Abstract The demand for temporary buildings has increased during the last few years. The main reason for this increase is the need for temporary housing.  This thesis contains the development of a construction solution that locks, joins and seals sandwich panels together in temporary buildings. This solution also explains how to mount, de-mount and re-mount the buildings and was developed in cooperation with the commissioning company Swetech Design AB.   The project has been limited to just the horizontal joints of Swetech Design AB´s sandwich panels. The panels which the construction solution is going to be applied on have the dimensions of 2703 mm in height, 2297 mm in width and a thickness of 206 mm. The core consists of cellular plastic that is laminated with a material that consists of fiberglass and polyester.   The pre-study consisted of literature studies of various types of joints, the important properties needed in order to make an airproof construction and the various building requirements for temporary residents. The pre-study also consisted of a visit to the module building company Mobile Composite Solutions (MCS) which helped in acquiring knowledge of mounting big units and the manufacturing technique RTM. Even inventories in different branches were made, to get knowledge around the different possibilities and variations of locking, sealing and joining parts.   After the completion of the pre-study a requirements specification and two function analysis where made that put demands and requirements on the concept solution and expressed the concept in terms of functions instead of solutions. The requirements specification and the function analysis became the base of the idea generating phase. This phase resulted in partial solutions and complete solutions which were then combined together to establish different concepts. Through elimination methods, screening tools and discussions together with the commissioning company a final concept was chosen. The concept is built on a tension joint in combination with a sealing profile and a locking device made of an angle steel, bolt and nut which can join and seal the sandwich panels.   The concept has been visualized in the form of sketches, CAD-model, a physical model on a cut-out between two sandwich panels in scale 1:1, basic drawings and a component list. A proposal for continued work has also been presented in order to assure that the construction meets all the requirements listed in the requirements specification and to make it possible for the commissioning company to implement the concept.