A Homeowner's Guide to Denver ADU Rules (2026)

Backyard cottages, garage conversions, and basement apartments — known as accessory dwelling units, or ADUs — have become an increasingly popular option for Denver homeowners. Whether the goal is to house a family member, earn rental income, or add long-term flexibility to a property, an ADU can be a practical alternative to moving or purchasing a second lot.

Before committing to a project, it helps to understand what the rules actually allow. Below is a plain-language summary of Denver's ADU framework as it stands in 2026.

As of recent zoning changes effective December 2023 and Colorado state law HB 24-1152, Denver now allows ADUs in every residential zone that permits a single-family home. That covers roughly 70 percent of Denver land — up from about 36 percent before the change. There is no minimum lot size requirement for an ADU, which means the rule applies to a wide range of properties across the city.

Detached ADUs are capped at 1,000 square feet on lots over 7,000 square feet. Smaller lots scale down proportionally. The maximum height is 24 feet, or one and a half stories.

Placement also matters. A detached ADU must sit within the rear 35 percent of the lot, with a minimum five-foot rear setback. These rules shape not just how large the unit can be, but where on the property it can actually go.

Owner-occupancy is not required for long-term ADU rentals of 30 days or more as of June 30, 2025. That means a homeowner can rent the ADU independently without living on the property themselves.

Short-term rentals under 30 days are different. They require a short-term rental license, and the owner must live on the property as their primary residence.

Parking is generally not required for the ADU itself. The one exception: if you are converting an existing garage into an ADU and that conversion removes parking, a separate rule may be triggered.

Homeowners associations can no longer outright ban ADUs, though they may apply the same aesthetic standards to an ADU that they apply to the primary home.

The most misunderstood and constraining part of Denver's framework is the bulk plane envelope. It governs how tall an ADU can be and where it can sit on the lot, and it ultimately determines what actually fits on a given property. Because the bulk plane is specific to each lot's dimensions and geometry, it is difficult to evaluate without a professional design analysis.

Understanding what is allowed on paper is different from understanding what will actually fit on your specific lot. Producing permit-ready drawings and analyzing what fits under the bulk plane envelope is the design work we do at Creating Design Solutions.

We start with a site-specific analysis of your lot geometry, then develop schematic options that work within Denver's ADU framework. From there, we produce a complete construction drawing set that can be submitted for permit — including floor plans, elevations, sections, and the code-compliance documentation the city requires.

If you are considering an ADU on your Denver property, the first step is understanding what the rules allow and what your lot can accommodate. Book a consultation with Creating Design Solutions and we will walk through your specific situation, your goals, and what a realistic path to permit looks like.

ADU rules change frequently. Homeowners should verify current code with the City of Denver before making decisions.