California Code, Vehicle Code - VEH § 362

A “house car” is a motor vehicle originally designed, or permanently altered, and equipped for human habitation, or to which a camper has been permanently attached. A motor vehicle to which a camper has been temporarily attached is not a house car except that, for the purposes of Division 11 (commencing with Section 21000) and Division 12 (commencing with Section 24000), a motor vehicle equipped with a camper having an axle that is designed to support a portion of the weight of the camper unit shall be considered a three-axle house car regardless of the method of attachment or manner of registration. A house car shall not be deemed to be a motortruck.