Definition of subsidence

The ground beneath us is constantly shifting.

icon of a house with cracked wallsSubsidence is the propensity for upward, lateral, or downward ground movement, which can result in structures moving, sinking in one area or across the entire foundation footprint. During construction, ground instability can cause soil slippage which often requires stabilisation prior to conducting additional excavation for building foundations or swimming pools or building retaining walls. Once a building is already in place, ground instability can cause movement of the building or structure, resulting in internal or external wall cracks, inability to open and close windows and doors, sunken floors, and more.

Equally, weak ground cannot adequately support the weight of structures, thereby causing subsidence. Uneven floors, fractured floor tiles and wall cracks are all strong indicators of weak ground beneath the structure.

If a building or structure has subsided due to ground instability or weak ground, it is important to fix it right away, or risk further damage and potential hazards.

Download Our Guide to Subsidence

Ground instability and weak ground under homes

Mainmark offers state of the art technology to stabilise the ground beneath your home. Using resin injection ground stabilisation, we improve ground compaction. We can then raise and re-level sunken buildings, then add support to the ground for soil stabilisation to strengthen the foundation and stop the soil underneath and around the buildings slipping or moving. We have successfully raised, re-levelled, and re-supported thousands of homes around the world.

We visit your home, assess the damage, and discover the cause. Our experienced engineers and technicians establish the approach needed, creating a plan specific to the needs of your house.

As the weak ground under houses is strengthened, and sunken floors are brought back to level, any internal and external wall cracks generally close up too. Most importantly, structural damage is resolved and, with a stable foundation, the future of the house is sound.

Our deep resin injection ground stabilisation and foundation repair solutions are the modern answer to more traditional methods of underpinning. Compared to concrete underpinning, it’s like keyhole surgery, as the injection holes are often as small as the size of a five cent coin. Our alternatives to underpinning are not just for concrete floors. We can underpin, raise and re-level strip footings, raft slabs, and ‘waffle-pod’ slabs too.  We also have solutions for soil stabilisation and ground compaction under driveways and paths.

Deep-lift using our Teretek engineered resin solution is a method used for strengthening foundation ground. The resins and hardeners mix together in the ground, and expand to compact the adjacent soils and increase their load-bearing capacity.

Another of our technologies for improving ground compaction and stability is Permeation Grouting, which can create ground cohesion before soil excavation takes place, making it a good option for soil stabilisation for swimming pools, retaining walls etc. It involves filling in cracks, joints, and other small defects in rock, sandy coastal, and other non-cohesive soils or other porous ground with a cement-based grout. It can stabilise the ground at depths of up to 60 metres.

What causes weak ground and subsidence?

Subsidence can happen naturally as part of the earth’s constantly shifting crust. It can be exacerbated by issues such as soil compaction, loss of ground moisture, excessive excavation, or erosion. Ground instability causes subsidence and, often, the damage can seem to be reversed as the ground shifts back and forth over time.

Soil Types:

Clay soil can shrink, crack and shift during hot weather, and then expand during wetter weather. After a drought, sandy or fine gravel soil is much drier, and moves more easily which can impact building footings.

Excess Water:

Leaking drains and water mains or burst water pipes can wash away or soften soil, causing it to compact under the foundation weight.

Tree Roots:

Neighbouring trees and shrubs absorb water using their roots causing movement in the soil as it soaks up moisture in the ground and grows.

Extreme & Seasonal Weather:

Natural disasters such as flooding, drought and earthquakes affect soil moisture levels in particular clay where it compresses and expands resulting in excessive foundation movement. Erosion is another natural cause.

Footing Systems:

Flawed foundation design or inadequate compaction of soil during construction results in movement of the structure as it settles. Older properties may have shallower footings and foundations hence greater movement.

Renovation or Construction:

Vibration caused by nearby construction or machinery activity such as drilling or piling, or heavy road traffic causing soil particles to shift and weaken the ground.
Liquid, gas or mineral resources being removed from the ground affecting stability, can cause voids and sink holes.

computer screen with Typical signs of subsidence

Want to learn more about the signs of subsidence?

Explore our interactive house and view typical subsidence problems around your home

Sinking floors, paths and driveway slabs, cracked walls, jamming doors and windows can all be indicators of structural damage due to subsidence and voids under the ground. Typical causes are unstable or weak ground, a broken pipe causing soil erosion, moisture changes in clay soil, nearby building and excavation works, and seismic activity or liquefaction. Our solutions are cutting edge and the modern answer to the traditional way to underpin; they are like keyhole surgery compared to concrete underpinning. Our alternatives to underpinning are not just for concrete slab floors. We can underpin, raise and re-level strip footings and raft slabs, plus we can infill under slabs and driveways.

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How to fix subsidence?

Mainmark specialises in soil stabilisation and ground compaction, foundation repairing, and strengthening weak ground to improve support for buildings, roads, bridges and other on-ground structures. We treat the ground beneath them to raise, re-level, and re-support these structures.

There are a number of options available to stabilise the ground, such as soil and embankment stabilisation, and void or hole-filling.

For example, Mainmark’s Terefil is the most advanced structural lightweight polymer modified cementitious-based filler. It flows into spaces to fill voids, making it a fast and effective way to stabilise the ground. Compared to typical foams, the patented foam used in Terefil has increased stability, a greater lift thickness, and can be pumped greater distances. It’s a cost-effective and environmentally-inert option that suits a range of applications such as mass fill for large voids, tanks, and abandoned mines.

Permeation grouting can create ground cohesion before excavation. It’s the longest-established and most widely-used technique, which involves filling cracks, joints, and other small defects in non-cohesive soils, sand, or other porous media. It can stabilise the ground at depths of up to 60 metres.

Alternatively, Mainmark can inject our proprietary Teretek engineered resin solution into the foundation ground under a building’s footings. The resins expand together chemically, creating pressure. That pressure lifts the building back to its correct level. Then, if there are weak layers in the ground, continuing injection at deeper levels can resolve this by compacting the ground, densifying and strengthening it to increase its bearing capacity. In some soil conditions, Mainmark can increase the bearing capacity of weak strata by as much as 500 per cent.

In cases of weak ground, Teretek engineered resin also assures sub-grade stability under existing on-ground structures including buildings, concrete floors, driveways, roads, paved airport runways, bridge approach slabs, bridge abutments and more.

Mainmark’s methods are quick, precise, don’t leave a mess, and don’t generally require occupants to vacate a building while work is being done.

Various product warranties and Building Code requirements apply (please contact us to see which apply to your region or country).

Benefits of Mainmark’s soil stabilisation methods:

Can be carried out at one or more depths; as deep as 14 metres under the surface for resin, or 60 metres for permeation grouting

Can increase the bearing capacity of weak strata under structures by up to 500 per cent

Can be used to prepare structures that need to support increased loads, e.g. when there is to be an addition to the building itself

There is little if any mess: no dust, water, or other materials to clean up

There is minimal disruption to your daily life

We don’t cause further damage to the house or landscaping

With simple jobs, residents can often stay in the home and may not even need to move furniture

Techniques are non-invasive: we don’t tear up floors or excavate ground

Our methods are fast, completed in a fraction of the time of traditional methods, so we can often complete your project in as little as one day

The products and techniques we use have zero negative impact on the environment

Mainmark ground stabilisation and strengthening methods used on homes:

For expert advice on identifying the causes of movement in a building, download a copy of ‘Foundation Maintenance and Footing Performance: A Homeowner’s Guide’ from CSIRO.