CROSS Safety Report
Changes in temporary works scheme
This report is over 2 years old
Overview
Changes in the construction programme on site led to the construction of the superstructure of a building, without the liner wall below it being completed.
Key Learning Outcomes
For contractors:
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Quality control and competent supervision on site can help to ensure that the structure is built in accordance with the design. It will also ensure there is adequate consideration of the interfaces between temporary works and permanent works.
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Consider appointing a competent temporary works coordinator (TWC) on site who should be able to identify and address the risk of programme changes
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Any changes made to the construction programme that can impact on the design intent should be reviewed and approved by the design engineer
For structural design engineers:
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This report highlights the potential value of visits by the design team at key construction stages to identify any potential problems
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If you are unable to attend site, consider asking the contractor for site photos of the installation of critical structural elements
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Ask clients and contractors to make you aware of any changes to the brief during construction so that you can consider the impact of the changes on your design
Full Report
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
A multi-storey above ground structure was designed so that the superstructure rested on a basement liner wall, which in turn was dowelled into the secant piled retaining wall. The temporary works designer placed raking props and whaling beams against the secant wall in the temporary case. This prevented completion of the liner wall. A sequence was specified in which all props were removed, and the liner wall completed before construction of the superstructure started.
Due to changes in construction programme, time pressure and lack of clarity about who was responsible for the overall temporary works strategy, the sequence of construction was changed. The construction of the superstructure proceeded without the liner wall being completed.
Due to changes in construction programme, time pressure and lack of clarity about who was responsible for the overall temporary works strategy, the sequence of construction was changed
By the time this was spotted, a significant portion of the superstructure was being supported by a partially complete liner wall, with a greatly reduced number of dowels into the secant wall. Work was immediately stopped on this structure until it was deemed safe and delays were incurred as the superstructure could not be continued until the liner wall was completed.
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Expert Panel Comments
Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.
There have been innumerable failures consequent on change or unauthorised change with unforeseen consequences. Nothing should be changed on site without approval from the design authority and this is a classic case of lack of adequate consideration of the interfaces between temporary works and permanent works.
Was a temporary works coordinator and a temporary works supervisor appointed to help ensure this situation could not occur? The permanent works designers should have provided for at least one safe method of construction, and this should not have been changed without reference back to them.
Changes made to designs on site can have severe adverse consequences and again there are similarities with the Edinburgh schools (Inquiry into the construction of Edinburgh Schools - February 2017). Procedures must be followed, and responsibilities allocated at the start of every project for controlling change.