How Much Does an ADU Cost in South Denver? (2026)
An accessory dwelling unit in South Denver can cost anywhere from about $40,000 for a simple garage conversion to $350,000 or more for a detached new build. That is a huge spread, so here is how the ranges break down by ADU type in 2026, what moves the number, and how zoning and permits work in our area.
ADU price ranges by type
- Basement conversion: roughly $40,000-$100,000+. Finishing runs about $50-$100 per square foot, then a kitchen, separate entrance, egress, and fire separation push a true ADU toward the top of the range.
- Garage conversion: roughly $40,000-$140,000 ($50-$200 per square foot) depending on garage size and finishes. If the conversion removes required off-street parking, replacing it can add another $10,000-$30,000.
- Detached ADU: roughly $245,000-$350,000+ all-in for a one-bedroom unit, including foundation, shell, utility connections, design, and permits.
Across all types, most South Denver ADU projects land somewhere between $80,000 and $350,000.
What drives ADU cost
- Kitchens and bathrooms - the most expensive square footage in any ADU.
- Utility connections - new or upsized water, sewer, and electrical service, especially for detached units.
- Code upgrades on conversions - ceiling height, insulation, fire separation, and egress requirements often surprise homeowners.
- Detached structures - foundation, roof, and a full building shell put detached ADUs in a different cost class.
- Labor - Denver's tight trade market runs 15-25% above the national average.
Zoning and permits for South Denver ADUs
ADU rules vary by city across the south metro, and many jurisdictions now allow ADUs in some form. Plan-review timelines vary widely too: Arapahoe County first-round review currently runs about 6-8 weeks for projects under $100,000 and 10-12 weeks above that, while Douglas County offers over-the-counter review for some interior conversions. A design-build contractor researches your jurisdiction and manages permitting and inspections for you.
Is an ADU worth it?
Basement ADU conversions tend to have the best return - lower build cost against comparable rental income, with payback periods often in the 7-10 year range. Detached units cost the most but add the most flexibility and long-term property value.
Narrow your range in under a minute
A budget that could land anywhere between $40,000 and $350,000 is not much to plan around. Our free instant ballpark calculator narrows it to your project with a few quick questions - no phone call required.
Get an ADU estimate in South Denver
Custom Professional Renovations designs and builds ADUs across Englewood, Greenwood Village, Centennial, Highlands Ranch, Littleton, Lone Tree, Parker, Castle Rock, and surrounding South Denver communities, backed by a 2-year workmanship warranty. Book a free consultation or explore our ADU services.