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Sinking Floors & Slabs

A sign of subsidence

What does a sinking floor or concrete slab mean?

Sinking concrete floors or slabs are an indication of building subsidence

If you notice gaps where your walls meet the floor, you might have a sinking or damaged foundation. Sinking concrete floors or slabs are a warning sign for serious and ongoing structural damage caused by subsidence. 

Mainmark offers bespoke solutions for slab lifting and re-levelling. These solutions address subsidence issues by strengthening the ground beneath your home.

Our level correction methods can cater to any building size, from homes and driveways to warehouses and transport yards. These methods can be non-invasive, cost-effective, and time-efficient.

Repair sinking floors caused by movement

Understanding Sinking Floors: Subsidence Causes and Factors

The issue of subsidence, especially in the context of sinking floors, stems from a multitude of causes and contributing factors. All of these share a common thread—a shift in the ground, resulting in soil movement.
Moreover, the impact varies depending on the type of ground involved. When the ground undergoes changes, building subsidence becomes a prevalent concern.
In such cases, foundations or footings lose their full support and begin to sink due to the weakened ground.

Expansive Soils

A contributing factor to sinking floors is irregular soil behaviour. For example, soils containing reactive clay can expand or contract throughout the year. Rainy seasons will lead to soil expansion from moisture, while contraction occurs in the warm, dry conditions of hotter months. 

These fluctuations could be regular, or the soil may expand and contract unevenly. This causes stress to the foundations of your home, which could lead to internal and/or external wall cracks. This will be of particular concern as more parts of the country experience extreme weather events year on year.

Tree Roots

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

Poor Drainage

One major contributor to sinking floors is issues with drainage. Pipes left unconnected, broken drains and other leakages can mean water drains into the soil under your home. This erodes the soil over time, leading to ground instability. 

The soil under your home could also suffer from aeration, or voids could form. This eventually leads to ground instability, which causes wall cracks.

House Extensions

Sinking floors can appear when the weight of your home increases beyond the foundation’s capacity. Wall extensions or other extra loads increase the weight of the house, as well as increasing the force exerted on the foundation and the soil it sits on.

As with soil expansion, uneven direction or distribution of this force can put stress on the structure. Wall cracks in this case might be the start of more serious issues.

Extreme or Seasonal Weather

Natural disasters such as flooding, drought and earthquakes affect soil moisture levels in particular clay resulting in excessive foundation movement.

Renovation or Construction

Vibration caused by nearby construction activity such as drilling or piling, or heavy road traffic causes soil particles to shift and settle, resulting in ground subsidence.

Expanding Materials

Expanding materials can also cause wall cracks. Some clay bricks expand as they age, increasing up to several millimetres per year in some cases. Concrete is another material that can contract or shift over time. These changes can cause wall cracks unless properly controlled. 

Trust The Experts

Mainmark provides an alternative to traditional underpinning.

Our non-invasive, engineered solutions improve the ground beneath existing buildings.

Ground improvement enables the foundations to carry greater loads. It also reduces how much settlement or moving happens across your house from season to season. Our Teretek or Permeation Grouting technologies can be used for ground improvement in suitable soils.

If your house has experienced sinking, our re-levelling solutions can raise your house back to level. We can also carry out ground improvement to mitigate further damage. Mainmark developed Teretek and JOG technologies, which are versatile and suitable for re-levelling both simple and complex structures.

Mainmark’s re-levelling and void filling technologies can also work alongside traditional underpinning. For example, you may need to widen the foundation or install piling. In some cases, your house may need to be re-leveled before installing these underpinning solutions.

Sinking Floors Inside Your Home

If you see signs that your floors are sinking, this could mean the entire structure of your home is also sinking. Sinking floors and concrete slabs indicate that pressure is being exerted on your home.

Over time, this pressure can lead to serious and ongoing structural issues. You may notice other signs in your home, such as wall cracks, cracks in your cornices and ceiling, jamming windows and doors, sloping floors and more.

Foundation re-levelling is essential to mitigating these structural issues from occurring, and to stop further structural damage.

Sinking Floors Outside Your Home

You may also notice sinking or gaps in concrete slabs outside your home, such as in your driveways, paths and patios. If these outdoor areas are experiencing sinking, it could also indicate deeper issues underground.

The risks outside can vary, but include damage to underground wiring or services, drainage breaks or leaks, and other safety hazards. 

Re-levelling your concrete here is key to ensuring a safe, functioning, and aesthetic outdoor space.

Before & After

Residential Sinking Floor & Slab

Our Teretek®Resin Injection technology can raise, re-level and re-support sinking floors and slabs.

 Watch how our non-invasive, cost-effective technology raises and re-levels a sinking residential floor.


Mainmark’s Level Correction Methods Are:


Our technologies have fast curing times and treated areas can be used immediately or without the delays compared to traditional repair methods.

Environmentally Inert

Our technologies use an inert material that is non-toxic and does not leach into the environment or affect the treated area.


Our solutions are of surgical nature compared to traditional methods.


Compared to traditional methods, our solutions are more cost-effective.

Get a quote

Arrange a site 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.

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© 2024 The Mainmark group of companies. ‘Mainmark®’, ‘Terefil®’, ‘Terefirm®’ and ‘Teretek®’ are trademarks of the Mainmark group of companies.

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