How To Repoint Natural Stone Patio Slabs

No matter how well-built your natural stone patio is, over time it may become affected by the movement of the ground beneath it, resulting in damage to the cement joints between the slabs.  This can make the slabs uneven and wobbly, presenting a dangerous trip-hazard to users and spoiling the look of the patio.  To correct the damage, you'll need to 'repoint' the slabs.  If you have good basic DIY skills, you can do the job yourself.  Alternatively, a good local patio firm or builder will be able to carry out the work for you.

Read on to find out how to do it.

What you'll need

  • eye protection
  • gloves
  • brick trowel
  • lump hammer
  • bolster
  • shovel
  • plugging chisel
  • stiff yard brush
  • play-pit sand
  • soft brush
  • cement

All these items can be obtained from good DIY stores if you don't already have them in your tool set.

How to do it

  1. The first thing to do is to get rid of all the old, damaged mortar.  Always wear gloves and eye protection for this job, as flying mortar chips can be dangerous.  Use a hammer and bolster chisel for this task, or a plugging chisel for any particularly tight joints.  Angle the chisel pointing away from your body into the damaged mortar, and tap it firmly on the handle with the lump hammer to dislodge the cement.  
  2. When you've finished removing the old mortar, sweep the surface clean with a stiff yard brush.  
  3. Make up a dry mix of sand and cement at a ratio of 1:1.   
  4. Beginning in one corner of the patio, sprinkle the mixture along the first few joints.  Using the soft brush, sweep all the new mortar mix into the joints until they are completely full.  This is extremely important as any air pockets left in the mortar will cause it to set unevenly and ultimately lead to cracking.  
  5. Continue right around the whole patio until all the joints are completely full.  Brush any excess mortar off the patio and leave the pointing to settle.

Over the next week or so, the mortar will harden naturally as it absorbs moisture from the air and from the ground beneath the stones.  This is the best way to allow the new pointing to 'go off' as it keeps the mortar flexible, which means it is much less likely to crack.

In conclusion

You can repair any damaged pointing on your patios simply and effectively by following the guidelines above.  Alternatively, contact your local patio builder or contractor for more advice and assistance.