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?
The prefered method is to fill the space. To prevent heaving you could leave out some grout in several places around the bottom for weep holes. You could even lay the block and push a 1/2" X 1" stick through the bottom of the head joints to open them up. No moisture, no heaving.
I would use a polyethylene vapor barrier under the stone.
Wouldn't you need a foundation for something like that? Unlike a wood deck, masonry has zero tolerance for movement. I would think it would have to be built on a foundation that extends below the frost line. Not to mention the weight, I'm sure it would settle a lot.
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There is really only one time tested method.
First you need a wall below your frost line with a footer at the bottom. Usually the footing is twice as wide as the wall will be thick. 8 inch wall, 16 inch wide footer, by 12 inches deep. Good enough for a porch.
Then you fill the void and use a compactor, some thing you can tamp it down with ,until you are level with the top of the wall. Use water to help in the compaction, it settles the soil.
Then put a 6 mill piece of plastic over that.
Third is to build a 4 inch cap with 4 inch wire mesh lying in the concrete. This will help with any structure of the cap. It will not be as likely to break.
Then finally install your stone on top, the sides whatever you need. It will last longer than you think in GA.
The last thing is to sit around and enjoy your hard work...show it off if necessary.
These are the basics we use as professionals. Wood has no place with stone, the only other thing you could do is some drainage around the stoop(porch), but that depends on grades of the yard.
Have fun and good luck.