Denver ADU Zoning Rules & Common Traps

If you’re searching “Are ADUs allowed in my Denver neighborhood?” — the short answer is YES. In 2025, the city of Denver enacted a slate of changes to the zoning rules governing ADUs: namely, that nearly all residential neighborhoods and other areas that did not previously allow ADUs prior to 2025 may now build them. Here are a couple of highlights from those changes: 

• Only a licensed general contractor can build ADUs in Denver. 
• Importantly for many Denverites, detached ADUs–buildings that aren’t connected to the primary home, like a basement or garage ADU— must follow design standards based on “neighborhood context” (that means no boxy eyesores!)
• Building lot coverage exemptions for vehicle parking are now extended, so building single story ADUs was made easier. 
• New height rules for ADUs—Denver now allows more flexibility to put up a 2-story ADU. But in some neighborhoods, ADUs still can’t reach above one story
• All ADUs must have rear and side setbacks.
• Zoning rules that limited conversion of garages, basements, or other structures into ADUs were eliminated. 
• ADUs may also now be added to a duplex. 
• The maximum floor area of an ADU allowed in smaller home lots was increased, so that ADUs could accommodate a family.  

Still, each ADU is different and requires it’s own careful review and planning. Key ADU zoning considerations in Denver include:

• Lot size minimums
• Maximum building height
• Bulk plane restrictions
• Rear and side setbacks
• Alley access requirements
• Owner-occupancy rules (where applicable)
• Parking standards
• Landmark or historic overlays

These aren’t deal-breakers. But they can become costly obstacles if not evaluated early. The most common mistakes homeowners make when building an ADU in Denver include assuming buildable square footage without checking bulk plane limits, setbacks or underestimating utility upgrade requirements. At Denver Custom ADU, before we ever talk about design, we start with feasibility. Your first step should be to work with a licensed professional and start checking with the city’s zoning department.