The invention relates to a load-bearing structure for a building, comprising a first set of beams arranged substantially horizontally and a second set of beams arranged at right angles in relation to the first set of beams, said first and second sets of beams forming a frame, which confines a number of rectangular sections. Each frame section can be occupied by a panel, such as an infill, a window, a door or a solar energy collector. The beams of at least one set is provided with one or more feathers, which in the mounted state, projects at substantially right angles to the frame plane, runs along substantially the entire length of the beam in parallel with the length axis thereof along the side of the beam so that no part of the feather projects above the upper level of the frame, and defines a groove running in parallel with the length axis of beam, the groove being located between the main portion of the beam and the feather. Feathers and grooves may be provided on both sides of the beams. Windows or other types of panels are mounted on the load-bearing structure by fitting grooves in the window frame or mounting brackets secure thereto over the beam feathers.