Abstract: The invention relates to improved means used to fold and/or unfold a portable building of the type in which members are hingedly connected to a rigid central section to reduce its external volume and facilitate transportation of the building. The rigid central section comprises a floor, walls and roof. Additional roof members are pivotally connected to the roof along opposed parallel edges so as to be movable between an extended position in which they form a continuation of the central roof, and a further position in which they are disposed parallel with the vertical walls of the central section. Additional floor members are connected to opposed parallel edges of the central section floor which are parallel with the additional roof members. The additional floor members are moveable to form an extension of the central section floor or to be parallel with the central section walls.