B2/2005Y Collapse of the Inner Ceiling Structures of a Local Supermarket in Sysmä on 27 April, 2005

On Wednesday 27.4.2005 at 9.29, half of Sysmä S-Market’s inner ceiling structure collapsed. The collapse took approximately 10 seconds. During the accident there were 25 people in the building, nine of whom were in the damaged 400-square-metre area. Nobody was injured in the accident.

The inner ceiling had to be renewed. Lighting fixtures, installation bars and cables, cooling equipment pipes, air ducts, and damaged fixtures underneath were also renewed. The part of the inner ceiling that did not collapse was reinforced. Total costs caused by the accident were approximately 270 000 euros. The local co-operative company had the inner ceilings of all their shops and restaurants inspected and the necessary repairs were made.

The cause of this accident was the nail joints that joined the inner ceiling battens to the roof trusses. These joints were not strong enough. The joints had mostly two nails nailed with a compressed air nail gun. The load capacity of the nails was not adequate for the weight of the inner ceiling and the masses attached to it.

The nail joint details had not been designed in 1997 when the building was built. The loads were not evaluated and the load capacity of this type of joint was not ensured. The drawings did not indicate how the joint should be made. For this reason, the contractor used a method that was familiar and used before.

The investigation board does not give safety recommendations, because the investigation report as such gives information on how to avoid similar accidents in the future. The technical causes of this accident are clear, and several improvements have been made since the building was built in 1997. Recommendations for improving ceiling structure safety have been given in previous investigation reports by the Accident Investigation Board. A detailed investigation of a similar matter is reported in investigation report B 1/2000 Y Collapsing of Ceiling of Supermarket at Pudasjärvi on 27 December, 2000. In that accident, the structure and the causes were mostly the same as in this accident in Sysmä.

The Ministry of the Environment has started several projects to improve safety after this building was built. Many organisations and companies working in the construction industry have participated in the projects. Practical measures among other things have been the new detailed Land Use and Building Act, researching extracting forces of nails, setting up a co-operation group for those operating in the building industry, appointing a co-ordinator, monitoring improvements in safety, and several letters to municipal building inspectors.

The investigation board wishes to remind the construction industry that safety must be a permanent part of work for everyone working in the industry.

The summary, introduction and the legends for the figures in the report are also in English.

B2/2005Y Report (pdf, 2.48 Mt)