This is the process where new mortar is inserted into prepared joints between brick or masonry. By carrying out this work the brick/masonry will continue to retain its stability. Good quality pointing also has great aesthetic value.
Use of cement mortars is extensively regarded as being detrimental to solid wall constructions as they can drastically change the way a wall handles water. Their 'closed' pore structure traps water in the wall instead of allowing the wall to 'breathe'.
It is essential that solid walls without a cavity are kept in good repair for the interior to remain dry and practical.
The selection of the most appropriate mortar is essential before work commences. Analysis of the original mortar may be required to formulate the correct match.
- The selected mortar needs to be slightly weaker than the stone or brick substrate. The pointing acts as a conduit where moisture that enters the building is allowed to pass back to the surface. If a very hard and dense mortar is selected then the moisture tends to pass out through the interface between the stone and pointing. This in turn causes damage to the face of the stone or brick.
- Matching the colour/texture of the original mortar can be achieved by adjusting the various ratios of aggregate used.
- Point a trial area before the job commences for approval by the client/architect.
- Before pointing commences, dampen down the masonry joints using a pump sprayer.
- Having selected the most appropriate mortar, this needs to be mixed to a relatively stiff consistency, using the absolute minimum of water to avoid later shrinkage.
- The new mortar should be placed into the joint using a pointing iron. A standard trowel should not be used, as they cannot fill the back of the joint.
- The mortar needs to be pushed firmly into the dampened joints.
- The joints should be finished in accordance with the original form where evidence exists.
- On large joints, pinnings need to be inserted into the mortared joint. This reduces the volume of mortar used, aids carbonation and helps reduce shrinkage during setting.
- A flush finish, fractionally recessed is a very acceptable finish giving both the masonry and the pointing the best possible weathering surface.
- Mortar should not be smeared over the face of the stone/brick if the masonry/brick is to be exposed.
- The finished mortar should be compacted into the joint when a partial set is evident using a stiff bristle/churn brush. The brush should be struck at the joints and not dragged across the joint. This gives an even and textured finish, which aids evaporation of moisture from the joints. Various other techniques can be employed to give the appearance of age and weathering.
- Keep damping down the newly pointed work for at least ten days to aid carbonation and avoid shrinkage.
- Protect the finished work from frost, sun, wind and rain by using a combination of hessian sacking and plastic until fully cured.
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