The building of low and mid-rise modular-based timber buildings is a growing industry sector worldwide. Today, the use of prefabricated light-frame volume modules (sometimes with CLT walls) is a prevalent and innovative construction method. This building method has many advantages, though some of the technical solutions and design methods are quite challenging and should be optimised without risking structural safety. The paper presents results from an ongoing research project that deals with testing and numerical analysis of light-frame timber test modules. It focuses on the testing and simulation of global racking stiffness of different types of test modules and the testing of a friction-based joint between two test modules. The modules showed larger shear load carrying capacity than expected. They also showed a ductile failure behaviour and large variation in racking stiffness between different types of test modules.