An interim investigation has found that the partial roof collapse at AZ Alkmaar’s AFAS Stadion last month was caused by strong winds.

The Dutch Eredivisie football club hired engineering and consultancy firm Royal HaskoningDHV to investigate after the centre of AFAS Stadion’s Molenaar Stand caved in on itself on August 10. The stadium was not in use at the time and nobody was injured.

Royal HaskoningDHV has now revealed a number of findings from the incident, which it says was caused by a downward wind load on the roof.

It has also been concluded that the connections of the roof trusses are not well designed and the welds are not strong enough and probably too thin. The roof had also been weakened by earlier storms.

AZ said further investigation is required to reach a final conclusion on the incident. Research is likely to be completed in the first quarter of 2020.

Royal HaskoningDHV also noted that the solar panels installed at the stadium had a limited impact on the incident. Solar energy company Sunprojects had already moved to deny reports that the installation of its products could have been responsible for the partial roof collapse.

AZ managing director Robert Eenhoorn said: “We welcome the report of Royal HaskoningDHV and are relieved that there is clarity about the cause of the partial collapse of the roof.

“But we are even more relieved that no people were injured when the roof partly collapsed. For AZ, the safety and trust of our supporters and employees are paramount. Partly for this reason, it was decided to remove three-quarters of the existing roof as quickly as possible in order to create a safe situation as quickly as possible. We did this naturally in consultation with all relevant parties. After this we will work on the design of the new roof.”

Eenhoorn added: “In addition, we are taking the opportunity to tackle a number of issues relating to comfort and possible expansion of the stadium at the same time, so that we can enter the future with confidence. Everything is first focused on being able to play football safely in our own stadium as quickly as possible.”

Image: AZ Alkmaar