Traditional method
Mass concrete underpinning
The oldest and most direct form of the craft: excavate a short bay beneath the existing footing, pour structural concrete to a designed depth, let it cure, dry-pack the interface, then move to the next bay in an engineer-approved hit-and-miss sequence. Nothing about it is exotic, its strength is that every pin is visually verifiable before it takes load.
Scope
What this covers
Bay-by-bay excavation in the sequence set by the structural design
Formed mass concrete pins taken to the specified founding stratum
Dry-pack packing between pin and existing footing to establish load transfer
Engineer hold-point inspections of open excavations before each pour
Backfill, compaction and surface reinstatement on completion
Timing
When it's needed
Suited to sites where competent ground lies at modest depth, access allows hand or small-plant excavation, and the structure can tolerate staged work. Common on brick homes with shallow strip footings over clay that reaches stiffer material within a couple of metres.
A structure showing sudden movement (new wide cracking, doors bursting their frames, walls leaning or floors dropping) should be treated as unstable until an engineer says otherwise. Keep clear of the affected section, do not excavate beside distressed footings, and seek immediate structural advice.
Quote variables
What shapes the scope
Depth to competent founding material, which drives excavation volume per pin
Number of pins and the sequencing constraints the structure imposes
Groundwater and shoring requirements in each bay
Access for excavation, spoil removal and concrete delivery
Underpinning in NSW sits inside the residential building framework: it requires an appropriately licensed contractor, a structural design from a practising engineer, and geotechnical investigation proportionate to the site. Depending on scale and context it may need approval through a certifier or council. Verify licence, insurance details and the engineer's registration independently before work begins.
Underpinning systems
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