CROSS Safety Report
Unauthorised structural alterations to accommodate drainpipes
This report is over 2 years old
A reporter became aware of cases where main structural steel sections were ‘butchered’ on site to accommodate drainpipes.
The alterations were not approved by the designer and were picked up during a routine inspection by building control.
Key Learning Outcomes
For clients and construction professionals:
Any alterations to structural elements should be approved by the designer prior to works being carried out on site
On building information modelling (BIM) projects it is beneficial for the entire design team, including third-party designers, to have BIM capabilities. This will allow for better collaboration and communication across the project.
Independent supervision on site by the design team or a third-party inspector can reduce the risk of any unauthorised changes from occurring, especially in Risk Category 3 buildings
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On a recent project under construction, a reporter became aware of cases where main structural steel sections were ‘butchered’ to accommodate plastic foul drainage runs. Flanges and webs were compromised significantly.
Clash Detection via BIM
This was, continues the reporter, a BIM project and the clashes should have been picked up with clash detection review. However, much of the detailing was passed down the supply chain to sub- contractors who had no BIM capability.
This meant that the coordination of some key elements was not properly carried out in advance of construction. Furthermore, the building was a Risk Category 3 building which should have had extended supervision in accordance with Table B4 of BS EN 1990.
Quality control on site
This issue once again calls into question quality control on site. It demonstrates a complete lack of understanding by those undertaking the works of the potential consequences of their actions. The defects were picked up by a routine inspection by building control, but it raises further questions on what else has been modified that has been covered up.
It is clear that strict protocols are required before such modifications are carried out and that there must be sign off by the engineer before works are permitted. The lack of control on site which allows such things to prevail is evidence of questionable competency by those managing the construction process.
Expert Panel Comments
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This illustrates several concerns. The fact that inappropriate and potentially catastrophic changes were made to the structure illustrates the need for adequate construction supervision and independent supervision e.g. by the design team. This is discussed further in report 905.
The fact that inappropriate and potentially catastrophic changes were made to the structure illustrates the need for adequate construction supervision and independent supervision
Coordination issues on site
However, one must call into question why the changes were deemed necessary in the first place. Often such unauthorised alterations are made as a consequence of an uncoordinated design, where there has been inadequate interdisciplinary coordination. In this case perhaps between the structural engineer and the building drainage designer.
Clients and project managers need to give the design team the time and tools they need to ensure adequate coordination of the design, to ensure the coordinated design is constructible and without clashes.
Such attention to detail usually results in significant overall cost savings for all parties. BIM should have identified the clashes and the reporter makes the valid point that sub-contractors must be party to the whole system for it to work properly.
This report also shows the valuable role that building control can play, because this type of situation is all too common. It also shows either a blatant disregard for safety, or a lack of knowledge on the part of the contractor – both situations are not acceptable in our industry.
It also ties into report 894 and report 905 of Newsletter 59 (and many other CROSS reports): what has been designed is not necessarily what has been built. A safe construction procedure should recognise that changes are inevitable but must always be controlled and sanctioned by the designer.
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