Can flagstone be put on top of a concrete patio?

Question

We have an exsisting concrete patio with a few hairline cracks and "pits" starting to appear. Would it be ok to put flagstone down?

Answer 1

You could do that, and the answer above points out the relevance of structural integrity. That means that cracks in the slab can telegraph and become cracks in the stone when it is bonded to the slab. There is one other consideration, which is water problems that can develop from freezing in voids around the stone. Not a problem in all locations, of course. However, it is very labor intensive.

An alternative that you might consider is what is called pavers, and they can work very well as a cap of a slab patio. These are solid brick or cast concrete products, and can be a very handsome installation. To install them over a patio, you set only the perimeter row in mortar. This makes a containment for the center field. The center slab has 3/4" holes is drilled in several locations for water drainage, then is given a layer of masons sand the same thickness as the perimeter mortar bed. The pavers are placed inside, butted together, and the sand allows some vertical adjustment to keep the surface flat. There is some cutting required around the edges, but overall it is less and easier than flagstone. After all pavers are in place, more masons sand is thrown around on top. This is swept around the surface with a broom until all the cracks are filled with sand. The sand takes up the slack and locks everything in place. Sweep off what's left on the surface, and it's done. This process does not telegraph cracks and is not damaged by freezing. It's also easy to change and even reuse if conditions call for it.

Custom Builder-

Answer 2

you would not normally put flagstone on top of concrete there is an extreme likelihood that they would eventually break from any slight unevenness.you could put a few inches of sand over the concrete and then lay the flagstone or do what i did get a sledge hammer and think angry thoughts the concrete wont stand a chance. PS wear eye protection.

Answer 3

Sure, as long as the concrete has structural integrity and the new flagstone is not higher than your home's slab or floor height (if patio is attached to home).