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| Re-pointing irons for lime repointing jobs |
In the UK we are used now to see repointing being done using a pointing trowel or a brick jointer. However doing a proper job with lime mortar requires a different set of tools.
This is because joints should be cleared by a depth of more than their width, as a very thin layer of mortar might not adhere (BRE guidance is for all but the narrowest of joints
is that the depth should be twice as great as the width of the joint).
The skill requirement
for raking out should not be underestimated; it is all too easy to remove
the edges of stone and bricks, especially if the joint has been filled with cement mortar. Traditional lime mortars are relatively
soft and should be raked out by hand with a sharp instrument. A simple
spiked instrument should suffice, although where the mortar is sound it
may be necessary to use a sharp chisel or flat bladed quirk. However,
if the lime mortar is sound, the question that must be asked is whether
it is necessary to remove it or not.
After
the masonry has been correctly prepared for re-pointing the matured
mortar should be thoroughly knocked-up to the consistency of glazing putty, The the mortar should be pressed firmly into the pre-dampened joint void until it is filled out to
the face and feels solid. Mortar spreading out into a thin layer across
the facework must be avoided, as this can lead to future water penetration. The jointing tool required to deliver and press
in the mortar must be one that fits the relevant joint sizes. Small trowels
may be adequate for large joints in rubble stone walls and some types
of brickwork, but for fine masonry purpose made jointers or pointing irons
should be used.
When the mortar is applied it is extremely workable, but be aware that it rapidly
becomes much firmer as moisture is drawn out of it by the masonry. It
must then be gone over to compact and consolidate it and bring it to the
required profile and finish. Different finishes can then be created using a brush or jointing tools depending on what effect you are trying to achieve / match.
