S1/2006Y Building accidents in the late winter of 2006
Several incidents of roof and ceiling damage occurred in Finland in the late winter of 2006, within a relatively short period, and primarily in hall-like buildings with a potentially large number of people indoors. The most serious incident occurred in Haapajärvi on 8 April 2006, where approximately 350 m2 of supermarket roof and ceiling collapsed during the store’s opening hours. In addition, the collapse of a riding hall in Veteli the next day had the potential to cause serious personal injury, but took place at night when nobody was present. Other cases of damage chosen for accident investigation were more minor. They occurred in Pihtipudas on 20 March and 2 April, in Laukaa on 3 April, in Karjaa on 5 April, in Keitele on 7 April, in Jyväskylä on 8 April and in Joensuu on 15 April.
None of the investigated cases resulted in personal injury. Rescue staff or units visited all of the accident scenes. The incidents posed no challenge to rescue operations, since the operations mainly comprised the determination of the situation and prevention of any further damage. For instance, the prevention of further damage comprised the removal of snow, with supporting structures remaining standing, and the isolation of the affected area.
The immediate technical causes of the incidents were divergent. In Haapajärvi and Veteli, the support of long trussed rafters was insufficient, and in Veteli, the entire horizontal stiffening of the building was defective. In Pihtipudas, the plywood joints of locally made trusses failed. In Laukaa, as the glued laminated beams dried and shrank, they became supported by screws only on the upper edges, and due to the heavy load of snow, fell back into place. In Karjaa, the defects were due to the method of fastening prefabricated sandwich elements of the façade. In Keitele, the glued laminated beam originated from the 1950s and the old gluing of the beam failed. In Jyväskylä, snow gliding down the arched roof formed a snowdrift, pressing in the corrugated sheet steel of the roof, whereas in Joensuu, the roof outlet had become blocked and the corrugated sheet steel failed due to melt water accumulating near the outlet.
A common denominator in all cases except one was that all buildings were designed and built while the old Building Act was effective, and structural safety development measures undertaken in the last few years did not apply to them. Inspections of existing buildings, performed in 2004, did not involve the buildings investigated. In most cases, the defects of the buildings could have been identified by expert inspectors. The current problem with existing buildings is that if defects with an impact on safety have not been identified during construction, they will often not be identified at all until the structures are damaged.
In order to avoid damage similar to the incidents investigated, the investigation commission recommends that an inspection procedure be established for buildings, with its main focus on structural safety. Moreover, the investigation commission recommends that municipal building supervision authorities should be pooled into larger entities, in a manner similar to rescue operations, so that each regional building supervision authority would have adequate special expertise for the supervision and monitoring of various kinds of buildings and structures. In order to manage the overall safety of buildings, the investigation commission recommends more comprehensive co-operation between building supervision, industrial safety and the rescue authorities. As regards buildings constructed using trussed rafters, the commission recommends that buildings with trussed rafters of a span of over 15 metres be defined in the National Building Code in category AA instead of category A, which would place stricter requirements on the designer’s education and qualifications.