Fundamental relations of continuum mechanics are the starting-point for the derivation of a surface-related finite shell element. The variational principle of Hu-Washizu is stated and modified. In this formulation the stress tensor is eliminated from the functional with the aid of an orthogonality condition. This allows to introduce additional strain parameters to avoid or reduce locking phenomena respectively, whereby an expansion of the element stiffness matrix can be prevented. The continuum mechanical relationships are prepared for the utilization in the shell theory with a kinematical restriction. The chosen linear ansatz for the displacement field over the thickness is the only restriction of the body's motion. The contact conditions are introduced by following the continuum based formulation as suggested by Laursen and Simo [1]. This formulation is extended to handle adhesion and is used to model the interface behavior in layered structures.