Abstract: An improved expandable mobile home having hinged longitudinal joints between a central roof supported by a plurality of spaced sloping rafters and horizontally extending purlins secured on, and extending transverse to, the rafters, and maintained elevated by a plurality of aligned, spaced vertical posts, and a pair of folding roofs having a plurality of parallel extension rafters each corresponding to one of the spaced sloping rafters supporting the central roof, between a central floor and a pair of folding floors, and between the pair of folding floors and a pair of folding walls, and having hinged vertical joints between central end walls and pairs of folding end walls, the improvement residing in specific structures by which the mobile home is maintained in weather-tight state whether collapsed for transport or expanded for residence use.