What are the Signs of Subsidence in a House?

Diagonal cracks, wider at the top than the bottom and larger than 3mm, may be an indication of subsidence. These tend to appear around doors, windows, and in the corners of rooms. Cracks in the external render and brickwork can indicate service movement issues.

Cracks can be a normal part of homeownership, especially in older homes. Settlement cracks can also be evident in new or relatively new buildings, as the home takes time to settle. But, if they are more than a hairline crack and continue to develop, it is worth investigating further.

Foundation shifts can cause wallpaper to ripple or pull apart at joints. If you see this in your home, investigate the cause. Damp can also cause wallpaper to ripple and peel. This would need exploring and rectifying, but it is often less severe than subsidence.

Although wooden doors and window frames can expand and retract as the weather changes, this can be a sign of subsidence. If the frames seem warped, uneven and are “sticking” (not opening and closing properly), you may want to investigate further.

Uneven floors can be a clear sign that something is wrong. Even subtle tilting or gaps between floors, walls and skirting boards can be indications that subsidence is impacting the home.

Certain soil types, such as clay soil can shrink, crack and even shift during hot weather. This creates an unstable ground, pulling the foundations down as it shrinks. Meanwhile, sandy soils can erode over time, leading to subsidence.

Tree roots removing moisture from the soil is one of the most common reasons for subsidence. Large trees, for example, oak, elm and willow, draw moisture from the soil, causing it to shrink. If they're situated close to the property’s foundations, this can cause subsidence. Even if there are no visible roots, this issue could be developing beneath the surface.

Underground leaks in pipes and drains can wash away the soil supporting the foundations of homes. This can then lead to ground instability and collapse. Damage from leaks can happen gradually over time but can rapidly develop during heavy rainfall. It can be exacerbated in the event of a burst water main.

Long periods of dry weather can lead to shrinking soils, which can be a key risk factor in some areas. Extreme wet weather can also be a concern. The ground will expand from the moisture but contract during warmer months. This process of shrinking and swelling can create an unstable ground.

Historic or ongoing mining in the area under and around a property can also lead to subsidence. Pits, mine shafts and excavated land can become unstable. This is why a mining search is an essential part of the conveyancing process.

Underpinning is a construction method used to strengthen the foundation of a property. It adds support to prevent the home from sinking into the ground. The method you opt for will depend on the foundation depths and the severity of the subsidence.

Underpinning can be a disruptive and expensive process. If you live in a semi-detached or terraced home, you may need to consider party wall implications, adding to the cost. This is because the work can have a considerable impact on neighbouring properties.

The most common methods of underpinning include:

• Mass concrete: This method involves a specialist digging holes beneath the existing foundation and filling it with concrete.
• Beam and base: Similar to the mass concrete method, load-bearing beams are laid on top of the concrete.
• Piling: This is usually the most expensive and used for extreme cases. Specialist equipment is used to insert piles to strengthen and support a building’s foundation.

According to RICS, underpinning can cost anywhere between £10,000 and £75,000 or more.

More modern treatments like geo-polymer injections are an alternative to underpinning. These are usually less invasive, quicker and more cost-effective. This technology and method involves strong, expansive resins being injected into the ground. This strengthens the foundations and stabilises buildings.

If Japanese Knotweed is found on your property, ensure it is professionally treated as soon as possible. If you are planning on planting trees or other vegetation, be sure to avoid root issues by planting them a safe distance from any buildings. The Association of British Insurers (ABI) has a guide to tree height, root length and safe distances.

Regularly check for leaks and maintain drainage systems to prevent water damage to soil. Keep drains clear and unblocked and address any issues early on.

Keep an eye on cracks developing in ceilings and walls. If they expand or change, consult a builder or surveyor to assess the situation. It could be a sign that the ground beneath the property is shifting. The best way to be sure of ground instability is to hire a professional to conduct a structural survey.