I want to replace my wood front porch with stone. I plan to build a concrete block frame and then face it with stacked stone, which is readily available here. I have two questions: First, do I have to fill in the space with dirt or sand to support the stone floor? Or can I use treated wood to span the space and then lay stone on top of it? My concerns about filling the space with sand or dirt is that it may "heave" during very cold weather. (Heaving, I understand, is when moisture gets into it and when it turns to ice, it expands and pushes the floor up.) My concern about using stone over wood joists is that it may be too flexible and cause the grouting to break. Does anyone know how to deal with the space between the block frames?