Hairline cracks that appear in brickwork can be unsightly and cause concern however it is not usually a major issue unless the cracks are wide and are replicated through to the inner leaf. In cases like this it could indicate a structural issue and will require investigation by a qualified structural engineer.
The majority of hairline cracks in concrete or clay brickwork are caused by moisture or thermal movement. They are usually classed as micro (hairline) cracks which either run through the bricks themselves and/or the bricks and the mortar.
They can occur when the mortar is too strong. If mortar is too strong it prevents sufficient flexibility within the structure.
Cracks can be dealt with as follows:
- Very fine micro cracks: it may be more practical to leave them as any repairs may actually make them more noticeable.
- Slightly wider cracks: Cracked mortar can be raked out and repointed. The cracks in the bricks can be repaired by filling and tinting if necessary.
- If absolutely necessary it is possible to cut out the bricks and mortar and replace. This should be carried out by an experienced bricklayer who has been trained to do this type of replacement. It must be acknowledged that this type of repair may look unsightly at first as it can be difficult to achieve an exact colour match for the mortar. Any differences in colour usually dissipate as the mortar matures.