Stumps / piers
Vertical posts (timber, concrete, or brick) supporting bearers under a raised timber floor.
Stumps transfer the floor load to the ground. Timber stumps are common in older Adelaide homes; concrete stumps were used from the 1950s onwards; brick piers are typical in heritage homes.
Failure modes: timber stumps rot at ground level (the most common failure point), settle into soft soil, get attacked by termites. Concrete stumps can crack or tilt. Brick piers can fail if mortar erodes.
Restumping is one of the most disruptive repairs - it lifts and re-supports the floor. Costs can run from a few thousand for partial replacement up to $30,000+ for a full restump on a large home.
Bearers and joists
The horizontal timber members supporting a raised timber floor. Bearers sit on stumps/piers; joists sit on bearers; floorboards sit on joists.
Footing movement
Movement of the building's foundations, usually caused by reactive soil, water entry near footings, or undersized original footings.