Subsidence is a term that many homeowners dread hearing. It refers to the gradual sinking or settling of a building’s foundation, which can cause serious structural problems if left unaddressed. Understanding what subsidence is, why it happens, and how to identify it early can help you take the necessary steps to protect your property.
In this blog post, we’ll explain subsidence in detail, discuss its common causes and signs, and offer advice on what to do if you suspect your property is affected.
What is Subsidence?
Subsidence is the downward movement of the ground beneath a building’s foundation. When the soil shifts, it can cause parts of the building to sink, which results in structural stress and damage. Unlike settlement, which is the natural, gradual sinking of a building over time, subsidence is often sudden and uneven, leading to cracks and other visible damage.
Subsidence can be particularly problematic for buildings with shallow foundations and is more common in areas with certain soil types, such as clay.
Common Causes of Subsidence
Several factors can contribute to subsidence. Here are some of the most common causes:
- Soil Type
Clay soils are especially prone to subsidence, as they expand when wet and shrink when dry. This swelling and shrinking can cause the ground to move, leading to foundation problems. - Tree Roots
Trees and large shrubs planted too close to a property can absorb significant amounts of water from the soil. This can lead to soil shrinkage, especially during hot, dry weather, which in turn causes the ground to sink. - Water Leaks
Leaking pipes or drains can wash away soil around the foundation, making it unstable. Over time, this can lead to the ground shifting and cause subsidence. - Drought and Hot Weather
Prolonged periods of dry weather can cause soil to dry out and shrink, especially in clay-rich areas. This shrinkage reduces the ground’s ability to support a property, leading to subsidence. - Poorly Built Foundations
Properties with shallow or poorly constructed foundations are more vulnerable to subsidence, as they may not be adequately supported by the ground below. - Groundwater Levels
Fluctuations in groundwater levels, particularly during prolonged dry spells, can destabilise the soil supporting your foundations and trigger subsidence. - Man-Made Factors
Nearby mining activity, construction work, or the removal of supporting structures can disturb the ground and contribute to subsidence.
Signs of Subsidence
Identifying the signs of subsidence early can help you take action before the problem worsens. Here are some common indicators:
- Cracks in Walls: Cracks associated with subsidence are usually diagonal, wider at the top than the bottom, and can appear near doors or windows. They are often more than 3mm wide.
- Doors and Windows Sticking: Subsidence can cause door and window frames to become misaligned, making them hard to open or close.
- Sloping Floors: A noticeable slope in the floor may indicate that part of the building is sinking.
- Gaps between Walls and Woodwork: Gaps can form between walls and door frames or skirting boards as the building shifts.
- External Cracks: Subsidence may also cause visible cracks in external walls or the ground around the property.
If you notice any of these signs, it’s important to consult a professional surveyor to assess the extent of the damage.
How to Confirm Subsidence
If you suspect subsidence, it’s important to get a professional opinion rather than rely on the visible signs alone. A RICS-accredited subsidence surveyor can provide a definitive diagnosis, typically through:
- Initial Inspection: A surveyor carries out a visual inspection to identify the signs of subsidence and assess how severe the movement is.
- Monitoring: In some cases, monitoring equipment is installed to track ground and structural movement over a period of time.
- Specialist Reports: Soil tests or a structural engineer’s report may be recommended to pinpoint the underlying cause and the right course of action.
What to Do if You Suspect Subsidence
If you believe your property is affected by subsidence, follow these steps:
- Consult a Chartered Surveyor
A professional surveyor can assess the severity of the subsidence and determine the best course of action. They may recommend monitoring the movement over time or suggest repairs. - Contact Your Insurance Company
Subsidence is usually covered by home insurance, but it’s important to notify your insurer as soon as possible. They may arrange for a structural engineer to inspect your property. - Tree and Shrub Management
If trees or shrubs are the cause, you may need to remove or manage them to prevent further damage. It’s best to consult an arborist or tree surgeon, as removing trees incorrectly can exacerbate the issue. - Repair Water Leaks
Fix any leaking pipes or drains promptly to prevent water from washing away soil around the foundation. - Underpinning
In severe cases, your property may require underpinning, a process that involves strengthening the foundation to prevent further sinking. This is an extensive and often costly repair, but it can provide a long-term solution to subsidence. - Soil Stabilisation
In some cases, injecting a stabilising resin or material into the ground can prevent further movement and restore support beneath the foundation, sometimes as an alternative to full underpinning.
Preventing Subsidence
While you can’t always prevent subsidence, there are some steps you can take to reduce the risk:
- Be Mindful of Tree Planting: Avoid planting trees or large shrubs close to your property. If you already have trees near your home, consult an arborist to manage their growth.
- Regularly Inspect for Leaks: Regular maintenance of pipes and drainage systems can help prevent leaks that wash away supporting soil.
- Choose Suitable Building Sites: If you’re building a new home, make sure the site is suitable and has a stable foundation. Consulting with a geotechnical engineer can help assess the soil type and risks.
How RICS Surveyors Can Help
Dealing with subsidence can feel daunting, but a RICS-accredited surveyor takes the guesswork out of it. Their expertise means an accurate diagnosis and practical, property-specific advice:
- Comprehensive Surveys: A thorough inspection to identify structural issues, including subsidence and its likely cause.
- Professional Reports: A clear report setting out the causes, severity and recommended solutions.
- Peace of Mind: Impartial guidance so you can make informed decisions about repairs, insurance and future maintenance.
Conclusion
Subsidence can be a serious issue, but by understanding its causes, identifying early signs, and taking preventative steps, you can protect your property. Regular property surveys can also help identify potential issues before they escalate, giving you peace of mind and helping you maintain your property’s value.
If you’re concerned about subsidence or want a professional assessment, contact WR Surveying today. Our experienced team of RICS-accredited surveyors can provide a thorough inspection and guidance on how to address any issues.