What Is Subsidence?

Subsidence is the gradual or sudden sinking or settling of the ground level beneath a building or other structure. It occurs when the soil or ground beneath a structure shifts, shrinks, or otherwise loses support, causing the structure to sink or settle unevenly. Subsidence can lead to structural damage and potentially compromise the stability of buildings and infrastructure.

Common causes of subsidence include:

• Ground Shrinkage: In areas with clayey or expansive soils, prolonged periods of dry weather can cause the soil to shrink, leading to subsidence. When the soil regains moisture, it may not return to its original volume, causing the ground to settle.
• Tree Root Activity: Tree roots can absorb moisture from the soil, causing it to dry out and shrink. This can result in subsidence, especially if there are trees located near a building's foundation.
• Underground Mining or Extraction: In regions with mining or quarrying activities, subsidence can occur as underground materials are removed, leaving voids that cause the ground above to sink.
• Water Leaks: Water leaks from broken pipes or drainage issues can saturate the soil beneath a building's foundation, leading to subsidence as the soil's ability to support the structure weakens
• Poor Soil Conditions: Some areas have naturally weak or compressible soils that are prone to subsidence.

Signs of subsidence may include:

• Cracks in walls, especially if they are diagonal or wider at the top.
• Sticking doors and windows due to a distorted frame.
• Uneven or sloping floors.
• Gaps around window or door frames.
• Cracks in external brickwork or stonework.
• The appearance of new or worsening structural damage.

When to call a PIBOB in?

Buildings move, throughout the year and their lifetime buildings have an allowance to settle and move and this does sometimes create cracking.

So, when should you call PIBOB to conduct a Structural Survey?

• Hairline cracks: these can be simply decorated over.
• Cracks with a width of 1mm (you can fit a fingernail in it): these can be decorated over, should they return call PIBOB.
• Cracks larger than 2mm, call PIBOB in.