To obtain excellent resistance against an earthquake by attaching a short joist which crosses a long joist orthogonally to the long joist in a cross shape further and integrating them tightly by through reinforced bolts which reach both ends of the joists to form a cross-shaped cross assembly.

A short joist 2 is fixed on a long joist 1 temporarily, and a long bolt 3 passes through the long joist 1 from a beam of an end or a groundsill along the short joist until it reaches the beam or an end of the groundsill. A through hole is drilled in the long joist 1 by an electric drill in advance, bolts 3 are not fixed and are arranged in order, and three bolts are tightened. Nuts which are one set are put in and pass through it sequentially. Next, the long joist 1 is fixed solidly at both ends of the beam, and the straight going short joist 2 of a cross is fixed obliquely by driving nails to connect the whole assembly tightly by using the bolts 3. Consequently, it is possible to obtain rigidity owing to the combination of iron and wooden material and stop shaking of the joists completely.