Design of safe timber structures - How can we learn from failures in concrete, steel and timber ?

Eva Frühwald, Erik Serrano, Tomi Toratti, Aarne Emilsson, Sven Thelandersson

Research output: Book/ReportReport


In the present report an investigation of failures in buildings with timber as a primary structural material is presented. The concept of failure considered here is mainly related to the ultimate limit state and is defined as events which have or could have implied risk for human lives. A total of 127 failure cases were included in the survey. The data material used in the project was collected partly from direct information on failure cases provided by project participants who had been assigned to investigate failures and partly from cases documented in literature. The case reports were analysed and causes behind the failure event were classified with respect to the following nine categories: 1. Wood material performance 2. Manufacturing errors in factory 3. Poor manufacturing principles 4. On site alterations 5. Poor design/lack of design with respect to mechanical loading 6. Poor design/lack of design with respect to environmental actions 7. Poor principles during erection 8. Overload in relation to building regulations 9. Other/unknown reasons The most common cause of failure found in the investigated cases is poor design or lack of strength design (41%). Other important failure causes are poor principles during erection (14.1%), on-site alterations (12.5%) and insufficient or lacking design with respect to environmental actions (11.4%). In total, about half of the failures are related to design. About one fourth of the failures are caused at the building site (on-site alterations, poor principles during erection). This means that wood quality, production methods and principles only cause a small part (together about 11%) of the failures. The problem is therefore not the wood material, but engineers and workers in the building process. This picture is similar to that found from other failure investiga-tions for other types of structures (mostly steel and concrete), where human errors were found to be the dominating cause behind failure events.
Original languageEnglish
Number of pages222
Publication statusPublished - 2007
MoE publication typeD4 Published development or research report or study

Publication series

SeriesReport TVBK


  • timber structure
  • failure
  • human error
  • workmanship


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