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Many older homes in Sydney were built and supported upon clay-type soil, rather than bearing on solid rock. However, over time, the clay will shrink and subside, therefore cause the footings and foundations to be unstable and sink at varying levels, which typically causes settlement and cracking of the building structure, particularly of the brickwork. Further compounding the problem is that older homes usually had relatively fragile brick type footings, rather than of concrete.

To rectify this concerning problem, the foundations of the house need to be supported and pinned positively to solid rock, further below. The process of carrying out this work on an existing building is known as “underpinning”.

The main visible sign that your home may need underpinning is when large cracks appear in the brick walls, which then increasingly open up.

Other factors related to dropping of foundations include poor subfloor ventilation and water drainage, or poor construction materials.


  • Settlement and sinking of the soil (typically clay) beneath the foundations of the house, causing displacement of the supports, leading to unlevel flooring and cracked walls
  • Inadequate structural support at the foundations
  • Poor subfloor ventilation and water drainage (also see ‘Subfloor Ventilation and Drainage’)


  • Inspect and investigate the structural support and foundations issues, including with our Structural Engineers, if required, as well as provide recommendations
  • Propping and bracing the existing ground-level structure
  • Raising and relevelling of the structure, via the foundation areas
  • Construction of solid underpinning for the foundations, using concrete and includes carrying out step-by-step hand-excavation beneath the existing foundations to solid rock, in order to properly support the building
  • Repair or replacement of cracked brickwork (also see ‘Brickwork Repairs’)