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 lime mortar
The Victorians invented Portland Cement to set under water for building harbours and sewers. It has also proved useful for making concrete.
However it has no business getting involved with stone buildings.
Lime mortar has been proved the ideal building material for stone of all types with a three thousand year track record of successful performance.
It is porous and freely conducts moisture through the structure. It sets hard where it is in contact with the the air, but remains plastic within the structure, which allows it to compensate for any movements.
Cement on the other hand, as a very hard crystaline material, is full of microscopic cracks each of which will draw moisture into a stone structure by capilliary action and trap it. The building can only dry out through the surface of the stones, and this mechanism accelerates the erosion of these stones.
Cement mortar damages stone buildings.
Lime mortar, properly applied, not only looks great. it works with the structure, not against it.
Both sides of this semidetatched house were badly pointed in the same nasty cement mortar. It is possible to remove this without damaging even this type of soft sandstone, by very carefully breaking it up a little at a time. The improvement in the appearance of the property is dramatic and well worth the effort. It is also much better for the building in the long run.
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