How to Repair a Flagstone Set on Concrete

Flagstones set on concrete create extremely strong paved surfaces with a large variety of flagstones giving your pavement the look you desire, while the concrete base provides the stones with a stable long-lasting subsurface. Even with the strength of the combined materials, the flagstones can still crack or break, leading not only to a loss in visual appeal, but also to the creation of a tripping hazard as well. Repairing a flagstone isn't a difficult task though. All that's required is a bit of concrete patching material to replace the broken sections, replacing the flagstone with an equally strong patch that will last the remaining life of the stone itself.

Broom
Chisel
Hammer
Wire brush
Garden hose
Concrete bonding adhesive
Brush
Portland cement
Masonry sand
Bucket
Wooden stirrer
Putty knife
Plastic sheet
Bricks

Instructions

- 1
  Sweep the surface of the flagstone and remove debris from any cracks in the stone with a broom. Pull away any broken pieces of flagstone and concrete as well. Use a chisel with hammer to remove any loose pieces still attached, cutting off the pieces at the base with the tip of the chisel.
- 2
  Widen any cracks toward the bottom with the hammer and chisel so that the base of the crack is wider than the top. The small ledge created will enable the patching material to hold inside the crack with greater security. Clear away any remaining debris with a wire brush.
- 3
  Wash off the surface of the flagstone with a garden hose to increase the moisture on the stone. Additional moisture will prevent the flagstone from leeching any moisture from the patch as it cures.
- 4
  Cover the damaged areas of the flagstone with a concrete bonding adhesive using a brush. Allow the adhesive to dry to the point where it's no longer shiny with wetness but remains sticky when touched.
- 5
  Mix a patching material for the flagstone using one part Portland cement to 2 1/2 parts masonry sand in a bucket. Add water to the mix and stir with a wooden stir stick until you have a peanut butter-like consistency to the concrete.
- 6
  Fill the cracks throughout the flagstone with the concrete patch using a putty knife to press it into place. Scrape over the patch with the edge of the blade to even it out with the rest of the flagstone surface.
- 7
  Cover the flagstone with a piece of plastic sheeting. Weigh the edges down with bricks to keep the sheet from blowing away. Allow the patch to cure for 48 hours then remove the sheeting. Wait an additional five days before walking over the flagstone.

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