How to identify and fix subsidence in your home

This guide outlines the telltale signs of subsidence, and the steps to fix subsidence in your home.

Subsidence in a home is when the ground beneath a building sinks or shifts, causing the foundation to move. This can lead to cracks in plaster and other walls, floors, or ceilings, doors and windows not fitting properly, or uneven floors. It happens because the soil beneath the foundation loses its strength or volume, often due to changes in moisture levels, like from droughts, tree roots, or leaking pipes. Subsidence can lead to structural damage and may need significant repairs to stabilize the house.

Subsidence can occur anywhere, but some areas experience it more than others. Data shows that the states with the most severe subsidence problems in homes are those with expansive clay soils or areas prone to underground water withdrawal.

In the UK, subsidence is a common issue in certain areas, typically where soil types, environmental conditions, or infrastructure contribute to ground movement. The areas most prone to subsidence problems with homes include:

• London and the Southeast – These regions are particularly vulnerable due to a large amount of clay soil, which expands and contracts with changes in moisture levels. This makes properties here more prone to subsidence, especially during dry periods.
• East Anglia – Known for sandy and clay soils, this region also experiences significant subsidence problems, especially in periods of drought when the soil shrinks.
• The Midlands – Parts of the Midlands, particularly around Birmingham, experience subsidence due to a mix of clay soils and historical mining activity, which can cause ground movement.
• North West England – Cities like Manchester and Liverpool are also affected, particularly due to mining in certain areas and older infrastructure that may not be as resistant to ground movement.
• South Wales – Mining areas in Wales, particularly near Cardiff and Swansea, are also prone to subsidence, with ground instability often linked to former coal mining operations.

In the USA, The most affected states include:

• Texas – Especially in cities like Houston and Dallas-Fort Worth, due to clay soils that shrink and swell.
• California – Certain areas experience subsidence from groundwater extraction and clay soil shrinkage, as well as seismic activity.
• Florida – Sinkholes from limestone dissolution are a major issue, particularly in central Florida.
• Louisiana – Subsidence occurs due to groundwater withdrawal and natural soil compaction, especially in coastal areas.
• Arizona – Phoenix and Tucson face subsidence caused by extensive groundwater pumping.
• Nevada – Las Vegas has similar issues due to groundwater withdrawal.

These states see frequent problems with foundation damage, cracks, and structural shifts in homes. And where those signs appear, they can often be a clue that there are bigger problems in the neighbourhood.

There are extreme risks posed by subsidence, particularly in areas with vulnerable geological formations. So it’s wise to keep an eye out for the early signs and then quickly work on evaluating and fixing subsidence!

What are the signs of subsidence?

Here are some common signs that your home might be suffering from subsidence:

Cracks in walls

Look for cracks that are wider than 3mm (about the width of a pencil), especially if they appear suddenly, grow over time, or are diagonal and wider at the top than the bottom.

Doors and windows sticking

If doors or windows suddenly start jamming or not closing properly, it could mean that the frame is warping due to foundation movement.

Uneven floors

A noticeable slope in the floor can indicate subsidence, especially if it wasn’t there before.

Gaps around windows and doors

Gaps may appear between the walls and the frames of windows or doors as the structure shifts.

Cracks where extensions meet

If you have an extension, cracks where the extension joins the main house can be a sign of the two parts moving differently due to subsidence.

Gaps between walls and floors

You might notice gaps between your walls and floors or between walls and ceilings due to the shifting foundation.

Rippling wallpaper

If wallpaper starts to ripple or tear without any sign of dampness, it could be caused by subsidence. You will need to remove the wallpaper to check.

External signs

Outside the house, you might see cracks in brickwork or the foundation, and sometimes the building might look like it’s tilting slightly.

Leaning chimneys

A chimney that appears to be leaning away from the house is another potential sign of subsidence.

If you notice any of these signs, it’s important to contact a professional for an assessment. If you just let it go on, it can lead to far worse — and cnsiderable more expensive — repair bills down the track. Why? Read on…

What happens if you don’t fix subsidence?

