Skip to main content

Oregon State Flag An official website of the State of Oregon »

Prefabricated Structures Program

The Building Codes Division administers a statewide Prefabricated Structures Program. “Prefabricated structures” are also known as “modular buildings” in other states. The Prefabricated Structures Program regulates the design and construction of prefabricated structures and prefabricated components constructed at an off-site location intended to be sold, leased, or installed in Oregon. Regulatory authority for the Prefabricated Structures Program is under ORS 455.705 and administrative rules adopted in OAR Chapter 918, Division 674. Prefabricated structures are designed and constructed according to Oregon adopted specialty codes.

A “prefabricated structure” as defined in ORS 455.010 means a building or subassembly that has been in whole or substantial part manufactured or assembled using closed construction at an off-site location to be wholly or partially assembled on-site. A prefabricated structure does not mean a “manufactured dwelling” (a dwelling built to federal HUD standards) as defined in ORS 446.003, or a “small home” (400 square feet or less built to a residential code) as defined in ORS 455.616 (referenced as “Section 2, Chapter 401, Oregon Laws 2019” or House Bill 2423 (2019)).

“Closed Construction” as defined in OAR 918-674-0005 means a factory-assembled structure or component that encloses factory-installed structural, mechanical, electrical, plumbing or energy conservation equipment or material inside a floor, wall, or roof cavity which is not entirely open for visual inspection of the equipment or material at the site.

Get detailed information for businesses constructing prefabricated structures or components through the links below. This information is subject to change as laws, rules, codes, or other requirements change. Please contact Prefabricated Structures Program staff if you have questions or need further information.