ADUs are having a moment in Denver, but the move to allow them citywide didn’t happen overnight. The rules homeowners see today were shaped over years of planning, public outreach, and hands-on input from people working directly with homeowners, architects, and the city.
One of those people was our very own Sarah Senderhauf, Sales Director at L&D Construction, who served for a year on Denver’s ADU Advisory Committee. The committee was formed to evaluate what wasn’t working in the existing zoning code and to recommend practical changes that would make ADUs more feasible without losing sight of neighborhood compatibility.
How did Denver get here? Why were these changes necessary? Read on to get the answers and learn the five ADU zoning updates that have made the biggest difference on the ground.
The Long Road to Citywide ADUs
In 2019, the City of Denver adopted Blueprint Denver, a 20-year vision for land use, growth, and housing. One of the key goals of Blueprint Denver was to expand housing options across the city, particularly “missing middle” housing like ADUs.
As part of that effort, the city formed an ADU Advisory Committee in 2022, made up of stakeholders who worked through public outreach, meetings, and policy discussions to identify what wasn’t working in the existing ADU zoning code and what needed to change. L&D Sales Director, Sarah, served on that committee for a year and saw firsthand how much effort went into removing barriers while still being thoughtful about neighborhood compatibility.
In July 2023, Denver City Council adopted significant updates to the ADU zoning code, which officially went into effect on July 5, 2023. These changes laid the groundwork for an even bigger step: allowing ADUs throughout the entire city, which became official on December 16, 2024. The zoning code needed to be updated first—before citywide ADUs could realistically work.
Then, in a major win for Colorado homeowners, HB24-1152 went into effect on June 30, 2025, opening up ADUs across much of the Front Range and even in Grand Junction. This marked a turning point for ADU development statewide.
Why These Changes Matter
When we first started building ADUs in Denver, figuring out where you could build one was incredibly confusing. The zoning map looked like a checkerboard, and even professionals had to dig deep to determine whether an ADU was allowed on a given lot.
Today, the rules are clearer, more consistent, and far more homeowner-friendly. Here are the five zoning changes that have had the biggest impact:
Five ADU Zoning Changes That Changed Everything
1. ADUs Are Now Allowed Throughout All of Denver
This was huge. Previously, ADU eligibility depended on specific zoning districts scattered throughout the city. Homeowners were often surprised to learn they couldn’t build simply because their property fell on the “wrong” side of a zoning line.
Allowing ADUs citywide removed that uncertainty and made the process far more equitable and predictable.
2. Minimum Lot Size Requirements Were Removed
Even if you were in a zone that allowed ADUs, minimum lot size rules often stopped projects before they started. If your lot didn’t meet the size requirement, you were forced into a costly and uncertain variance process.
Removing minimum lot size requirements eliminated one of the biggest barriers to ADU development and opened the door for many homeowners on standard Denver lots.
3. The 1.5-Story Rule Was Eliminated
For years, ADUs were limited to 1.5 stories, which led to some awkward designs across the city. The upper level could only be 75% of the footprint below it, often forcing people to build oversized garages just to get functional living space above.
Now, ADUs can be a true two stories. That means if you build a 650-square-foot garage, you can also have 650 square feet of living space above it, without design gymnastics. The result is better layouts, more usable space, and ADUs that feel like real homes.
4. Dormers Can Extend Beyond the Bulk Plane
Dormers make a huge difference inside an ADU. They add head height, natural light, and usable square footage, especially on the second floor.
Allowing dormers to extend beyond the bulk plane has dramatically improved interior livability. Combined with changes to the bulk plane on smaller lots (particularly Denver’s common 25-foot-wide lots), this update has made ADUs far more comfortable and practical.
5. ADUs Can Be Built at the South Setback
This change actually happened earlier, but it’s worth calling out because of its impact. When ADUs were reintroduced in Denver around 2010, they had to be set back 3–5 feet from the south property line to prevent shading neighboring yards.
Once ADUs were actually built, the city realized this requirement didn’t meaningfully protect neighbors—but it did limit design flexibility. Allowing ADUs to sit at the south setback opened up more usable space and better site planning.
What This Means for Homeowners Now
The rules governing ADUs in Denver—and across much of Colorado—are more supportive than they’ve ever been. But experience still matters. These zoning changes didn’t just make ADUs easier; they made good ADUs possible.
Understanding how to navigate zoning, permitting, design, and construction together is what turns these policy wins into successful projects.
If you’re considering an ADU, the most important step is still an early feasibility conversation—before plans are drawn or budgets are set. The rules may be clearer now, but the right approach is what makes the difference.
If you’d like to learn more about how these changes apply to your property, or what’s possible under the current code, we’re always happy to talk.
