Adu services — St. Louis, MO

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 services simplify the complex process of turning unused yard space into a functional, independent living unit. This involves architectural drafting, structural engineering, and managing municipal building departments to secure necessary approvals. You should look for these services when you are ready to expand your home’s footprint for rental income, guest accommodations, or multi-generational living. Engaging experts ensures the project stays compliant with state codes while meeting your specific design goals for a secondary dwelling.

Frequently asked in St. Louis

Also serving nearby: O Fallon · Springfield · Columbia · Champaign · Peoria

All cities in Missouri →

More on this: HUD ADU resources — ADU policy and financing research.

Service area details

Serving all of St. Louis — population 281,754; about 4,565 residents per square mile across 61.7 sq mi.

Neighborhoods served in St. Louis: Lafayette Square, Tower Grove, The Hill, Benton Park, Soulard — and every surrounding area.