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CROSS Safety Report

Shop/domestic building collapse

Report ID: 123 Published: 1 January 2009 Region: CROSS-UK

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Overview

A two storey corner (end of terrace) property fronting a very busy, narrow major route collapsed during the construction of a new basement.

Key Learning Outcomes

For homeowners:

  • Competent contractors should be appointed to undertake and deliver the project

  • Be aware that planning permission and building regulations approval are an essential pre-requisite to carrying out alterations

For builders:

  • It is important to recognise and know the boundaries of your expertise and work within the limits of your competence
  • Be aware that Health and Safety legislation places duties on individuals as well as companies to ensure that they do not put people at risk of harm

Full Report

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The building was a two storey corner (end of terrace) property fronting a very busy, narrow major route in an area which is normally busy with pedestrians and traffic (Figure 1). On the ground floor there was a shop and there was residential accommodation above. Work had been in progress, without planning or building regulations approval, for about a month to create a basement and loft conversion. A Building Control Surveyor visited the property and advised the builder to stop work until the permissions had been resolved. However, work continued.

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Figure 1: property before the collapse

Internal cross walls had been removed and chimney breasts had been removed from the party wall. It appeared that the internal area was gutted, and the floors were supported on new steel beams spanning parallel to the front from party wall to flank wall. The robustness of the structure had been seriously compromised as there was virtually no lateral stability system. The external walls had been underpinned, rather poorly, onto largely non-cohesive soil, and at the time of failure a mini digger was excavating for the basement. It is suspected that the digger undermined the toe of the underpinning.

As a consequence, the underpinning began to kick inwards and the pavement adjacent to the flank wall started to collapse. Police and Fire Brigade services were summoned and immediately called in building control. The building control engineer who was summoned to the scene was concerned about stability but was unable to establish the extent of the work without entering the building. They decided that it was not safe to do so. Within minutes the building collapsed into the basement and scaffolding was thrown across the streets (Figure 2). There were no injuries.

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Figure 2: property after collapse

Expert Panel Comments

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The lesson to be learned is that this alteration work showed a total lack of understanding of the first principles of building stability and of the way that stability can be compromised by alterations and inadequate phasing of the work. Planning permission and building regulations approval are an essential pre-requisite to carrying out alterations. The involvement of a structural engineer or building surveyor would have prevented this needless destruction. The skill and ability of the building control engineer called to the scene is to be admired.

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