Signs of Subsidence in Garden

Subsidence can wreak havoc on a property, and gardens are often the first places where signs become visible.

Homeowners should remain vigilant for telltale indicators that the ground beneath their feet is shifting.

Common signs of subsidence in gardens include uneven lawn surfaces, cracks in paving or patios, and leaning walls or fences. These seemingly minor issues can point to more serious structural problems developing beneath the surface.

Gardeners might notice plants wilting unexpectedly or trees suddenly leaning at odd angles. Such changes in vegetation can signal alterations in soil composition or moisture levels, potentially linked to subsidence.

Recognising these early warning signs allows homeowners to take swift action, potentially preventing more extensive damage to their property.

Regular garden inspections, particularly after periods of heavy rain or drought, can help catch subsidence-related issues before they escalate.

Addressing these concerns promptly can save both time and money in the long run.

Understanding Subsidence

Subsidence poses significant risks to property structures. It involves ground movement that can destabilise foundations and cause damage to buildings.

Recognising the causes and differentiating subsidence from other forms of ground movement is crucial for homeowners and property managers.

What Is Subsidence?

Subsidence refers to the downward movement of ground supporting a building. It occurs when the soil beneath a structure becomes unstable or loses volume, causing the foundation to sink.

This movement can lead to cracks in walls, floors, and ceilings.

Subsidence often affects older properties built on clay soils, but it can happen to any building. The severity varies, ranging from minor settlement to major structural issues requiring underpinning.

Key indicators include:

• Diagonal cracks wider at the top than bottom
• Doors and windows sticking
• Rippling wallpaper not caused by damp

Causes of Subsidence

Several factors can trigger subsidence:

1. Clay soil shrinkage: Clay expands when wet and shrinks in dry conditions.
2. Tree roots: They extract moisture from the soil, causing it to shrink.
3. Leaking drains: Water can wash away or soften soil beneath foundations.
4. Mining: Old mine workings can collapse, causing ground instability.
5. Drought: Extended dry periods lead to soil moisture loss.

Poor groundworks and inadequate foundations can exacerbate these issues. Environmental factors like prolonged rainfall or drought cycles also play a role in subsidence risk.

Distinguishing Subsidence from Settlement

While subsidence and settlement both involve ground movement, they differ in nature and impact:

Settlement:

• Natural process as buildings ‘bed in’
• Usually occurs within first few years after construction
• Movement is generally uniform across the structure

Subsidence:

• Can happen at any time
• Often affects only part of the building
• Movement is typically more severe and ongoing

Historic movement in older properties may have stabilised and not require intervention. However, new or progressive movement warrants investigation by a structural engineer.

Identifying the type of ground movement is crucial for determining appropriate remedial actions and potential insurance claims.

Identifying Signs of Subsidence

Recognising subsidence early can prevent extensive damage to your property.

Key indicators include structural changes, vegetation issues, and water-related problems that may affect your home’s stability.

External Indicators

Cracks in exterior walls are a common sign of subsidence. These cracks often appear diagonally and are wider at the top than the bottom. They typically measure more than 3mm in width and may be visible near windows or doors.

Brickwork might also show signs of separation or bulging.

Look for doors and windows that stick or don’t close properly. This can indicate a shift in the building’s structure.

Exterior paint may crack or flake off more easily in affected areas.

Check for leaning or tilting of external structures like garden walls or fences. Uneven paving or driveways can also suggest ground movement beneath the property.

Internal Warning Signs

Inside the home, wallpaper may crease or tear, particularly where walls meet ceilings.

Cracks in plasterwork, especially around doorframes and windows, can signify subsidence. These cracks might be more noticeable than typical settling cracks.

Observe floors for signs of sinking or unevenness. Gaps may appear between skirting boards and floors. Interior doors might become difficult to open or close.

Look out for new or worsening cracks in ceilings, particularly if they appear to be growing. Lintels above doors and windows may show signs of failure or sagging.

Understanding the Role of Vegetation

Trees and shrubs near the property can contribute to subsidence by drawing moisture from the soil. This is particularly problematic in clay soils, which shrink as they dry out.

Large trees within 10-20 metres of your home pose the highest risk. Species like oak, willow, and elm have extensive root systems that can affect soil stability.

Regular pruning can help manage this risk. However, sudden removal of large trees can cause soil to swell as moisture levels increase, potentially leading to heave.

Monitor any changes in nearby vegetation, including new growth or the removal of established plants. These changes can affect soil moisture content and stability.

Impact of Water and Drainage Issues

Leaking drains and pipes can wash away soil beneath foundations, leading to subsidence. Signs of water damage or damp patches on walls may indicate underground leaks.

Check for pooling water around the property after rainfall. This could suggest poor drainage, which may contribute to soil instability.

Burst pipes or long-term leaks can erode soil and create voids under the property. Be alert to unexplained increases in water bills, which might indicate hidden leaks.

During dry spells, soil can shrink and crack, potentially affecting foundations. Consistent watering of gardens during drought can help maintain soil moisture levels.

Professional Assessment and Diagnosis

Accurate identification of subsidence requires expert evaluation. Structural engineers play a crucial role in assessing potential issues and recommending appropriate solutions.

Thorough surveys and precise crack analysis are essential for distinguishing between superficial damage and serious structural problems.

