Looking for accessory dwelling unit contractor 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

A contractor manages the trades, materials, and timeline required to complete your backyard home. You need a contractor when you have design plans ready or need a lead to coordinate electricians, plumbers, and carpenters to get the structure move-in ready. They act as your project manager, ensuring that the work is finished on schedule and adheres to the building plans filed with your local municipality. Their role is essential for keeping the construction phase organized and safe.

Frequently asked in St. Louis

What are the disadvantages of ADUs in St. Louis?

The primary drawbacks can be the initial construction cost and potential zoning restrictions specific to certain historic districts. You'll also want to consider how an ADU might affect your property taxes and insurance. However, many St. Louis homeowners find the benefits of extra rental income or space outweigh these concerns.

How much does an ADU cost in Missouri?

The cost of an ADU in Missouri varies significantly based on size, materials, and the complexity of your site. Factors like foundation work and existing utility connections play a major role. It's best to get a personalized quote from a contractor familiar with St. Louis's specific building codes. They can give you a realistic estimate.

What are the rules for ADUs in St. Louis?

Is an ADU allowed in St. Louis?

Yes, ADUs are permitted in many areas of St. Louis, provided they meet the city's zoning and building codes. The city encourages ADUs to increase housing diversity. A professional contractor can quickly assess your property's suitability and guide you through the approval process.

What is the process for getting an ADU permit in St. Louis?

The permitting process involves submitting detailed plans to the city for review, which typically includes architectural and site plans. Experienced ADU contractors in St. Louis handle this entire process for you, ensuring all documentation is accurate and submitted correctly.

What are the benefits of adding an ADU in St. Louis?

The main benefits include generating rental income, providing space for family, and increasing your property's overall value. An ADU offers flexibility and a smart investment for homeowners in St. Louis looking to maximize their living situation. It’s a valuable addition.

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

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