Abstract: A prefabricated building structure having a collapsible roof and adapted to be transported by a road carrier vehicle is described. The prefabricated building structure is provided with at least opposed parallel load bearing side walls. A roof section having a plurality of spaced roof rafters is pivotally connected by one or more pivot connections to a respective one of a top plate of each of the load bearing side walls. The roof sections are interconnectable to one another when the roof sections are disposed angularly upwards to form a raised pitch roof structure. A leverage beam is connectable to one of the rafters of each roof section and is securable to a cable which is secured to a pulley whereby to permit the roof sections to be raised or lowered.