Underpinning FAQ — Tamworth

It comes down to scope. Resin injection under a few sections is a smaller job than underpinning several footings, and both sit well below a full-perimeter underpin. Depth, soil, access and the number of piers set the price, and an engineer's level survey shows which footings have actually moved, so you only pay to underpin those. Tamworth Regional Council's DCP 2010 lists highly reactive and saline soils among the constraints a housing design must consider, so ask whether the engineer's design rests on soil testing, which may be a separate cost. Get the engineer's report before any quote so the price covers the cause, not just the symptom.

Hairline cracks under 1 mm that don't grow are usually cosmetic. Cracks wider than 5 mm, diagonal cracks running from the corners of doors and windows, doors or windows that have started binding, and cracks that come back after patching are worth an engineer's look. Photograph each crack with a ruler in shot and note the date, then check it again after a dry spell and after a wet one. Bureau of Meteorology averages for Tamworth Airport make April the driest month and November the wettest. Movement that follows the weather points to reactive soil.

HydroSpatial's March 2023 report for Tamworth Regional Council's City Wide Floodplain Risk Management Study and Plan recommended a voluntary house-raising scheme for 67 houses. Each met the report's threshold of 0.3 m of above-floor flooding in a 1% AEP flood (a flood with a 1% chance of happening in any year). Under the 2022 NSW Department of Planning and Environment guidelines the report cited, house-raising funding was limited to homes approved and built before 1986. In December 2025 the Inverell Times reported a Council manager saying the 2023 modelling had a glitch, and revised modelling showed lower projected flood levels. Flood levels feed into floor heights and footing design, so ask Council which level applies to your address.

Almost never. Underpinning is done a section at a time from outside or under the house, so you can usually keep living there through the job. Expect noise and vibration while each section is dug out and poured, and parts of the yard will be off limits while a section is open. Ask the contractor how the work will be staged so you know which areas will be affected and when.

Resin injection pumps expanding polyurethane resin under the footing to fill voids and lift it back closer to level. It is quicker, less invasive and usually cheaper, and suits moderate movement. Concrete underpinning means digging below the existing footing in stages and pouring new, deeper piers or a beam underneath. It is the heavier fix for severe movement, or where the engineer wants the footing taken past the soil that is moving. The engineer's report, and the soil information behind it, should decide which one your house needs.

Underpinning supports the footing, but on reactive clay it may not hold if the moisture problem underneath is left alone. Sort out drainage, keep garden beds and irrigation back from the foundation line, and deal with tree roots close to the house. Ask the contractor for drainage recommendations as part of the same job, because underpinning without fixing the water source is a common reason repairs fail. Once the movement has stopped, the existing cracks can be patched.