Abstract: A roof panel construction system adapted structurally for use on a new roof, or over a pre-existing roof, dead level flat or steep, said system comprising a series of panels each having first and second metallic cover sheets, a structural and thermally protective barrier layer encased by said cower sheets and a nose and pocket construction on two adjacent edges formed so that the nose of a first panel will conformably fit into the pocket of a second panel and be mated thereto, said nose and pocket structures further comprising a plurality of sealing strips so that the joints between said panels are automatically sealed and spaced and become resistant to thermal and fluid leakage, said sealing strips being enclosed within the joint to assure maximum effective life of the system.