Planning SA (Department of Planning and Local Government) have provided advice of potential for catastrophic roof truss failure in buildings constructed between 1970 and 1997, resulting from delamination of nailplates on pre-fabricated roof trusses. Council has been made aware that a problem has been identified with nail plated timber trusses manufactured between the above dates, and may particularly concern large open spans and where heavy roof loads are carried i.e. solar hot water services or tiled roofs.
Between 1970 and 1997 a number of prefabricated roof trusses were constructed using nail plates which have since proven faulty. The risk is that the nail plate, or steel connectors, used a particular form of nail which can work its way loose over time. Trusses using these faulty nail plates can potentially separate from the timber at the truss joints, and depending on the load they are bearing lead to failure of the roof structure.
Minimising the Risk
Planning SA has issued the following criteria for buildings at risk of catastrophic truss failure:
- Buildings constructed in the range 1970 - 1997, and
- Roof framing consists of prefabricated timber trusses, and
- Clear span buildings over large open spaces - particularly such as community halls, libraries, churches, clubs / restaurants / hotel dining rooms, and
- The covering is roof tiles.
Council advises all owners of dwellings constructed during this time frame to re-inspect their roof framing to verify that the nail plates are in place and not drawing away form the timber. An explanatory leaflet and a Pre-fabricated Roof Truss Check list is available from Planning SA.