Never ignore substantial cracks across large areas of brickwork, particularly if the brick, rather than the surrounding pointing, is cracked. This can indicate serious structural problems, such as subsidence, so consult a builder or local authority building control officer. If a crack is stable, you can repair it yourself. Remove cracked mortar and then repoint the area in the usual way. If one or more brick is cracked through the middle, use a club hammer and cold chisel to remove and replace the brick. Follow the same steps for...