Subsidence is a phenomenon that occurs when the ground beneath a property sinks, causing the building’s foundations to shift and crack. If left unchecked, subsidence can lead to major structural damage that may be costly to repair. For homeowners, identifying the signs of subsidence early is essential to preventing these minor issues from escalating into major problems.
To identify subsidence in your home, look for signs such as diagonal cracks in walls, uneven floors, and sticking doors or windows. Address these issues by seeking professional advice, as early detection can prevent severe structural damage. Solutions like underpinning or tree root management may be required.
This blog will help you recognise the warning signs of subsidence, understand the underlying causes, and provide guidance on addressing the issue before it worsens.
What is Subsidence?
Subsidence occurs when the ground beneath a building moves, usually in a downward direction. This movement can result from changes in the soil’s moisture content, shifting groundwater levels, or the removal of supporting materials from under the foundation. The structure shifts along with the ground, which could result in uneven flooring, misaligned doors and windows, and wall fractures.
Subsidence is often confused with heave, which is the opposite movement of the ground pushing upward. Both can cause significant damage to a property, but subsidence is more common and, when left untreated, can lead to long-term structural problems.
Properties most at risk of subsidence are those built on clay-rich soils, where fluctuations in moisture levels can cause the ground to shrink or swell. Additionally, homes near large trees or older properties with shallow foundations may be more vulnerable. Recognising signs of subsidence early can help you act before more serious damage occurs.
Common Signs of Subsidence
The sooner you identify the signs of subsidence, the more likely you can take corrective action to prevent further damage. Some of the key indicators include:
- Cracks in Walls
Cracks are one of the most noticeable signs of subsidence. Unlike minor hairline cracks caused by normal settling, subsidence cracks tend to be wider (over 3mm) and diagonal, typically starting near windows, doorways, or corners of rooms. These cracks often indicate that the building is shifting due to the ground moving beneath it.
Subsidence cracks can appear inside or outside the home. Externally, cracks in the brickwork are a red flag, especially if they run through the mortar. Over time, these cracks may widen, making them more obvious and more concerning. - Doors and Windows Sticking
When subsidence occurs, it can cause the structure to become uneven. This unevenness often affects door and window frames, causing them to become misaligned. If your doors or windows begin to stick or jam unexpectedly, or if you notice gaps forming around the frames, this could be an indicator that subsidence is affecting your home’s foundation. - Uneven or Sloping Floors
Another potential sign of subsidence is when floors become uneven or start to slope. While many older homes may have a slight slope due to settling, sudden or pronounced changes in the level of your floors can suggest a shift in the foundation. If you notice that certain areas of your home are starting to feel “off-balance,” it’s time to investigate further. - Gaps Around Window Frames and Doorways
As subsidence progresses, gaps may form around windows and doorways. This is a direct result of the building shifting as the foundation moves. These gaps may not only cause aesthetic issues but can also impact the energy efficiency of your home by allowing drafts and moisture to enter. - Cracks in External Brickwork
If cracks are visible in the external brickwork, particularly if they are diagonal or run through both bricks and mortar, it’s a strong sign that subsidence is present. Such cracks often start small but can expand quickly if the underlying cause is not addressed.
Minor Subsidence Cracks vs. Major Structural Damage
It’s important to distinguish between minor subsidence cracks and more serious structural damage. Minor subsidence cracks tend to be small and superficial, typically less than 3mm wide and do not indicate significant structural movement. These cracks may be caused by natural settling and can often be repaired without concern.
Major structural damage, however, is characterised by larger cracks that continue to widen over time. If cracks run through both the internal plaster and external brickwork or if you notice significant shifting in your home’s floors, doors, or windows, it’s a clear indication that subsidence is present and likely to worsen without professional intervention.
Causes of Subsidence
Understanding the causes of subsidence is crucial to preventing it from happening in the first place. Here are some of the most common causes of subsidence:
- Soil Composition
Properties built on clay-rich soils are particularly susceptible to subsidence. Clay soil expands and contracts significantly depending on moisture levels. In dry periods, the clay shrinks, leading to gaps and voids under the foundation. During wetter periods, the soil swells, potentially causing upheaval. This cycle of expansion and contraction weakens the ground and can cause subsidence over time. - Tree Roots
Large trees planted too close to a property can also contribute to subsidence. Tree roots absorb moisture from the soil, particularly during dry periods. This can exacerbate the shrinking of clay soil, pulling the ground away from the foundation. Willows, oaks, and poplars are particularly notorious for causing subsidence due to their extensive root systems. - Water Damage
Leaking drains, burst pipes, or poor drainage systems can wash away the soil beneath your property, leaving the foundation unsupported. This can lead to subsidence if the soil becomes too waterlogged or if voids develop underneath the foundation. Ensuring your drainage systems are functioning properly is a key factor in preventing subsidence. - Changes in Groundwater Levels
Groundwater levels naturally fluctuate over time. However, significant changes, often caused by nearby construction or geological shifts, can cause the ground to sink. In areas with high groundwater levels, prolonged periods of drought can cause the ground to dry out, while heavy rainfall can result in the soil becoming waterlogged, creating instability beneath a property’s foundation. - Shallow or Poor Foundations
Older properties, especially those built before modern construction regulations, often have shallow foundations. These foundations are more susceptible to movement, particularly if they were not designed to account for the specific soil type or environmental conditions of the area. In some cases, the foundation may not extend deep enough to reach stable ground, increasing the risk of subsidence.
