When it comes to determining the height of a crown molding ledge, there are a few rules. If your ceilings are a standard 8-feet high, the height of your crown ledge should be two and a half to six inches. If your ceilings are nine feet high, your crown ledge should sit at three to seven and a half inches tall, and for ten-foot-high ceilings, keep your crown ledge at three and a half to eight inches high.