Role of a Structural Engineer

A qualified structural engineer is vital for diagnosing subsidence. These professionals possess specialised knowledge to assess a property’s structural integrity.

They examine foundations, soil conditions, and building materials to determine the root cause of subsidence.

Structural engineers use advanced tools and techniques to measure movement and evaluate the extent of damage.

Their expertise allows them to differentiate between subsidence and other issues like normal settlement or thermal expansion.

Based on their findings, they provide detailed reports and recommend suitable remediation strategies.

Conducting Structural Surveys

Structural surveys are comprehensive examinations of a property’s condition. A chartered surveyor or structural engineer carries out these inspections to identify signs of subsidence and assess overall structural health.

The survey process typically involves:

• Visual inspection of external and internal walls
• Measurement of cracks and monitoring their progression
• Assessment of door and window frames for misalignment
• Examination of floors for unevenness or sloping
• Inspection of the roof structure and chimney stacks
• Evaluation of drainage systems and soil conditions

Surveyors may use specialised equipment such as crack monitors, laser levels, and moisture meters to gather precise data. The resulting report provides a thorough analysis of the property’s condition and highlights any areas of concern.

Distinguishing Between Cosmetic and Structural Cracks

Identifying the nature of cracks is crucial for determining the severity of subsidence. Cosmetic cracks are typically superficial and do not indicate structural problems, while structural cracks can signify serious issues.

Key differences include:

Cosmetic Cracks	Structural Cracks
Usually less than 5mm wide	Often wider than 5mm
Appear in plaster or render	Extend through brickwork or masonry
Horizontal or vertical	Often diagonal or stepped
Do not widen over time	May progressively widen

Hairline cracks are common in new buildings due to initial settlement and are generally harmless. However, cracks that suddenly appear or rapidly widen may indicate active subsidence.

A structural engineer can accurately assess crack patterns, depths, and locations to determine their significance and recommend appropriate action.

Treating and Preventing Subsidence

Addressing subsidence requires a multi-faceted approach involving structural repairs, soil management, and landscape modifications. These methods aim to stabilise the ground and prevent further sinking or movement of buildings and garden structures.

Underpinning Solutions

Underpinning is a crucial technique for stabilising structures affected by subsidence. It involves extending the foundations to more stable soil layers. Common methods include mass concrete underpinning and mini-piled underpinning.

Mass concrete underpinning suits shallow foundations and involves excavating sections beneath the existing foundation and filling them with concrete.

Mini-piled underpinning is ideal for deeper foundations or difficult soil conditions. It uses small-diameter piles driven into the ground to transfer the load to more stable soil layers.

Both techniques require careful planning and execution by experienced professionals to ensure the structural integrity of the building. The choice between methods depends on soil conditions, building type, and extent of subsidence.

Remediating Soil and Drainage

Soil and drainage issues often contribute to subsidence, especially in clay soils prone to shrinkage. Addressing these problems can prevent further sinking and stabilise affected areas.

Key remediation steps include:

• Repairing leaking drains and pipes to prevent soil erosion
• Improving surface drainage to direct water away from buildings
• Installing root barriers to protect foundations from tree roots
• Treating expansive clay soils with lime or cement to reduce moisture sensitivity

In cases of heave, where the ground swells upwards, removing trees or managing groundwater levels may be necessary. Professional groundworks may be required to implement these solutions effectively and safely.

Gardening and Landscaping Adjustments

Proper garden management plays a vital role in preventing subsidence. Trees and shrubs can significantly impact soil moisture levels, leading to soil shrinkage or expansion.

Important gardening practices include:

• Planting trees and large shrubs at a safe distance from buildings (typically 1.5 times the mature height)
• Regular pruning to control tree size and water uptake
• Choosing plants suitable for local soil conditions
• Maintaining consistent soil moisture levels through proper watering techniques

In existing gardens, removing or crown reducing large trees near structures may be necessary. However, sudden removal can cause soil heave, so gradual reduction is often preferable.

Consulting an arboriculturist can help determine the best approach for managing vegetation to prevent subsidence.

Insurance and Legal Considerations

Subsidence can significantly impact property values and insurance coverage. Homeowners need to be aware of their insurance policies and legal obligations when dealing with subsidence issues.

Understanding Home Insurance Policies

Most standard home insurance policies cover subsidence damage, but often with a higher excess. Typically, this excess ranges from £1,000 to £2,500.

It’s crucial to review policy details carefully, as some insurers may exclude certain types of subsidence-related damage.

Insurers generally cover repairs for the first instance of subsidence. However, subsequent claims might be more challenging. Some policies offer a ‘trace and access’ cover, which pays for locating the source of the problem.

When making a claim, insurers often require a thorough investigation to determine the cause and extent of subsidence. This may involve soil tests and structural surveys.

Selling a Property Affected by Subsidence

Sellers must disclose any history of subsidence when putting a property on the market. Failure to do so can lead to legal complications and potential lawsuits.

Properties with a history of subsidence may see a reduction in market value. Buyers often struggle to secure mortgages or insurance for such properties, which can make sales challenging.

To mitigate these issues, sellers should:

• Provide detailed records of all repairs and underpinning work
• Obtain a structural survey to demonstrate the property’s current stability
• Consider offering indemnity insurance to protect buyers against future subsidence claims

Estate agents should be informed of any subsidence history to ensure accurate property listings and avoid potential legal disputes.