my sub-floor consists of 3/8 inch wafer board.and the house is on a busy street(the FREEWAY,TURNPIKE) every day the house shutters due to semi's,dump trucks,belly dumpers etc. comparable to a 3.5 earthquake.I am figuring on bracing up the floor joists to reduce movement there,adding 1/4 plywood on the subfloor and cement board before tiling.will this hopefully be enough to again reduce the movement?all rooms adjacent to bathrooms will have 3/4 inch hardwood . I am trying to avoid a real big difference in the levels of flooring