The key element to any successful pointing project is in the materials used. 
Hard cementitious mortars can be as harmful to a building as having completely open joints. The natural porosity of stone means that an element of water soaking will always occur. This only becomes a problem however when this water cannot escape.
An unsuitable cement mortar joint creates a hard barrier around the stone trapping moisture within the fabric.
This will eventually start to erode the stone as it forces it’s way back into the atmosphere. In extreme cases the freezing temperatures outside cause the water to expand and blow the face off the masonry resulting in unsightly damage and often structural issues.