How to Confirm Subsidence
If you suspect subsidence in your home, it’s important to seek professional advice. While you can identify many of the early signs of subsidence yourself, a professional chartered building surveyor can confirm whether the damage is due to subsidence and recommend appropriate solutions.
- Monitoring Cracks
Surveyors use specialised tools to monitor cracks over time. This process involves placing measuring devices over the cracks to determine whether they are expanding. If the cracks are growing, this is a clear indication that subsidence is occurring. - Soil Investigations
A soil investigation can provide valuable information about the condition of the ground beneath your home. By taking soil samples from around your property, a surveyor can determine whether the soil is prone to shrinking or swelling, which may be contributing to subsidence. - Level Monitoring
In cases where uneven floors or misaligned doors and windows are present, a surveyor may use level monitoring to assess whether parts of the building are sinking at different rates. This involves placing sensors at various points around the home to track any shifts in the building’s elevation over time.
Addressing Subsidence: What to Do Next
Once subsidence has been confirmed, it’s essential to address the issue as soon as possible. Ignoring subsidence can lead to further structural damage and increase the cost of repairs.
- Underpinning
Underpinning is one of the most common and effective methods for addressing subsidence. This process involves strengthening the existing foundation by extending it deeper into more stable soil. Underpinning is a long-term solution, but it can be expensive, and the method used will depend on the severity of the subsidence and the type of soil beneath your property. - Tree and Root Management
If trees are contributing to the subsidence, tree root management may be required. This can include trimming or removing large trees that are too close to the property, installing root barriers to prevent further damage, or managing the water supply to the trees to reduce their impact on the soil. - Drainage Repairs
Leaking pipes or poor drainage can worsen subsidence by washing away the soil beneath the foundation. If water damage is contributing to the problem, repairing or replacing the affected drains is essential. In some cases, improving the overall drainage system around the property may help prevent future issues. - Foundation Repairs
In more severe cases, structural repairs to the foundation may be necessary to stabilise the property. This can include replacing damaged sections of the foundation, reinforcing weak areas, or installing pilings to provide additional support.
Preventing Future Subsidence
While subsidence can be costly to repair, there are steps you can take to prevent it from occurring in the future:
- Monitor Tree Growth
Ensure that large trees are planted at a safe distance from your home. Regularly prune trees and shrubs to prevent excessive root growth, which can deplete moisture from the soil and cause subsidence. - Maintain Proper Drainage
Ensuring that your property has an effective drainage system is crucial in preventing water damage. Regularly inspect your gutters, drains, and pipes to identify and repair any leaks that could lead to soil erosion. - Avoid Overwatering
In clay-heavy areas, avoid overwatering your garden, as this can over-saturate the lawn. When this occurs near your property’s foundation, it can cause soil saturation and lead to instability. Proper irrigation techniques can help maintain balanced moisture levels in the soil, reducing the risk of subsidence. - Regular Property Inspections
Conducting regular inspections of your property can help you spot early signs of subsidence before they become serious. Pay attention to cracks in walls, uneven floors, and changes in doors or windows. After periods of heavy rainfall or prolonged dry weather, these inspections become even more critical.
Conclusion
Subsidence is a serious issue that can lead to costly repairs if left unchecked. However, by recognising the signs of subsidence early—such as subsidence cracks, sticking doors and windows, and uneven floors—you can take swift action to address the issue. Whether it’s caused by tree roots, poor drainage, or clay-heavy soil, understanding the root cause of subsidence is key to finding the right solution.
If you suspect that your home is experiencing subsidence, it’s essential to consult a professional surveyor for a thorough inspection. From underpinning to tree management, there are several ways to fix subsidence and prevent further damage to your home. By maintaining your property’s drainage systems, monitoring tree growth, and conducting regular inspections, you can reduce the risk of subsidence and protect your home from costly structural damage.If you need professional guidance or a subsidence assessment, don’t hesitate to contact Simmons Taylor Hall. Our team of experienced chartered surveyors is ready to help you safeguard your home and provide expert advice on addressing subsidence.
