 009, 2025, Feb 14, 2025	Ord #25-45, Apr 8 / Jun 30, 2025	Ord 2265, Sept 16, 2025
Owner-occupancy	Not required	Not required	Not required	Not required for operation; affidavit at permit	Not required (Ord 2265)
Parking	None required for ADU	None required	None required	None required	Conditional (3 spaces in narrow cases)
STR rules	Primary residence required for STR license	Pre-Feb 1, 2019 STR license required	New ADUs (post-Jan 1, 2024) prohibited from STR	Prohibited on ADU properties (post-Jun 30, 2025)	Principal residence required for STR
Size cap	1,000 sq ft max detached (lot > 7,000); scales down	800 / 1,000 affordable detached	1,000 sq ft max	1,250 or 50% of primary	800 sq ft or 50% of footprint; 500 floor
Detached fire sprinkler	No	Yes ($8K to $15K)	No	No	No
Separate water tap / SDC	Required ($2,055-$3,030 ADU SDC)	Shared with primary	Depends on water provider	CSU case-by-case	Shared with primary (no separate tap)
Public notice	No	No	No	Yes (14-day posting)	No
Typical permit timeline	4 to 7 months	2 to 3 months	3 to 6 months	6 to 12 weeks	6 to 12 weeks
WUI / wildfire restrictions	None affecting ADUs	Ignition-resistant in foothills	Ignition-resistant in foothills	WUI-O: integrated ADUs only	None affecting ADUs

What the table shows. Denver has the broadest eligibility (every zone, no minimum lot, no parking for the ADU) and the slowest permit calendar of the four cities. The Denver-unique cost line is the ADU SDC. The Denver-unique constraint is bulk-plane geometry.

For the cost-focused view of the same data, see our .

FAQ

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

Building permit and inspection fees typically run $500 to $5,000 depending on project valuation. Plus the Denver Water ADU SDC ($2,055 to $3,030 in 2026). Combined permits + utility tap usually lands at $7K to $13K. The total project cost for a typical 490 sq ft detached modular ADU in Denver runs $245K to $285K all-in.

Do I need owner-occupancy to rent out my Denver ADU?

No. CB24-1303 removed Denver’s owner-occupancy requirement effective December 16, 2024. You can rent both your primary dwelling and your ADU to non-owners long-term.

Can I Airbnb my Denver ADU?

Yes, but only if you live on the property as your primary residence. Denver’s STR license requires owner-occupancy: you can live in your primary and STR your ADU, or live in your ADU and STR your primary, but you cannot STR both.

What is the Denver bulk-plane rule?

A volume restriction that requires your ADU to fit inside a slanted envelope starting 10 ft above the property line (12 ft on lots 40 ft wide or narrower) and sloping inward at 45 degrees up to a maximum of 24 ft. Single-story modular units almost always fit. Two-story units require careful siting.

How big can my Denver ADU be?

Detached ADUs max out at 1,000 sq ft on lots over 7,000 sq ft. Smaller lots scale down proportionally. Most typical Denver bungalow lots support 245 to 735 sq ft units in the rear 35% after setbacks and bulk-plane analysis.

How long does a Denver ADU permit take?

Realistically 4 to 7 months from application to issued permit. Denver Community Planning and Development targets a 180-day maximum for residential permits in 2026, but throughput backlog often pushes that.

What’s CB24-1303?

Denver’s local ordinance implementing HB24-1152. Effective December 16, 2024. Expanded ADU access to every zone allowing single-family dwellings, eliminated the minimum lot size, removed owner-occupancy, and reaffirmed parking exemptions.

Can my HOA stop me from building an ADU?

No. HB24-1152 voided HOA outright bans on ADUs in Subject Jurisdictions, including Denver. HOAs can still apply aesthetic standards if those standards apply to the primary residence already. The codified preemption is at CRS 38-33.3-106.5.

Are there grants or incentives for Denver ADUs?

The state’s Colorado ADU Grant Program (ADUG) opens its next funding window February 2 to March 18, 2026. Denver’s West Denver Single Family + ADU Pilot Program offers pre-approved plans and financing assistance for owners committing to affordable rental terms.

How Olerra Builds in Denver

We build detached modular Flex Flat ADUs across the Front Range, Denver included, on a fixed-price contract. Once you sign, the unit price, foundation, site work, utility hookups, Denver Water tap, permits, and install are locked. No change orders unless excavation reveals something truly unforeseen, and even then we walk you through the change before it happens.

Our property check confirms what your specific Denver lot allows under bulk-plane, setback, rear-35%, and zone-specific rules before any contract gets written. Our walks the full five-step sequence from property check to keys, typically 3 to 6 months from contract signing.

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Notes from Denver projects

Practical things that save time and money on a Denver ADU project, learned from doing this on actual lots.

Verify your water service provider before you design. Denver Water covers most of the city, but properties at the edges (parts of Glendale, north of I-70 in Adams County) may be on different utilities. The ADU SDC numbers in this guide are Denver Water’s specifically. Confirm yours at denverwater.org before you budget.

Get the bulk-plane analysis before contract, not during plan review. On narrow lots especially, the bulk-plane geometry can rule out a unit size you’d assumed would fit. A builder who hasn’t done the bulk-plane fit-check on your specific lot is hiding a redesign in your future.

Apply for Denver Water service before July 1, 2026 to lock the lower SDC rate. The schedule steps up on July 1: $2,055 to $2,170 inside Denver, $2,870 to $3,030 outside. If you’re close to the deadline, a few weeks of timing matters.

For garage conversions, get the parking-compensation cost itemized in the original quote. Garage conversions that remove existing primary-residence parking trigger a $10K to $30K compensation cost. Some quotes hide this until the change-order stage. Insist on it being a named line at contract signing.

Historic district properties add 2 to 4 months and $5K to $15K. Wash Park, Capitol Hill, Cherry Creek, and Country Club have Landmark Preservation Commission review. The process is still administrative under HB24-1152 but the design-review layer adds calendar and design adjustments. Confirm your lot’s overlay status before committing to a contract.

Bundle your IECC energy compliance documentation with the original permit submittal. Plan reviewers often catch missing energy code documentation late in the cycle, which kicks the project back through another 4-to-8-week comment round. Submit it the first time and the cycle compresses.

Check the West Denver SF+ ADU Pilot if you’re considering long-term affordable rental. Pre-approved plans and financing assistance are available through the Denver Housing Authority and Habitat for Humanity of Metro Denver partnership in exchange for long-term affordable rent commitments. Worth checking eligibility before designing.

The Colorado ADU Grant Program (ADUG) opens February 2 to March 18, 2026. State-level pass-through funding administered by the Department of Local Affairs. Worth checking eligibility if your project timeline allows you to apply during the window.

Talk to a Builder Who Knows Denver Rules

The fastest way to move from rules-reading to a real build is a property check on your specific lot. Zone eligibility, lot-size-scaled cap, bulk-plane fit, rear-35% placement, and Denver Water service area all shape what’s actually buildable.

No spec house. No long sales call. A real number based on your real Denver lot.

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Sources

1. Colorado General Assembly. .

2. City and County of Denver. .

3. City and County of Denver. .

4. Denver Water. .

5. City and County of Denver. .

6. ArcWest Architects. .