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How to Repair a Slate Patio

James J. Siegel

Slate has been a popular choice for outdoor patios because it is both attractive and durable. But even the most durable stones may need to be repaired. Sometimes extreme weather conditions can do damage to slate. Also, dropping heavy objects on your slate patio can cause cracks and fissures. The good news is replacing a piece of slate is quite simple. If your slate patio was installed on a sand bed, just dig out the slate piece and replace it. If the patio uses mortar, you'll need to chisel away the mortar and take out the broken piece.

While slate is a durable building material for patios, it sometimes needs to be replaced if cracks occur.
  1. Break apart the mortar surrounding the piece of slate by using a chisel and hammer. Direct the chisel toward the broken stone in order to avoid damaging neighboring stones. Keep chiseling all the way around the stone until all of the mortar has been broken apart.

  2. Break the damaged piece of slate into smaller pieces by using a hammer. This will make it easier to remove. Do not pound the piece of slate too hard. This can also break nearby stones.

  3. Take the broken pieces of slate out of the hole. If there is any more mortar still surrounding the sides or the bottom of where the slate was located, chisel it away.

  4. Take the replacement piece of slate and fit it in the hole. If the slate is too big for the space, use a hammer and chisel to cut the stone to the appropriate size.

  5. Remove any dirt and debris that is still in the hole by using a shop vacuum.

  6. Dampen the inside of the hole by using a spray bottle. Mix a batch of mortar and spread it in the bottom of the hole. Take the replacement slate and push it firmly into the mortar. Then use a straightedge to make sure that the new piece of slate is level with the nearby pieces of slate. If the slate is not level, add or subtract some of the mortar in the hole. If you are satisfied with the slate placement, allow the mortar to dry overnight.

  7. Mix another batch of mortar and place it in a grout bag. Use the spray bottle again to dampen the area around the new piece of slate. Now squeeze the mortar out of the grout bag and into the joints surrounding the new piece of slate. Smooth out the mortar with a small trowel. Allow the mortar to dry for another 24 hours.