What does a sinking floor or concrete slab mean?

Sinking concrete floors or slabs are an indication of building subsidence (when the ground sinks due to movement of underground material).

A building can sink at various points or the collapse can be spread across the entire footprint of the foundation or slab, depending on where the affected ground is and how large an area it is. This can be very serious, and if left untended is likely to worsen, creating further building subsidence and other consequent damage.
Our bespoke solutions for slab lifting and re-levelling address the underlying problem of subsidence by strengthening the ground beneath. Our level correction methods can cater to any building size, from homes and driveways to warehouses and transport yards, and are non-invasive, cost-effective, time-efficient, with minimal disruption to the occupants.

How much does subsidence repair cost?

Get a FREE house assessment in 3 simple steps:

Step 1:

Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.

Step 2:

Our friendly customer service team will be in touch to schedule a site assessment that suits you.

Step 3:

One of the Mainmark experts will visit your home or property, assess the damage, and ascertain the likely cause. They will establish the approach needed, creating a plan specific to the needs of your building and provide you with a detailed quote.

Before remediation

Gap between floor and wall in a house, before remediation from Mainmark

After remediation

Gap between floor and wall in a house, after remediation from Mainmark

Sinking floors in homes

Mainmark’s level correction methods which include concrete floor lifting and ground re-levelling are effective on buildings of any size, including residential homes. They also deliver successful results on driveways and paths. We have successfully re-levelled thousands of projects around the world.

If you have a sunken floor, you may need ground re-levelling. We visit your home, assess 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 building and its 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 concrete floor lifting and repair solutions are cutting edge and the modern answer to the traditional way to underpin; it is like keyhole surgery compared to concrete underpinning. Our ground re-levelling 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 slabs and driveways

What causes subsidence?

There are many different causes of subsidence and various contributing factors. All involve some sort of change in the ground, which, in turn, generates movement of the soil. For example, droughts dry the ground, resulting in the soil (especially clay) contracting. Seismic activity shakes the ground, often resulting in liquefaction which ‘squeezes’ liquid up from the ground. Excavation and construction, even heavy traffic and machinery vibration, can move, displace and alter the condition of the ground.

As well, different types of ground are more affected by different conditions. For example; clay is particularly prone to contracting in drought conditions, gravel and stony grounds can be more affected by nearby excavation, and excess water has a softening effect on dirt. Subsidence can happen over large areas of land or in a small targeted area. It can occur over a lengthy period of time, or can be an immediate reaction to nearby activity or natural events. When ground has been affected, building subsidence is common. Foundations or footings are no longer ably supported, sinking due to weak ground.

Likely causes:

Water flooding the ground

Drought drying out soil

Washaways from broken pipes (such as water, sewer, stormwater drainage)

Poorly compacted fill

Liquid, gas or mineral resources being removed from the ground

Earthquake and seismic activity

Tree roots can suck moisture from the ground

Vibrations caused by heavy road traffic or by machinery

Absence of an organised footing system – in very old buildings or in buildings with additions or alterations

Nearby excavation

Heavy loading

Deterioration of retaining walls

How to fix sinking floors?

The only way to fix sinking concrete floors and slabs is to raise foundation, re-level and re-support the building. Mainmark specialises in concrete levelling. Level correction not only re-levels a building, but also strengthens any weak ground under and around the perimeter of the foundations, ensuring a stable base and helping to avoid any recurring sinking issues. Traditional level correction or “underpinning” methods involve excavating or digging up parts of the foundation, pouring in concrete, waiting for it to set and then jacking up the building off the concrete blocks. This method can be:

  • time consuming (often requiring weeks or months)
  • messy
  • usually means you’ll have to vacate part or all of the building while tradespeople work

Mainmark methods are much friendlier, both to the building and to those that occupy it. Our non-invasive concrete re-levelling techniques are cost and time efficient.

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

Benefits of Mainmark’s level correction methods:

Floors and buildings are brought back to level and sunken floors and slabs are corrected

Cracks in walls generally close up

Jammed doors and windows are freed up

We don’t make mess: there is no concrete dust, water, or anything else to clean up

There is minimal disruption

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

With simple jobs, residents can 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 very quick, completed in a fraction of the time of traditional methods, and simple residential work is often done in a day

The methods we use strengthen weak ground, so your home becomes level and more stable

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

Mainmark level correction 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.