Cost to build accessory dwelling unit — Boulder, CO
Last updated: September 24, 2026
What affects the price
Building an ADU involves variables that shift your total investment. The footprint size and complexity of the architectural design are primary factors. Are you planning a detached unit that requires new utility trenching, or is this a garage conversion that uses existing plumbing? Site accessibility, soil conditions, and your choice of finishes—like luxury flooring versus standard options—also play significant roles. Permitting fees vary widely depending on your local municipality and current zoning requirements. Exact pricing confirmed free on the call.
About this service
The expense of building an ADU varies based on site preparation, whether you need to run new sewer or electrical lines, and the level of interior customization you choose. Larger custom builds naturally require more materials and labor than simpler conversions. We provide exact pricing confirmed free on the call.
Frequently asked in Boulder
What prefab ADUs are available in Boulder?
When might I need an emergency ADU in Boulder?
What's the permit cost for an ADU in Boulder?
What does 'accessory dwelling unit' mean for my home?
An accessory dwelling unit (ADU) means adding a second, smaller living space to your property. It’s like a mini-house on your lot. It has its own kitchen, bathroom, and entrance. ADUs provide extra space for family, guests, or renters. They increase your home's overall utility.
Are there ADU homes in Boulder?
Yes, accessory dwelling unit (ADU) homes are becoming more common in Boulder. These are properties with a secondary, independent living space. This unit has its own kitchen, bathroom, and bedroom. They offer flexibility for family or renters. They add value and utility.
What's the best accessory dwelling unit for my property?
Who are ADU contractors in Boulder?
Also serving nearby: Longmont · Westminster · Arvada · Thornton · Lakewood
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of Boulder — population 105,898; about 3,937 residents per square mile across 26.9 sq mi. ZIP codes covered include 80301, 80302, 80303, 80304, 80305, 80306, 80307, 80308.
Neighborhoods served in Boulder: Mapleton Hill, Newlands, Chautauqua, University Hill, Whittier — and every surrounding area.
Areas we serve
Browse by state, then city.