Adu building — 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
ADU building covers the entire process of planning, permitting, and constructing a secondary home on your property. This involves drafting site plans, getting approval from your local planning department, and handling the structural work from foundation to roof. You need this service when you are ready to officially break ground on your project. Costs are driven by the complexity of the design, site preparation, and finish materials. Exact pricing confirmed free on the call.
Frequently asked in Longmont
What are the options for accessory dwelling unit financing in Longmont?
How do I find accessory dwelling unit builders in Longmont?
What is involved in an ADU estimate in Longmont?
What makes an ADU affordable in Longmont?
What is the ADU cost in Longmont?
What constitutes an affordable accessory dwelling unit in Longmont?
What is the cost to build an accessory dwelling unit 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: Prospect New Urbanist, Old Town, Mountain View, Hygiene, Southmoor Park, The Lakes — and every surrounding area.
Areas we serve
Browse by state, then city.