Abstract Glulam is manufactured by gluing graded timber boards on top of each other with standard, stiff adhesives to form a beam. The research presented here is concerned with the use of a single flexible adhesive layer at a certain position of the beam cross section instead of the standard, stiff adhesive. In a first step, fundamental theoretical considerations for a favourable redistribution of the stresses over the cross section of the beam are presented and the position of the flexible adhesive layer is optimized in order to obtain the highest bending resistance of the total beam. Further calculations help to determine the requisite mechanical properties of the adhesive layer. They are communicated to the adhesive manufacturer as target values for the development of new adhesives.