Typical defects that may trigger cracks include any one or a combination of:

• Ground movement – Subsidence, land slip or heave
• Inadequate support – Localised foundation failure, lintel failure, masonry arch failure, etc.
• Insufficient restraint – Lack of wall ties, restraint straps, poor bonding, etc.
• Resizing – Expansion or shrinkage due to thermal or moisture variations
• Rusting metals – Wall tie corrosion, expansion of hoop irons or fixings, etc.

Before a crack repair can be done the cause of the fracture needs to be established and eliminated.

Generally crack repair strategies fall into one of two categories:

• Sub-structure repairs for below ground foundation movement issues, typically an insured risk
• Supers­truc­ture rein­for­cement for above ground building defects, typically an uninsured risk

Sub-structure repairs may include underpinning or piling.

Supers­truc­ture rein­for­cement generally includes structural repairs accomplished by the insertion of helical bars that form retrofitted brick beams or are used for crack stitching. Replacement wall ties and restraints tie cavity or separating façade walls whilst resin injection systems efficiently fill and seal cracks in walls

Once the cause of the fracturing has been eliminated then all that is required is to reinforce the cracked masonry so that it once again acts as a composite structural unit. Crack repair techniques include mechanical brick stitching and crack injection resins, whilst various tie and restraint systems help to transmit and share loads.