Y2018-01 Collapse of the roof of an activity park in Tornio on 15 March 2018

On Thursday evening, 15 March 2018, approximately 130 square metres of the roof of an activity park collapsed in Tornio. At the time of the incident, some 120 children and adults were present, spending time on various climbing frames and equipment. In the accident, roof structures and snow on the roof fell down. Two collapsed roof supporting beams were left hanging. At the time of the collapse, seven children were playing in a simulator. Approximately two cubic metres of snow fell on the protective net above the simulator. The net was able to support the snow, allowing exit from the activity site in question. No-one was injured in the accident.

The fallen glued laminated timber beams served as secondary supporting beams for the roof. They were obliquely connected to the primary beam at the same level, without support from the floor. The skew joint of the beams was implemented using joist hangers welded from steel plates, extending over the primary beam. The roof collapsed, because a critical welding joint failed in two joist hangers. All joints in the joist hangers were only welded on one side, and the welding did not extend throughout the plate. The designs of the joist hangers were not available and the welder is not known. At the time when the joist hangers were manufactured, the qualification requirements of designers were mainly based on a degree. Quality assurance of the welding work was based on in-house control.

The building was an old industrial and warehouse building, for which an alteration of the intended use had been applied. Due to the alteration and legislation, a condition survey of the load-bearing structures, as required by building control, had been performed in the building. Attention was not paid to the joist hangers during the inspection. The joist hangers were not inspected because: 1) the lack of designs was not recognided as a risk, 2) no previous breakages of similar nature were known, and 3) visual inspection of the joints was impossible.

The Safety Investigation Authority, Finland repeats the recommendation issued in 2004 and reiterated 2011 and 2012, according to which

- A database should be developed to the building trade under the direction of the Ministry for the Environment. In this database information should be compiled on as many incidents and hazardous situations in the building trade as possible. Everybody should have access to the database in question and the information should be summarized at appropriate intervals.

The Safety Investigation Authority, Finland repeats the recommendation issued in 2007, according to which

- The Ministry for the Environment should take action to pool the building inspection of separate municipalities into larger units in such a way that each regional building inspection would have enough expertise to supervise and monitor various kinds of buildings and structures.

Y2018-01 Tornio report (in Finnish) (pdf, 1.98 Mt)