It became a battle of the engineers on Friday at the labour department's commission of inquiry into the collapse of the Tongaat Mall, outside Durban, last year.
The developer's current engineer claimed there were serious problems with the previous engineer's design plans.
Engineer Rob Young said he received the plans for the mall from structural engineer Andre Ballack.
A portion of the mall, which was under construction, collapsed on November 19, killing two people and injuring another 29.
Ballack was the structural engineer at the time the mall collapsed, and had been appointed by Gralio Precast.
Young, who was the lead design engineer for Durban's King Shaka International Airport and has since been appointed by Gralio Precast to investigate what went wrong, said he and his team had viewed the plans.
"We found material defects that could have led to the collapse," said Young.
Young, and at least three other engineers – Ballack, an engineer from the eThekwini metro municipality, and an engineer from the Engineering Council of SA – are expected to be questioned by the commission in early June.
That, however, will not happen until there has been a site visit by all engineers on March 10 and the controlled removal of debris takes place.
Young explained to the commission that it was necessary to remove the collapsed slab to examine pillars and other items of interest in a bid to determine what caused the collapse.
The labour department's occupational health and safety manager Phumudzo Maphaha, who heads the three-man commission, said that barring anything unexpected, he hoped to present his findings by the end of August.
Earlier this week site foreman Ronnie Pillay told the commission that in the days preceding the collapse one of the concrete slabs sagged by 70 millimetres.
Apart from the sagging slab, he said he had raised concerns over the thickness of the pillars, as well as the lift shaft.
During testimony of the safety consultant hired by Gralio Precast it emerged that there had never been any health and safety audits.
Permission to build the mall was never obtained and the eThekwini municipality had obtained a court order stopping the development.
However, building continued unabated and the mall was scheduled to open in March this year.