Property cracking and subsidence – understanding the causes and what to do

Cracks appearing in a property can be worrying, particularly when subsidence is suspected. However, while subsidence is a well-known cause of cracking, it is important to understand that not all cracking is caused by subsidence. There are many potential causes of cracking, and identifying the underlying cause is essential to determining the appropriate repair.

What is subsidence?

Subsidence is generally described as the downward movement of the ground beneath a building. While this definition is correct, it does not tell the whole story. Cracking can occur for a variety of reasons, including changes in ground conditions, drainage problems, seasonal movement, settlement and the effects of trees on shrinkable clay soils. Some movement can be cyclical, with cracks opening and closing at different times of the year, while other movement can be progressive, with cracks continuing to widen over time. This is why it is important not to assume that cracking automatically means subsidence.

What causes cracking and building movement?

Some of the more common causes of cracking include:

• Trees and vegetation: Tree roots can extract significant amounts of moisture from shrinkable clay soils, potentially causing the ground to shrink and buildings to move.
• Defective drainage: Leaking underground drains can wash away or soften supporting soils, potentially contributing to localised ground movement.
• Seasonal movement: Changes in moisture content and temperature can cause some materials and ground conditions to expand and contract.
• Settlement: Buildings can experience movement as foundations and surrounding ground adjust, particularly following construction or alterations.
• Structural or building defects: Cracking may arise from problems within the building itself rather than movement of the ground.

The appearance, location, pattern and progression of cracks can all provide useful information when determining their likely cause.

What are the signs of subsidence?

Signs of possible building movement can vary considerably. Cracking to masonry or internal stud walls is one of the more obvious indications, but other signs can include:

• New cracks appearing in walls, ceilings or around openings
• Existing cracks becoming wider or reopening after repair
• Doors or windows becoming difficult to open or close
• Distortion around door and window frames
• Changes in floors or other elements of the building
• Other signs of structural movement

It is worth remembering that these symptoms do not necessarily mean a property is suffering from subsidence. They should instead be treated as reasons to investigate further. If a crack is new, worsening or has reopened after being repaired, it is sensible to seek professional advice.

How can a structural engineer from Structural Engineers Reports help?

Our structural engineers have extensive experience in the assessment of cracking and building movement. Through a detailed inspection and assessment, we can help determine:

• The most likely cause of the cracking
• Whether the movement appears to be progressive or cyclical
• The severity and significance of the damage
• Whether further investigation is required
• The most appropriate next steps and repair strategy

We follow relevant guidance from organisations including the Institution of Structural Engineers (IStructE) and Construction Industry Research and Information Association (CIRIA) when assessing building damage and considering appropriate remedial measures. The aim is not simply to identify and repair the visible crack, but to understand why the movement has occurred in the first place.

If you are concerned about cracking or possible subsidence, our structural engineers can assess the damage, investigate the likely cause and advise you on the most appropriate course of action.