Drought causing house cracks is a well-established pattern across the Riverina, and Wagga Wagga’s climate makes it one of the most drought-exposed large towns in NSW. When the clay soil beneath a home loses moisture, it contracts. If the contraction is uneven, one section of footing drops relative to another and the structure above begins to show signs of distress. Understanding how this cycle works helps homeowners make better decisions about when to repair and when to hold off.
What drought does under your footings
Reactive clay works by expanding when it absorbs water and contracting when it dries out. The shrinkage is not trivial: on highly reactive clay of the kind common in the Riverina, the difference in volume between saturated and thoroughly dry soil can be significant enough to drop the surface by tens of millimetres. A footing sitting in that soil moves with it.
The problem is not uniform shrinkage across the whole site. If the soil under one corner of the house dries out faster than the rest, because that corner faces north, or has a garden bed that has been left unwatered, or is under the influence of a large tree pulling moisture from the ground, that corner drops while the rest stays put. This differential movement is what produces visible distress: cracking, sticking doors, sloping floors.
The relevant soil science is covered in more depth in our reactive clay soil guide for Riverina homeowners. The broader picture of how all foundation movement works in this region is in our guide to why foundations move in Wagga.
Why the worst cracking shows up in late summer and autumn
Soil moisture depletion is a slow process. Rain may fall in spring, replenish the upper soil, and the ground looks green and wet by October. But the clay at depth, below 600 mm or a metre, holds a moisture memory that takes months to dissipate in dry conditions.
As summer progresses and evapotranspiration draws moisture out of the upper soil, the depletion front moves downward. By February and March, a prolonged dry period may have driven soil moisture loss to depths that affect the footings. This is typically when the Bureau of Meteorology climate data for Wagga Wagga reflects sustained low rainfall months aligned with peak foundation complaint numbers across the region.
The lag between the driest conditions at the surface and the driest conditions at footing depth is why cracks often appear or worsen in late summer and early autumn rather than in the peak of summer heat. The soil takes time to dry to depth, and the footing responds once that drying front reaches it.
Conversely, when the rains return in autumn or winter, soil moisture recovery also takes months to reach foundation depth. Cracking that appeared in April may not begin to stabilise until June or July, even if rainfall has already returned.
Trees and drought: a double hit
Drought and trees near the house are a particularly damaging combination on reactive clay. A mature tree in full summer growth is pulling enormous quantities of moisture from the soil, sometimes hundreds of litres per day. On reactive clay, this creates a localised drying effect in the soil surrounding the root zone that goes well beyond what the weather alone would produce.
In a wet year the tree takes its water and the soil recovers quickly. In a drought year the tree continues pulling moisture even as the soil has less to give, and the drying effect at depth can be more severe than the drought alone would cause without the tree. This is sometimes called the combined moisture deficit: drought plus active tree roots both drawing from the same clay reservoir.
The tree species common in Wagga’s older residential areas, including large eucalypts, poplars and weeping willows, are particularly high water-use species. Our guide to trees near foundations in Wagga covers specific species and setback distances in more detail.
An important caution: removing a large established tree during or immediately after a drought can sometimes trigger the reverse problem. When a high-water-use tree is removed, the clay beneath it begins to rehydrate. On very reactive soil this rehydration can cause heave: the foundation rises rather than drops. In some cases this creates more damage than the original settlement. This is why tree removal near a foundation should involve professional advice, not just a chainsaw and a good intention.
Should you underpin during a drought or wait?
This is a genuine question without a single right answer, and it deserves an honest assessment rather than a simple prescription.
The case for waiting: If the cracking has appeared during a drought that is still ongoing, the soil movement may not have reached its endpoint yet. Underpinning while the soil is still drying means the underpin design is based on a ground condition that will keep changing. After the drought breaks and the soil rehydrates, further movement in the opposite direction (heave) may occur. In some cases, waiting until the soil moisture has stabilised gives a more accurate picture of the extent of damage and the repair required.
The case for underpinning promptly: If the movement is severe and the structure is at risk of progressive damage, waiting is not always practical. A cracked wall that is actively separating may reach a point where deferred repair costs significantly more than early intervention. Some damage is not safely staged.
The best time of year for underpinning guide covers the seasonal timing question in more detail. Our underpinning service page explains the repair options once you have made the decision to proceed.
In practice, an experienced professional assessing your specific situation will give better guidance than any general rule. The right answer depends on the rate of active movement, the structural condition of the building, and the forecast seasonal conditions.
Simple things to do in a dry spell to protect footings
Before spending on repairs, there are practical steps a Wagga homeowner can take during a drought to slow the soil moisture loss around the footings:
Maintain a consistent watering regime along the perimeter. This is not about keeping the garden green. It is about maintaining reasonably consistent soil moisture levels against the house walls so that the soil is not swinging to extremes while the rest of the site is dry. A slow, deep watering close to the house wall, once or twice a week during prolonged dry periods, can meaningfully reduce the moisture differential between the perimeter soil and the soil further out.
Check and clear downpipes. Blocked downpipes concentrate water runoff against the house during rain events and then deprive the perimeter of moisture between events. Keep water directed away from the structure but not so far away that the perimeter soil dries out completely.
Avoid turning off drip systems or bore pumps to garden beds adjacent to the house. When a garden is removed or neglected during a drought, the moisture that was being added by irrigation is no longer present. This can accelerate perimeter soil drying.
Our drainage and moisture correction service can assess whether your site’s current drainage and moisture management is contributing to movement.
FAQs
Does drought always cause foundation damage?
Not always. A drought affects footings most when the soil is reactive clay, when the footings are relatively shallow or are already marginal, and when the moisture loss is uneven across the site. Homes on less reactive soils, or on footings that penetrate to stable depth well below the zone of moisture fluctuation, can experience prolonged droughts without significant distress.
Why does my house crack every summer but the cracks partly close in winter?
This is the classic seasonal cracking pattern on reactive clay: the soil dries out in summer and compresses, dropping the footing slightly and opening cracks; the soil rehydrates in winter, partially recovering the lost volume and partially closing the cracks. If the cracks close fully and the house returns to its original condition each year, the total movement may be within a tolerable range. If each year the cracks close less completely than before, cumulative damage is accumulating.
Is it safe to live in a house that is cracking due to drought?
In most cases, yes. The type of cracking associated with drought-induced differential settlement is typically gradual and the structure retains its load-bearing capacity throughout. The exception is if cracking is severe or rapid enough to compromise structural connections, which is uncommon in typical residential cases but not impossible. If you are in any doubt about safety, get a professional assessment rather than relying on a general guide.
Will my cracks close again when it rains?
Partly, possibly. If the movement was driven by soil drying, rehydration of the soil will cause it to partially recover volume and may reduce visible cracking. However, the recovery is rarely complete, particularly after severe or prolonged drought. Each cycle tends to leave some residual movement that does not recover. This is why houses in Wagga with many drought cycles behind them often show an accumulation of crack history rather than a clean reset each winter.
How do I know if my drought cracking needs professional attention?
Monitor the cracks as described in our soil heave vs settlement guide and note whether they are growing. A crack that reaches 2 mm or wider, or that shows visible displacement between its two faces, warrants professional assessment rather than monitoring alone. If doors and windows have started sticking in the same period, add that to the assessment. Contact us for a free quote if you want a professional opinion.