Abstract: A mattress foundation having a rigid frame covered at least in part by a continuous stationary horizontal top surface. A layer of resilient material overlies the stationary top surface. An open grid freely rests on this layer and is resiliently supported by it. A powered vibrator unit is fixed to the grid and is physically clear of contact with the frame. The grid is resiliently covered. It is capable of imparting vibratory movement about the top surface of the completed foundation assembly. In one form, a section of the grid is resiliently supported on the frame by interposed upright springs.