If subsidence is not fixed in a home, it can lead to serious dangers and long-term issues, including:

• Structural instability: The most significant risk is that subsidence can compromise the structural integrity of the home. The foundation can weaken to the point where parts of the building may collapse.
• Worsening cracks: Cracks in walls, ceilings, and floors will likely continue to grow, leading to potential collapse of walls, chimneys, or other parts of the house.
• Water damage: Cracks can allow water to seep into the building, causing dampness, mold, or rot. This can further weaken the structure and create health risks from mold spores.
• Safety hazards: Doors and windows that become stuck due to subsidence can be dangerous, especially in emergencies when quick exits are needed.
• Decreased property value: Homes with unresolved subsidence problems can lose value significantly. It may also become difficult to sell the property, and some insurance companies may refuse to offer coverage until the issue is resolved.
• Increased repair costs: The longer subsidence is left unaddressed, the more extensive and expensive the repairs may become. Delaying can mean more severe damage and the need for more invasive stabilization methods.

Fixing subsidence early helps prevent these risks and avoids the need for costly structural repairs later.

What are the processes?

Fixing subsidence in a home typically involves stabilizing the foundation and addressing any underlying issues causing the ground to sink. Professionals use various techniques depending on the severity and cause of the subsidence. Here’s an overview of the common processes:

Underpinning

Underpinning is the most common method for severe subsidence where the foundation needs extra support. It involves trengthening the foundation by extending it deeper into more stable ground.

1. The soil beneath the foundation is excavated in sections.
2. Concrete or steel supports are inserted to support the foundation.
3. This deepens the foundation, redistributing the weight of the building to more stable soil layers.

Resin Injection (Soil Stabilization)

This method is faster and less disruptive, typically used for minor subsidence where the soil has lost volume but not its bearing capacity. It involves using expanding resin to fill voids and stabilize the ground beneath the home.

1. Small holes are drilled into the foundation or surrounding soil.
2. A liquid resin is injected into the holes, which expands and solidifies, strengthening the soil.

Piling

Piling is often used for more severe subsidence when the top layers of soil are too weak or unstable to support the building. It involves inserting deep concrete or steel piles into the ground to support the foundation.

1. Holes are drilled deep into the ground until they reach stable soil or bedrock.
2. Steel or concrete piles are inserted into these holes to carry the building’s weight.

Root Removal and Tree Management

This is used when subsidence is caused by nearby trees or vegetation. It requires removing or managing trees and vegetation that are contributing to the subsidence.

1. If tree roots are drawing too much moisture from the soil (causing shrinkage), they may be pruned, or the tree may be removed.
2. In some cases, a root barrier may be installed to prevent roots from affecting the foundation.

Fixing Leaking Pipes

This method is used when subsidence is caused by water leaking from broken or rburst pipes. It requires Repairing or replacing damaged pipes that are causing soil erosion beneath the foundation.

1. Plumbing is inspected for leaks.
2. Any damaged pipes are repaired or replaced to stop the water from washing away soil beneath the foundation.

Drainage Improvements

Drainage improvements are needed if poor drainage is causing soil to become waterlogged and unstable. It involves improving the drainage system to prevent water accumulation near the foundation.

1. Drains may be added or redirected away from the building.
2. Sometimes, a ‘French drain ‘or sump pump system is installed to keep water from pooling around the foundation.

After the structural problem is fixed…

Crack Repair and Cosmetic Work

This is the final stage after stabilizing the subsidence problem. Once the foundation is stabilized, professionals will repair any cracks in walls or ceilings.
Cracks are filled and repointed, often with flexible materials to accommodate any further minor movements. Damaged plaster or brickwork is replaced, and cosmetic repairs are completed.

Monitoring and Aftercare

Professionals may install monitoring devices to check if the foundation remains stable after the repairs. Monitoring the foundation for further movement after repairs is crucial to be alerted to future potential problems.

Further actions can be taken if any signs of continued movement are detected.
The method chosen depends on the cause and severity of the subsidence. A professional will first assess the home to determine the most appropriate solution.