A system for building a load bearing structure for supporting a compressive load, the system including a plurality of wooden members; wherein a protrusion of a second member is locatable within a recess of a first or third member to interconnect the first and second or third and second members together to form the loading bearing structure, wherein the protrusion is not rotatable within the recess, and; wherein the third member has a recess with a depth greater than the height of the protrusion of the second member such that a cavity is formed between an upper inner wall of the third member and a top portion of the protrusion of the second member when the second and third members are interconnected.