Denver, Colorado · Accessory Dwelling Units

Denver's backyard just got bigger. Here's the whole picture.

Every residential lot in Denver can now hold an accessory dwelling unit, a backyard cottage, garage conversion, or basement apartment. This is the independent guide to what the rules allow, what it really costs, and who builds them.

LAST VERIFIED: SEPTEMBER 2026 · SOURCES: DENVER CPD, COLORADO HB 24-1152, DENVER WATER

The short version: Denver allows one ADU on any lot zoned for a single-family home, no minimum lot size, no extra parking, and no owner-occupancy requirement for long-term rentals. Detached units are capped at 650-1,000 sq ft depending on lot size, must sit in the rear 35% of the lot, and top out at 24 feet. Permits are reviewed administratively in roughly 4-8 weeks; a typical detached build runs $150K-$300K+ all-in and takes 4-10 months of construction.

§1, START HERE

The three questions every Denver homeowner asks

Can I build one, and what's the permit process? Almost certainly yes since the citywide zoning change and Colorado's HB 24-1152. The permit guide covers eligibility, size caps by lot, setbacks, the three permits you'll need, and realistic timelines.

What will it actually cost? Real 2026 numbers: construction ranges by ADU type, Denver's permit and utility fees (including the Denver Water charge most budgets miss), and what drives a project from $150K to $350K.

Who should build it, and how do I vet them? The questions that separate ADU specialists from general remodelers, license and insurance checks that take ten minutes, and the red flags that predict a bad project.

MORE GUIDES

Project types and neighborhoods

Compare Denver ADU builders side by side · Which builder fits your situation · How to verify a contractor · Reading and comparing quotes · When a project goes wrong

Converting a garage into an ADU · Basement ADUs and separate-entrance rules · Prefab vs. site-built: the real cost comparison · ADU rules by Denver neighborhood, and how Arvada, Lakewood and Aurora differ

§2, THE MARKET

Denver ADU builders

Denver's ADU market is young and fragmented, no single company dominates, and more than a dozen firms do serious ADU work across the metro, from design-build specialists to modular and prefab companies. The builder directory lists them with what each actually does: detached builds, garage conversions, basement units, prefab, and where in the metro they work.

Featured builder, seat open

One builder. One seat. Vetted first.

Denver ADU Guide features a single sponsored builder at a time, one company that has passed our published verification checks (license, insurance, references). Sponsorship is always disclosed and never changes what the guide says about anyone else. The featured seat for Denver is currently open.

How featuring and verification work →

Denver ADU Guide is an independent publication. We are not a contractor and we don't take referral fees per lead. Featured placement is paid, disclosed sponsorship, see our methodology and disclosure policy. Rules and fees change; verify current requirements with Denver Community Planning and Development before making decisions.