Can you build a PSL Modular unit in Illinois?

The Illinois Department of Public Health (IDPH) regulates modular dwellings and commercial mobile structures under the Modular Dwellings and Mobile Structures Code (Title 77, Part 880). Since 2020, an approved third-party inspection agency must review and approve the plans, and since 2005 units must be inspected at the factory by an approved agency; one- and two-family modular dwellings conform to the 2018 IRC. With that approval, your local jurisdiction permits the site work — foundation, utilities, zoning — without re-reviewing the structure.

Soon, in many areas. Chicago's revised ADU ordinance (City Council, September 2025) takes effect April 1, 2026, ending a roughly 70-year prohibition on coach houses, basement apartments, and attic conversions across much of the city. The catch: in single-family neighborhoods, the local alderperson must opt in; there's an apprenticeship requirement for contractors on coach houses; and affordability rules apply when a property has two or more ADUs. Check your ward and zoning.

No. ADUs are governed locally. Chicago's ordinance is the headline; the collar counties (DuPage, Lake, Will, Kane) and downstate municipalities set their own rules. Confirm your specific jurisdiction.

Cold and snow statewide drive the envelope and roof design. One thing to know that surprises people: far-southern Illinois, near Cairo, sits in the New Madrid Seismic Zone, so seismic design is a real factor down there. Chicago and central Illinois are wind-and-cold environments with low seismic. PSL Modular sets the spec from your site.

Yes. Logistics, manufacturing and agricultural-region labor demand make multi-unit workforce housing valuable, and modular delivers it quickly with IDPH-approved units engineered for Illinois winters.