Denver's ADU Builder — Backyard Cottages, Garage Conversions & More
303 Construction has been building in Denver's backyards since before ADU was a buzzword. Over 20 years of Denver builds. Full permit handling. One team, start to finish.
WHAT IS AN ADU?
An Accessory Dwelling Unit (ADU) is a second, self-contained living space on the same lot as your primary home. Denver City Council voted in November 2024 to allow ADUs in all residential neighborhoods — and Colorado's HB24-1152 requires every city in the metro to comply.
If you own a home anywhere in the Denver metro area, you can almost certainly build one now. ADUs can generate $1,500–$2,500/month in rental income, house family members, or simply add lasting value to your property.
ADUs come in many forms — detached backyard cottages, garage conversions, basement units, and attached additions. Each type has different costs, timelines, and requirements. 303 Construction has been building in Denver for over 20 years, and we handle everything from initial lot assessment and design through permits, construction, and final inspection — one team, one contract, one point of contact.
TYPES OF ADUs WE BUILD
Four ADU configurations to fit your property, goals, and budget.
Detached Backyard ADU
$180,000 – $350,000
A fully separate structure in your backyard. Maximum privacy and rental value. Typically 400–1,200 sq ft.
Best for: Homeowners with larger lots who want to maximize rental income or create fully independent living space for family.
Garage Conversion ADU
$80,000 – $130,000
Transform an existing detached garage into a livable space. Most cost-effective ADU option. Works best with alley access.
Best for: Properties with detached garages and alternative parking. The fastest, most affordable path to a rentable unit.
Basement ADU
$100,000 – $180,000
Convert your basement into a legal separate unit with its own entrance. Lowest disruption to your property footprint.
Best for: Homes with full unfinished basements and sufficient ceiling height. No change to your yard or exterior.
Attached Addition ADU
$150,000 – $280,000
An addition connected to your home with a private entrance. Good for homes with limited yard space.
Best for: Smaller lots where a detached unit won't fit. Ideal for multigenerational living with proximity to the main home.
THE 303 ADU BUILD PROCESS
Site and Zoning Review
We assess your specific lot, confirm ADU eligibility under your city's current zoning (every Denver metro city now allows ADUs under HB24-1152), and identify constraints before you spend a dollar.
Design and Planning
We develop your ADU design to maximize space, match your home's architecture, and meet all local building code requirements.
Permit Submission
We handle all permit applications with your city's planning department. We know what reviewers want and how to avoid the delays that trip up other builders.
Construction
Our crews build your ADU on schedule. We handle every trade — framing, electrical, plumbing, HVAC, insulation, drywall, finishes. One point of contact throughout.
Final Inspection and Handover
We walk through the completed unit with you, pass all required city inspections, and hand over the keys.
ADU INVESTMENT AND ROI
Typical Cost
$80K–$350K
Depending on type, size, and finishes
Rental Income
$1.5K–$2.5K/mo
For a well-finished Denver ADU
Timeline
9–14 months
Permitting + construction
Vacancy Rate
Extremely Low
Denver's housing shortage
WE BUILD ADUs ACROSS THE ENTIRE DENVER METRO
Click your city to learn about ADU building in your area.
FREQUENTLY ASKED QUESTIONS
Start with a Free ADU Consultation
Not sure if your lot qualifies? Not sure which ADU type makes sense for your property? That's exactly what our free consultation is for. We'll assess your property, walk through your options, and give you a straight answer — no pressure, no obligation.