What happened
On Saturday, 10 August 2019, part of the grandstand roof at the AZ stadium in Alkmaar collapsed. The structure fell onto a seating area with capacity for approximately 1,400 spectators. Fortunately, no audience was present at the time of the incident, resulting in zero fatalities. The stadium had been in use for thirteen years when the failure occurred.
The investigation
The Dutch Safety Board (OVV) examined how the structural safety of buildings is guaranteed during their operational phase. The inquiry focused on the specific causes of the roof failure and broader systemic issues regarding building maintenance in the Netherlands. Investigators reviewed the design specifications, construction records, and inspection history of the stadium.
Findings
The collapse was triggered by the failure of welded joints in four roof trusses. The investigation identified several critical shortcomings:
- Design errors: The complex profile transition in the first failed joint was not correctly accounted for, and wind loads were miscalculated.
- Construction defects: Finished welds were thinner than specified, and welding errors were present.
- Lack of monitoring: A crack formed shortly after construction but went undetected. Over time, this crack grew, weakening the joints. Severe rust formation was also observed.
None of the parties involved in the construction recognized these shortcomings initially. During the stadium's thirteen years of use, there were no further examinations of the technical condition of the joints. Consequently, the owner lacked a clear understanding of the declining structural safety. The roof eventually collapsed under a load far lower than its designed capacity.
The OVV noted that this incident is not isolated. An inventory revealed at least sixty serious structural problems in Dutch buildings over the past twenty years. Current legislation places legal responsibility for building safety on the owner but does not specify how to achieve it, nor does it mandate periodic assessments of structural safety. There is also no systematic national approach to recording and analyzing such occurrences to learn from them.
Safety action
The Dutch Safety Board issued recommendations primarily to the Minister of the Interior and Kingdom Relations:
- Introduce a statutory requirement for owners of consequence class 3 buildings (such as stadiums) to carry out periodic structural safety investigations by independent certified experts.
- Ensure municipal authorities monitor compliance with these obligations.
- Require that complete building files, including inspection reports, be passed on during any change of ownership.
Additionally, the Board recommended that industry bodies integrate these lessons into their action plans for improving construction sector safety and that the Royal Netherlands Football Association (KNVB) encourage license holders to comply with structural safety protocols.