If a wall being either stone or brick is built with lime, it is extremely important that it is repointed with lime mortar.

If this is not done it will cause further damage to masonary and create damp.

Examples of this are very common when a wall is repointed by a non professional.

The mortar joints need to be softer than the brick, as the water will penetrate and escape through the softest route.

You want this to be the brickwork / stonework joint, not the brick face.

Examples of this are brick faces being blown.

Pointing with cement over lime will trap water behind the joint, washing out the lime creating a void behind the cement joint.

In winter trapped water or moisture will freeze, expand and damage the masonary.

If a house is built with cement it can be pointed with cement.