WAC 296-150M-0360
WAC 296-150M-0360. When is design plan approval required for an alteration?
(1) Design plan approval is required when you make a structural alteration to your manufactured home. A design plan approval may require engineering by a professional engineer currently licensed and certified in the state of Washington.
(2) A structural alteration is a change to the body or frame of a manufactured home. For example:
(a) An alteration is made if you change the size of a room or the pitch of a roof on your manufactured home.
(b) Any addition such as a carport that adds structural load to the manufactured home and is not fully self-supporting is an alteration.
(c) Alterations or installations of other types of work (plumbing, electrical, etc.) that are incidental to the structural alteration.
(d) Rebuilding portions of the home or reroofing over existing roof.