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Common questions from cities and counties about manufactured homes and other mobile structures:

Q. What does a local building department need to know about modular buildings?

A. L&I inspects modular buildings that are prefabricated off site to assure compliance with the state building code. Once a building is approved, L&I sends a notification to the local building department, along with the building plans. The notification form and plans will show what needs to be done by the local inspector to complete the factory portion of the building when it is installed.

The local building department is responsible for permitting the site installation, along with approving the foundation design, utilities and the location of the structure on site. L&I approval does not take the place of any permits that may be required by the local building department.

Q. Who inspects changes or alterations to L&I approved structures?

A. L&I permits and inspects changes made to food trucks or concession trailers, mobile medical units, commercial coaches, recreational vehicles and park models. Alterations, changes and remodels of modular buildings (gold label) are only done by L&I if the building is a temporary install, such as a portable school classroom. All other buildings are permitted and inspected by the local building department and electrical inspector. Temporary worker housing alterations are inspected by the state Department of Health.

Q. How do I know if a modular structure been inspected?

A. If you locate a label (insignia of approval) you will know the structure was inspected. View the various types of labels issued by L&I, where they are typically located on a structure, and their colors.

Q. What is the “Notice to Local Enforcement Agency” (NLEA) form for?

A. If a local building department receives an NLEA form, it is because a modular building is being shipped into your jurisdiction. The form will identify the manufacturer, approximate arrival date and installation location. L&I does not inspect at building sites so the form will also list any items that were not completed at the factory and need to be inspected during installation.

Q. What do local building and fire authorities need to know about concession units at fairs and events?

A. L&I inspects trucks and trailers used for concessions for fire and electrical safety. Units that have passed inspection will have a label (insignia of approval). L&I does not regulate how concession units are operated or where they can be located. L&I does not inspect concession units operated out of tents or push carts or buildings that are constructed on site.

Q. Who inspects the installation of manufactured and mobile homes?

A. Local building departments inspect the installation of manufactured and mobile homes The local inspector needs to verify that the home is installed according to the manufacturer’s installation instructions and the L&I installation requirements contained in WAC 296-150I ( This inspection will also include items on the interior of the home, such as roof and floor beam bolting and under the floor such as pier and column blocking. Inspectors should also verify that the installer has posted their WAINS tags on the home, and if they are missing, it should be reported to the L&I installer program.

Q. Who inspects changes or alterations to manufactured and mobile homes?

A. In most cases, L&I permits and inspects changes or alterations made to manufactured and mobile homes. Structures built next to the home, such as garages, are not inspected by L&I and should be permitted and inspected by the local building department.

Q. Does L&I inspect “tiny homes?”

A. A tiny home used as a dwelling must meet state building code requirements. If a tiny home is fabricated in a factory or at some other off-site location, L&I inspects it as a modular structure. If a tiny home is built on site, the local building department inspects it. A tiny home that is used for temporary recreational purposes and is less than 400 square feet may be a Park Model RV. It must meet the requirements of ANSI A119.5 and have an L&I approval label. Park Model RVs are not approved for or intended to be used as dwellings.

Q. Can a tiny home be a manufactured home?

A. No. Manufactured homes can only be built by approved factories and must bear a HUD label.

Q. What is the Factory-Assembled Structures (FAS) program?

A. FAS is part of the Washington State Department of Labor & Industries. FAS regulates the prefabricted building industry. The program covers manufactured and mobile homes, modular buildings, temporary worker housing, recreational vehicles, recreational park trailers, food trucks and concession trailers mobile medical units, and commercial coaches such as portables.

View the glossary of common terms, acronyms and definitions used by FAS.

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