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Structural Survey of Warehouse with Severe Cracking

Our client’s warehouse walls had large cracks that were getting worse. We carried out a specific structural inspection to assess the damage and the risk of harm to users of the building, and to recommend remedial works.

Brief: To inspect significant cracks that were worsening in the walls of an industrial warehouse building.

Property: Steel portal framed industrial warehouse near Milton Keynes.

Instructed by: Health and Safety Officer.

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Project Specification

  • Significant damage and cracking had been observed to the external brickwork walls, along with significant settlement and cracking of the external concrete slab.
  • The client advised that the cracking had got noticeably worse over the past 4 months.
  • Given that a change in use of the warehouse was planned, the client wanted to understand the extent of the damage and the risk to users. 
    • They also wanted to know what could be done to fix the problem.
  • We carried out a specific structural inspection of the warehouse, to answer the client’s concerns.
Cracking inspection of industrial warehouse

Our Findings

Inspection

  • We found moderate–to–severe cracking in several areas of the external wall.
    • The width of the cracks was up to 30mm at the top end of the cracking.
  • Movement of surrounding brickwork had led to distortion and buckling of window frames.
  • We also observed opening up of a vertical movement joint, which now had a gap of over 20mm.
    • The wall ties spanning the joint had bent and the brickwork either side of the joint was no longer level.
  • Significant cracking was also evident in the external concrete slab.
    • This was caused by settlement of the ground below one corner of the building.
  • Leaning and dropping of a low external wall was a further sign that ground movement had taken place.
  • Our structural engineer noted that rainwater downpipes were positioned close to the area of the building where ground movement had occurred. These were collecting water at the base, suggesting that they may not be draining sufficiently.
  • We also found a semi-mature tree approximately 4 metres from the damaged area of the building.
  • Inside the property, the cracking observed in the external brickwork was reflected in the internal blockwork.
  • We also observed a very large horizontal crack at the junction between the ground floor slab and the rear external wall.

Conclusion and recommendations

  • The movement and damage was isolated to one corner of the building; this appeared to be due to ground movement.
  • Fortunately, there was no evidence of movement of the main steel portal frame structure.
    • The frame structure was believed to be supported on deep pile foundations.
    • The main frame structure was concluded to be robust and stable.
  • Instead, the movement and damage was restricted to external cavity walls, which were supported by the concrete slab, rather than deep foundations.
  • The slab had been affected by downwards ground movement in one corner of the plot, resulting in subsidence.
    • The subsidence could have been caused by:
      • inadequate water drainage, leading to softening and eroding of the concrete slabs
      • nearby trees exacerbating volume change of the clay subsoil
      • loose or poor ground, which is particularly susceptible to movement.
  • In accordance with BRE Digest 251:
    • cracks up to 5mm in width can be re-pointed to ensure weather-tightness
    • cracks up to 15mm in width can be patched by a builder, including repointing of external brickwork and a small amount of brickwork replaced and re-built
    • where brickwork has fractured and distorted considerably, the damaged areas will require propping, breaking out and re-building in order to re-bond all the masonry back together.
  • We recommended that the client contact their Buildings Insurers and start a claim under the subsidence section. This would cover further intrusive inspections to confirm the cause of the movement, such as a CCTV camera survey of the drainage, trial hole excavations and laboratory analysis of soil samples.
    • It would also cover the cost of repairs and any remedial works, such as underpinning, to prevent further movement.

Read more about our structural inspections here, and more about our structural engineering services here.

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