Accessory dwelling unit companies — St. Louis, MO

Last updated: September 24, 2026

What affects the price

Building an ADU involves several moving parts that shape your total investment. The final figure depends heavily on whether you choose a prefab unit or a custom build from the ground up. Site conditions are another major factor; if your property requires extensive grading, utility trenching, or foundation work, costs will climb. You also have to consider your choice of finishes, like high-end appliances or custom cabinetry. Navigating local permit fees and impact assessments also adds to the total.

About this service

These companies provide comprehensive support for homeowners, often pairing design experts with construction crews to handle the entire project under one roof. They are helpful when you want to avoid hiring separate architects and builders. You should look into these companies when you want a streamlined experience and a single point of accountability for your backyard project from start to finish.

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: The Hill, Soulard, Central West End, Tower Grove, Benton Park — and every surrounding area.