Detached accessory dwelling unit — Longmont, CO
Last updated: September 24, 2026
What affects the price
Building an ADU is a custom project, so costs vary based on your specific choices. Site conditions are the biggest factor; if your land requires significant grading, utility extensions, or foundation work, those expenses add up quickly. Choosing high-end finishes, custom cabinetry, or complex roof lines will also push the budget higher compared to a standard design. Prefabricated units often offer predictable costs, while custom site-built structures allow for more flexibility but can be harder to estimate upfront. Exact pricing confirmed free on the call.
About this service
A detached ADU is a standalone building separate from your main house, often located in the backyard. This is a great choice if you want maximum privacy for yourself or your tenants. Cost factors include foundation requirements, utility trenching, and the exterior siding materials you choose. It is a popular way to expand your usable square footage. Exact pricing confirmed free on the call.
Frequently asked in Longmont
What are the typical considerations for a prefab ADU in Longmont?
How is the cost of an accessory dwelling unit determined in Longmont?
What are the essential steps in ADU building in Longmont?
How do I get an ADU estimate for my Longmont property?
Where can I find accessory dwelling unit services near me in Longmont?
What is the permit process for an accessory dwelling unit in Longmont?
What makes a good ADU company in Longmont?
Also serving nearby: Boulder · Thornton · Westminster · Arvada · Greeley
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of Longmont — population 98,630; about 3,396 residents per square mile across 29.0 sq mi. ZIP codes covered include 80501, 80502, 80503, 80504.
Neighborhoods served in Longmont: West Longmont, South Longmont, North Longmont, Mountain View, Hygiene — and every surrounding area.
Areas we serve
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