Buildings and walls are commonly constructed with exterior walls composed of specially treated engineered wood panels, cement panels, fiber cement panels, glass-matt-faced gypsum panels, and gypsum/cellulose sheathing panels. The spaces or edges between these exterior panels are sealed using the disclosed dual-tape-core joint treatment system and method of the present invention. After curing, a color matching acrylic-epoxy scratch coat or elastomeric primer followed by a textured finish coat is sprayed, brushed or rolled on the exterior panels.