This document discloses a method for joining beam portions (10a, 10b) together, short side to short side, so as to form a beam (1). The method involves providing first and second hollow beam portions (10a, 10b) which have substantially identical cross sections comprising a first pair of opposite inner surface portions (11a, 11b) and a second pair of opposite inner surface portions (12a, 12b) which are located substantially at right angles to the first pair of surface portions, providing first and second jointing elements (13a, 13b), inserting the jointing elements into the cavities of both beam portions such that each of the jointing elements bears against one of the first inner surface portions (11a, 11b), respectively, and against both of the second inner surface portions (12a, 12b), providing at least one wedge (14a, 14b) which is inserted between the jointing elements (13a, 13b) such that these are pressed in a direction away from each other and toward a respective first inner surface portion (11 a, 11b), and providing at least one pressure- generating connector (21 a1-21 a4； 21b1-21 b4), which presses the second inner surface portions (12a, 12b) in a direction toward each other, such that the jointing elements are clamped between the second inner surface portions (12a, 12b).
