A structural element for use in forming a structure, that includes first and second longitudinal members that extend between opposite ends of the element. The longitudinal members have inward and outward faces, and a pair of side faces extending between the inward and outward faces. The element includes first and second lateral members that extend between the first and second longitudinal members. The first and second lateral members each have an outer surface. The outer surface of the first lateral member is substantially flush with a side face of each longitudinal member to form a substantially planar surface extending across substantially an entirety of a first side surface of the element. The outer surface of the second lateral member is substantially flush with a side face of each longitudinal member to form a substantially planar surface extending across substantially an entirety of a first side surface of the element.