Abstract: The invention of rapidly erectable housing units providing a number of properly shaped and interfitting wall sections. Beside the wall sections the units include interlocking or laid-uproofing applied to truss rafters. interlock to the erected walls. The wall sections are provided with structural base plates and headers for interlocking the walls into sturdy non-rackable condition to maintain the stability of the unit. The interfit of the wall sections may be in several forms such as matching, slotted grooves to afford sliding connection between sections and may also include mortise and tenon arrangements on the ends of sections with the tenon passing through the mortised area for the attachment of a locking element on the extending end of the tenon as well as the mortise position. The mortise and tenon arrangements, particularly at corner areas of the unit may include a plurality of interfitting elements rather than a single arrangement which will allow for more secure joining of the sections.