Aim of this thessis is of behaviour analyse of thin webbed box beams loaded by four point bending. Load force was increased, decreased and stayed constant durring the testing process. Flanges were made from beech and KVH – spruce lumber. Material of web was oriented strand board and fibre – gypsum board. Stiffnesses of nailed-, screwed- , stapled and pinned – laminated beams ware compared. In this thesis are measured behaviour of non – laminated TWB-s, which are shear bounded by nails, without lamination. The main stiff behaviour have beams beech flanged TWB-s which ware glued by nailing. Only in few cases was stiffness of beech flanged beams lower like spruce- flanged beams. Nailing in beech lumber is technologicaly difficult proces. Using beech lumber in thin webbed beams is looking possible. For safety using TWB – s it is necessary select lumbers without imperfections.