To sufficiently ventilate an underfloor and contrive the restoring force of a rubber material by supporting a load by steel balls arranged between metal fittings for a sill and a foundation, and transmitting a slight movement of the foundation by the rolling steel balls in an earthquake and bringing out a base isolation function together with the rubber material.

Steel balls are arranged between a metal fitting 11 for a sill and a metal fitting 12 for a foundation to support a load of a house by the steel balls arranged at the lower part of a column and transmit it to the foundation. In this case, a rubber material 6 is filled between the metal fitting 11 for the sill and the metal fitting 12 for the foundation and fixed therebetween to form a space for the steel balls and the rolling movement. The vibration of the foundation is attenuated by the rolling steel balls and the rubber material 6 and transmit it to the sill in an earth-quake to bring out the base isolation function. In this time, several devices are installed between the sill and the foundation to form a ventilation space. The sill and the foundation is restored to the original position and the shift between them caused by the vibration is reduced by the restoring force of the rubber 6 as the earthquake settles. In this way, the underfloor moisture is reduced to prevent the sill from corroding, and ventilation, base isolation, connection of the sill and the foundation can be realized in a simple structure, and the dislocation between the sill and the foundation caused by an earthquake can be removed.