ADU Locator

1 Best ADU Builders in Boulder, Colorado

Verified ADU contractors and builders in Boulder, CO

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Petra Custom Builders

Specializing in garage-to-living-space conversions throughout the Boulder area, this contractor transforms underutilized garages into functional bedrooms, home offices, and recreational spaces with expert craftsmanship and attention to detail. Whether you're looking to add square footage or create a dedicated workspace, they deliver custom solutions tailored to your home and lifestyle needs.

+1 720-291-7918
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Frequently Asked Questions — ADU Builders in Boulder

How much does it cost to hire an ADU builder in Boulder?

ADU construction costs in Boulder, Colorado vary widely depending on size, type, and site conditions. Detached ADUs typically range from $150,000–$400,000+, while garage conversions and attached ADUs can be more affordable. Contact multiple builders in Boulder to get accurate quotes for your specific project.

How long does it take to build an ADU in Boulder?

In Boulder, the ADU construction timeline typically ranges from 6 to 18 months from permit application to move-in. Permitting alone can take 2–6 months depending on Colorado local regulations. Prefab and modular ADUs often have faster timelines than site-built units.

Do I need a permit to build an ADU in Boulder?

Yes, a building permit is required for ADU construction in Boulder, Colorado. Your ADU builder will typically handle the permit application as part of their service. Colorado has adopted streamlined ADU permitting laws in recent years, which may reduce wait times.

What types of ADUs can be built in Boulder?

Common ADU types in Boulder include detached ADUs (backyard cottages), attached ADUs, garage conversions, basement conversions, and prefab/modular ADUs. The best type for your property depends on lot size, zoning, and budget. A local Boulder ADU builder can advise on what's allowed on your specific parcel.