Dubbo's clay swells wet, shrinks dry, and houses move with it. Cracks open through a dry spell, doors jam in winter, a gap grows under the skirting. We fix that by underpinning: getting under the footing, with concrete piers or injected resin, and taking the movement out of it. We do it from South Dubbo and Delroy Park to Keswick. Say which wall, and since when.
Get a Quote →A footing is the concrete strip a wall stands on; underpinning is new support built beneath it once the soil stops carrying the weight. Much of Dubbo sits on heavy, reactive clay, commonly classified as highly reactive (Class H1 or H2) under Australian Standard AS2870, though the classification for any given block is set by a site-specific geotechnical investigation. Reactive means it swells and shrinks as its moisture changes: tens of millimetres between a dry spell and a wet stretch, far more than most of coastal NSW ever deals with.
The crack is the symptom. The cause is that moisture changing, up or down: a leaking downpipe, a garden bed watered against the wall, a run of hot months. One footing moves, the next does not, and the wall between them cracks. An engineer's level survey comes first, mapping the movement footing by footing, then drainage and soil classification as the likely driver. Where the groundwater is salty, the concrete mix has to suit it, since salt works on concrete and the steel inside it.
Resin injection is for moderate movement: an expanding polyurethane resin pumped in from outside packs the voids the dry clay left and eases the footing up again. Concrete piers are for the severe cases: we dig beneath the footing and pour new concrete that reaches past the reactive zone, often deeper piers than you'd need on more stable ground.
Neither job normally means moving out. Resin means no pits, just drill holes along the outside wall and a lift you only see on the level. Piers take longer: the ground along the dropped wall is opened in short runs, each one hardened before the next, so the wall stays held up between. We have seen Dubbo houses patched and cracked again, so finding where the water gets in, or out, comes with the job.
Fast, low-disruption footing lift and stabilisation using expanding polyurethane resin, suited to moderate movement on Dubbo's reactive clay.
Deeper excavated concrete piers taken past the reactive clay zone, built to handle Dubbo's wide shrink-swell range.
Level surveys and soil classification checks to confirm the extent of reactive movement before recommending a fix sized for it.
Checking irrigation, drainage and nearby trees, the biggest levers on how much a reactive clay site actually moves season to season.
Dubbo Regional Council's 2017 brochure 'Salinity in Your Backyard' names the Troy Gully catchment, including the Richmond, Eastridge and Boogadah estates, as a long-standing salinity target, and reports salinity in Firgrove Estate, the CBD, South Dubbo and Delroy Park. It also shows homes and offices with salt damage in South and Central Dubbo, including a groundwater tide mark on a South Dubbo wall. Brick or render breaking down at the base of a wall can be salt attack rather than, or as well as, footing movement, and each needs a different repair.
Ground conditions also change across the city, and even within one estate. The former Dubbo City Council's Urban Salinity Implementation Plan, filed on the NSW Planning Portal in 2020, rates the CBD, Troy Creek Constriction and Eulomogo Estate as 'Very High' salinity hazard, and South Dubbo, Richmond Estate and Orana Heights as 'High', from an April 2010 assessment. Council's 2020 Daisy Hill DCP puts groundwater deeper than 10 m across most of Daisy Hill, but only 1.4 m below the surface in its central northern section.
Where a house sits can change how deep new piers go and what concrete goes in. For infrastructure in Daisy Hill, that DCP requires concrete strength and reinforcement cover to follow AS 2870 for aggressive soils, with site testing to confirm the exposure class. Ask whoever designs the underpinning whether the same applies under your house. Readings from Council's 129 groundwater monitoring bores across the urban area are available at cost from its Sustainability Coordinator.
Underpinning and footing repair enquiries are welcome from across Dubbo, including South Dubbo, West Dubbo, Central Dubbo, Delroy Park and Keswick, the Richmond, Eastridge, Boogadah and Firgrove estates, and the Daisy Hill estate on Eulomogo, Pinedale and Torwood roads. Enquiries from villages in the wider Dubbo Regional Council area, such as Ballimore and Wongarbon, are welcome too. If your area isn't listed, send the enquiry anyway and say where the property is.
Tell us what you need and where the property is.