New clay bricks undergo a slight expansion when new.  If restrained this can lead to cracks and bulges, often near quoins (corners).   If unrestrained the brickwork may slide on the DPC.  This movement will occur early in the life of the building and for up to some 20 years.  Any damage generally occurs early in the building’s life. 

 

Brickwork below the DPC may also bulge outwards due to the swelling of hard core.