Abstract: A composite wood panel is disclosed, the wood panel having parallel first and second longitudinal edges, and parallel upper and lower faces, and comprising: a groove formed along the second longitudinal edge, a complementary shaped tongue formed along the first longitudinal edge, and a barrier layer. A first surface extends from the tongue to the upper surface and forms a generally obtuse angle, &agr;, with the upper surface, while a matching surface extends from the groove forming a generally acute angle, &bgr;, with the upper surface, and the sum of &agr; and &bgr; is from about 175° to less than about 180°. The composite wood panel allows for convenient and fast assembly, particularly in constructing roofs, and also provides resistance against the penetration of water through the structure formed by the panels.