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Accessory dwelling unit companies — St. Louis, MO

Looking for accessory dwelling unit companies in St. Louis, MO? Call AccessoryDwellingUnit Pros for a contact a provider — no obligation. Licensed adu builders serve St. Louis and the surrounding area, and you'll get straight answers on timing and what affects the price.

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

Frequently asked in St. Louis

What are the disadvantages of ADUs?
How much does an ADU cost in Missouri?
What are the rules for ADUs in St. Louis?
Is an ADU allowed in St. Louis?

Yes, accessory dwelling units are permitted in St. Louis, provided they meet the city's zoning and building code requirements. These regulations typically cover aspects such as minimum lot size, occupancy limits, and design standards. Local professionals will ensure your project adheres to all these rules.

What is a typical ADU size for St. Louis?

Typical ADU sizes in St. Louis can range from compact studios around 300-400 square feet to larger units of 600-800 square feet, depending on your needs and lot. The professionals will help determine the optimal size based on your property and city ordinances. Call for a personalized assessment.

How long does it take to build an ADU in St. Louis?

The construction timeline for an ADU in St. Louis can vary, generally taking between 3 to 6 months, depending on permitting, the complexity of the design, and material availability. Early consultation with experienced builders can provide a more accurate projection for your specific project.

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

281,754residents
4,565per sq mile
—ZIP codes served

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

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