Can you build a PSL Modular unit in Missouri?

The Missouri Public Service Commission (PSC), through its Manufactured Housing and Modular Units program — an unusual arrangement (most states use a building or labor department). Each modular unit must bear a PSC seal of compliance; selling or installing a unit without one is a misdemeanor. Models built after November 30, 2024 are constructed to the 2021 IBC. With the seal, your local jurisdiction permits the site work without re-reviewing the structure.

Yes, both allow them with different rules. The City of St. Louis amended its zoning code to permit ADUs in all districts that allow residential use. Kansas City allows ADUs in specific zoning districts through a conditional use permit. Columbia has streamlined ADU permitting. There's no statewide law, so confirm your specific city's process.

No. ADUs are governed locally, so rules vary widely between cities and counties. St. Louis is among the most permissive (all residential-allowing districts); other cities require conditional approvals or restrict ADUs to certain zones. Confirm your jurisdiction before designing.

Wind and seismic. Missouri sees significant tornado/high-wind activity statewide, so the structure is engineered to the design wind speeds. And the Bootheel (far southeastern Missouri) sits squarely in the New Madrid Seismic Zone — one of the most significant seismic risk areas in the central US — so seismic design is essential there. PSL Modular sets the spec from your site.

Yes. St. Louis and Kansas City rental demand plus regional workforce needs suit modular, and St. Louis's broad ADU allowance makes backyard units attractive. The PSC-sealed unit clears the building; your work is the local zoning and site.