In order to benefit from the advantages of fully threaded self-tapping screws as reinforcing elements, it is essential to have detailed knowledge about the strength and stiffness of screws with different shank to grain angles subjected to combined axial and lateral loading. In this paper a design model is proposed for the calculation of the load-carrying capacity and stiffness of screws with different shank to grain angles subjected to loads perpendicular to the grain by accounting for the effective embedment of the screw in the timber. The proposed model is based on commonly used material properties and other established design models and fits well the influence of the angle between shank and grain direction on the joint's capacity and stiffness. However, detailed knowledge about the specific input parameters in the design approaches is necessary in order to achieve a reliable prediction of the load-carrying capacity and stiffness of the individual screw.