Repointing patio slabs

Patio slab pointing fails for a number of reasons – some simply to do with age, others relating to the method used for laying and pointing the slabs in the first place. Dry pointing (where a dry mortar mix has been used) has got a tendency to fair worse than a wet mortar mix, but if the slabs haven’t been laid properly in the first place, pointing doesn’t stand much of a chance anyway. Basically, if your slabs wobble, they need to be relaid before repointing. If the slabs themselves are secure, then the techniques shown and discussed below can be used.

removing mortar 1. Use a trowel to rake out all the old loose mortar from between the joints. Take care not to chip the edges of the slabs.
 brushing out old pointing 2. Brush off the slabs thoroughly with a hand brush to make sure you have as clean a surface as possible before you begin to infill the joints.
 mixing mortar 3. Pour some mortar mix into a bucket and mix it up with some water as directed by the manufacturer.
 repointing patio slabs 4. With a pointing trowel, press the mortar firmly down into the joints and be sure to ‘strike’ the joints, as shown, to ensure compact work.
 wiping away excess mortar 5. Keep as much mortar as possible off the slabs as it will stain them. Use a clean damp sponge to continually remove any excess.

Repointing tips

  • A bagged mortar mix has been shown here for convenience although you could mix up your own – a 4:1 sand to cement mix is fine.
  • There are other DIY products such as Slablayer that may also be used as a pointing material. There is more about this in my ‘Laying a patio’ guide, but basically you fill the joints with the dry Slablayer and then sprinkle water across the joints dampening the Slablayer which will then set like standard mortar.

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