A composite wall assembly edge joint including a first composite buildup pad having a first tapered section is secured to and extends along a first composite face sheet. A second composite buildup pad having a second tapered section is secured to and extends along a second composite face sheet, wherein the first and second composite buildup pads are positioned between spaced apart first and second composite face sheets. A composite flute core member includes a tapered first portion positioned between and secured to the first tapered section and to the second tapered section. A second portion of the composite flute core member extends in a direction away from the tapered first portion of the composite flute core member and is positioned between, extends along and is secured to the first and second composite face sheets.