Engineering and consultancy firm Royal HaskoningDHV has completed its investigation into the partial roof collapse at AZ Alkmaar’s AFAS Stadion and has found that a failed top rail girder connection was to blame.

AZ Alkmaar hired Royal HaskoningDHV in August after part of the roof collapsed at the Dutch Eredivisie football club’s stadium. The incident occurred amid strong winds on a non-match day and nobody was injured following the collapse.

Following the incident, solar energy company Sunprojects denied reports that the installation of its products could have been to blame for the collapse. An interim investigation from Royal HaskoningDHV then found that the incident was caused by a downward wind load on the roof and full details of the firm’s findings have now been revealed.

The final report found that the main cause of the collapse was that the welds in the stand were too thin, with design errors in the joints contributing to the collapse. The downward wind load led to the roof of the collapse, with the structure having been weakened by a storm shortly after the stadium was opened back in 2006.

Royal HaskoningDHV found that the solar panels did not have an impact on the collapse of the roof.

AZ’s general director Robert Eenhoorn said: “It is great that Royal HaskoningDHV has carefully investigated the cause of the partial collapse of the roof.

“This has created clarity about the cause. We are still incredibly happy that the stadium was empty when the collapse happened, leaving no injuries. Now we can take a new step. In consultation with all relevant parties, we now focus on the future and we will start working hard as soon as we have left the coronavirus crisis behind us.

“Health is of course the most important priority at the moment, but we will keep you informed of the developments surrounding the new roof. Of course, the safety of our supporters and employees has the highest priority.”

In January, AZ revealed that AFAS Stadion would remain without a full roof for the rest of the 2019-20 season as the club detailed expansion plans for the stadium. AZ returned to the stadium on December 15 after playing its ‘home’ matches at ADO Den Haag’s Cars Jeans Stadion following the roof collapse.

The club had hoped to install a new roof in the summer but the uncertainty caused by the COVID-19 crisis may lead to this being pushed back. Eenhoorn also hopes to expand the stadium by 2,500 to 5,000 seats.

AFAS Stadion has a current capacity of 17,000.

Image: AZ Alkmaar