Abstract: A drainage system for draining rain water and internal moisture from the rear of exterior wall panels so as to effectively drain such rain water and moisture outwardly to the outside of the wall panels. The system inlcudes a vertical sealant joint behind adjoining exterior wall panels to sealingly space the wall panels from their support. The space includes foam back-up tapes, vertical sealant, drain tubes, and gutters so arranged as to effectively drain, outside the walls, through weep holes, rain water as well as moisture that tends to accumulate behind the walls. The present system drains both the vertical and horizontal joints of exterior wall panels.