This is a study of partial composite action in timber constructions. The aim was to determine a method for calculating the flexural rigidity also known as bending stiffness in CLT-constructions made of CLT and wooden latches with screw connectors. The chosen method became a combination of Eurocode 5 and mathematical models. The goal was to try to show how partial composite action between CLT and wooden latches can improve the flexural rigidity of the construction to allow a longer span in floors and higher loads in walls.   The results show a significant increase in flexural rigidity to the extent that the total rigidity in some cases is almost as high as with full composite action. The addition in rigidity is highly dependent on the angle of the screws as well as the span of the construction. This makes easy assembly of the screw connection an important question as screws mounted at an angle gives a significantly higher capacity but is more difficult to assemble compared to screws at right angle. The calculations show that constructions with no composite action, where the latches’ rigidity is added to the CLT´s can be a first step towards higher utilization of the material, especially in walls. The advantage with no composite action is that the demands on the connection are lower which makes for easy assembly. In conclusion partial composite action can be an interesting topic for further studies but with more focus on the connection design with respect to the assembly on site. Also, areas as cost and building acoustics are relevant for further studies.