The Preparation, this is just as important as the pointing it’s self.
Using a plugging chisel or picking hammer to ensure the stone or bricks are not forced apart, rake out existing pointing that is defective to a depth usually equal to twice the width of the joint, and not less than 20mm.
Damping down the joints.
Joints should be first dampened down to reduce the suction and prevent the lime drying down to fast this will also reduce cracking and shrinkage. Leave enough time for the stone or brick face to dry to prevent smearing. Mortar mix should be as dry as practicable to allow maximum compaction in the joint.
Gauging of the mix.
Normally a good mix is 3/1 mix of good quality, coarse sharp sand to mature lime putty for internal and external pointing.
Normally you start pointing at the top and work down to allow for cleaning up and spraying of the wall to continue. Use a pointing key or metal spatula and force mortar into joints from a hawk. If joints are deeper than 20mm, they will need to be dubbed out first to avoid shrinkage. Pointing can either be finished flush or rebated a little, depending on the width of the joints.
Once the mortar is ‘green hard’ i.e. firm enough to brush without smearing but still malleable) brush or tamp the joints with a churn brush. This will enhance the aggregate and give a coarser texture to the pointing.
The drying rate of the mortar is important, to control the rate of drying, external pointing should be mist sprayed. It should also be protected from the direct sun, wind, and frost in the winter time. We normally recommend a sheeted scaffold and hessian cloth to provide a more controlled environment.
Lime is a caustic substance so it is imperative that operatives wear eye protection protective gloves and clothing including dust masks when mixing and always follow the safety instructions listed on our labels.
Owners of listed buildings can, in some cases, get grants or loans to help them with repairs and maintenance.
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