This claim involved the failure during a storm event of a waterproof fabric structure, located on the rooftop of a school science block. We were engaged by the lawyers representing site shade sail and steel fabrication contractors to investigate the cause of the failure and the history of the project.
On reviewing the files of the project, including the original design drawings submitted by the architect, tender requests and purchase orders issued by the builders, engineering specifications issued by the architect, steel fabrication drawings, tender offers submitted by all parties, various emails between parties, investigations by independent forensic engineers, and site photos of the failed structure, we were able to establish the following salient facts.
- Shortly after submitting the tender response but before receiving a work order the shade sail contractor advised the project architects that a 20 degree fall was required “to prevent ponding”. This advice was rejected by the architect.
- After some discussions between the shade sail contractor, the builder, the project engineers and the architect it was agreed by all that the fall on the tensile fabric structure that was to be erected at the school should be not less than 15 degrees and the tender response was amended to incorporate that new (15 degree) fall with the shade sail contractor accepting the work order on that basis.
- The tender specifications requires that “the Principal will appoint an engineer experienced in the field of tensile structures”;
- At no relevant time was such specialist engineer engaged;
- The contract executed by the company was to supply and install the tensile fabric structure to pre-existing poles erected at the site that were designed, engineered and installed by others. The company was not required to measure the degree of fall on the sail and its directors had always assumed the design had been certified as agreed to by the architect and the builder.
- The company fixed the tensile fabric structure in June 2015 to pre-installed posts and at the time water run off testing showed that water was that ponding on the it;
- The structure collapsed some time in January 2016;
- Measurements of posts heights and set out taken by a forensic engineer after the collapse showed that the degree of fall was somewhere in the region of 9- 11%;
- The cause of the collapse and the exact mode of failure remains unclear with possible causes being:
- Heavy downpour of rain causing ponding because of insufficient fall on the tensile fabric structure design as a result of the architect ignoring our clients stipulation as to the degree of fall required;
- Failure of HD bolts engineering design on or otherwise inadequate work on footings;
- Failure of the builder to issue our clients with revised engineers drawings in relation to the design; or
- Combination of all (a)- (c) above.
It was established beyond reasonable doubt that the failure of the structure was caused by the project architect ignoring professional advice regarding degree of fall required on the waterproof fabric and the site building contractor failing to pass on engineering specifications to mutable sub contractors.