Borough wide – Cantilever Balconies Investigation & Appraisal

  • Client: Enfield Council Housing
  • Services: Risk Management, Investigation / Testing of Building and Appraisal of Structural Form
Acting in the role of the Council’s Structural Engineer, we brought this issue to the attention of the Housing Client and subsequently received instructions to investigate the potential risk to buildings throughout the borough with similar balcony construction – mainly affecting communal balconies of cantilever construction.
Contract Value:
£25k
Dates:
2013-2015
Contracts:
SLA arrangement
In 2012, a cantilever balcony collapsed from across the full elevation of a 1960’s, 3-storey block of flats in Blackpool. The reinforcement was found to be incorrectly positioned in the bottom of the concrete slab, but somehow had managed to support the balcony for over 50 years, until the effects of corrosion finally took their toll.

Acting in the role of the Council’s Structural Engineer, we brought this issue to the attention of the Housing Client and subsequently received instructions to investigate the potential risk to buildings throughout the borough with similar balcony construction – mainly affecting communal balconies of cantilever construction.

Our initial approach involved a preliminary survey of all medium rise buildings throughout the borough, which helped us to identify the different types of balconies present. Those of similar suspect construction were then subject of a more detailed investigation supplemented by undertaking elements of non-destructive testing. This including checks on the concrete cover to reinforcement to establish the position of the slab reinforcement. Close inspection of the waterproofing detail and its condition at the interface of the external wall and balcony slab and engineering judgement were used to determine the likelihood of reinforcement corrosion and hence whether any immediate risk mitigation measures were required in the interest of safety.

Services

  • 01
    Investigation / Testing of Building
  • 02
    Appraisal of Structural Form
  • 03
    Risk Management

Based on our initial findings, follow-on invasive investigation including representative sampling and testing were recommended to the client in the case of some of the balcony types. This testing was necessary to confirm the actual arrangement and condition of the slab reinforcement, the strength and condition of the concrete and the slab thickness, to allow our assessment of the current and future structural integrity of the balcony slab.

Delivery

  • Pro-active approach by identifying a potential safety hazard to the client
  • Survey and investigation of over 500No. blocks. Development of a bespoke Access database to help manage the volumes of survey data.
  • Structural appraisal and risk assessment
  • Recommendations for risk mitigation measures, including temporary propping, holding repairs, strengthening or balcony replacement

The HSE have recently written to all local authorities in England to warn them of this potential problem, which could affect other balconies of similar construction,

Steve Davis Project Director for Capital

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