The study of the actual state and the strengthening intervention developed on a large industrial timber building erected in 1921 in Cardona (close to Barcelona) is presented. The external dimensions of the building are 85.0 m long, 37.7 m wide and 32.42 m high. Some main frames had presented historical failures, without falling down, in the tie member of the roof just under its top. Structural analysis showed very high stresses at that point that explained such failures. A minimal and low cost intervention was designed to resist excess bending stresses by enlarging timber section where it was possible. Close to connections, where enlarging cross section of the members was no possible, it was decided to use stainless steel ties.