Adu estimate — 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

An ADU estimate is a preliminary assessment used to give you a rough idea of what your project might cost before you commit to a full design plan. This is helpful when you are in the early research phase and trying to determine if your budget aligns with your vision. Because site preparation and permit fees vary, your final cost will depend on these specifics. We provide these figures to help you plan your finances. Exact pricing confirmed free on the call.

Frequently asked in Longmont

Also serving nearby: Boulder · Thornton · Westminster · Arvada · Greeley

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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: Old Town Longmont, The Peaks, Heritage Village, Boulder County Estates, Plaza — and every surrounding area.