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Washington · WA
Steel & concrete modular homes in Washington
Modular homes are built to state and local building codes and set on a permanent foundation. Here is what applies in Washington.
Washington program
- Administering agency
- WA Dept. of Labor & Industries (L&I), Factory Assembled Structures program
- Program / authority
- RCW 43.22; WAC 296-150F (Factory-Built Housing and Commercial Structures)
- Code basis
- Not verified. Confirm with the local building department.
- Inspection & seal
- Building must have an L&I insignia before shipping from the factory; plans must be approved, and licensed professionals can now review plans.
- Good to know
- Wildland-Urban Interface code compliance required for modular structures since March 15, 2024; local departments decide where they may be sited.
- Official source
- https://lni.wa.gov/licensing-permits/manufactured-modular-mobile-structures/laws-rules
Summarised from public sources; rules change. Confirm with Washington’s agency and your local building department before ordering.
Your project in Washington
Step 1
Confirm zoning & permits
Local jurisdiction sets lot, setback and design rules. See Permits & Zoning.
Step 2
Plans reviewed to state code
We stamp plans for the code that applies in Washington.
Step 3
Factory build & inspection
Third-party or state inspection happens in the factory, then final on site.
Step 4
Set, connect, certify
Modules crane in, joints are torqued and inspected, and local sign-off issues the CO.