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902 Unauthorised structural alterations to accommodate drainpipes

Report ID: 902

Report Overview

A reporter became aware of cases where main structural steel sections were ‘butchered’ to accommodate drainpipes.

Report Content

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.

This was, continues the reporter, a BIM project and the clashes should have been picked up, but much of the detailing was passed down the supply chain to sub- contractors who had no BIM capability, meaning 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.

This issue once again calls into question quality control on site and 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.

Comments

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, as discussed further in report 905.

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 complete lack of knowledge on the part of the contractor – both situations are not acceptable in our industry. It also ties into Reports 894 and 905 above (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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View other CROSS reports published in Newsletter 59


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