Accessory dwelling unit companies — St. Louis, MO

Last updated: September 24, 2026

What affects the price

Building an ADU involves variables that shift your total investment. The footprint size and complexity of the architectural design are primary factors. Are you planning a detached unit that requires new utility trenching, or is this a garage conversion that uses existing plumbing? Site accessibility, soil conditions, and your choice of finishes—like luxury flooring versus standard options—also play significant roles. Permitting fees vary widely depending on your local municipality and current zoning requirements. Exact pricing confirmed free on the call.

About this service

ADU companies provide end-to-end solutions, often integrating design, permitting, and construction under one roof. You need to engage a company when you want a streamlined experience and want to avoid the stress of hiring separate architects and builders. These companies handle the coordination of the entire project, ensuring that every phase of development transitions smoothly while keeping you updated on the progress and budget status of your new unit.

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: O'Fallon, Springfield, Columbia, University City, Clayton — and every surrounding area.