A detailed investigation into the engineering properties and challenges affecting the potential introduction of a UK grown dowel-laminated timber floor panel into the domestic construction market

Satisfying the demand for more efficient and sustainable buildings presents a considerable challenge to the UK construction industry. Increasingly, the UK construction industry is looking towards prefabricated or offsite construction as a means of providing economic, sustainable and energy efficient buildings. Timber and engineered wood products (EWPs) are ideally suited to take advantage of the trend towards off site construction. However, in the UK, planted commercial tree species, are only used in a limited fashion by the UK construction industry as it is generally perceived to be of low quality. Forestry projections indicate that within the next 10 to 15 years there will be an abundance of UK timber as large amounts of standing stock reach maturity. Subsequently, there is a need to fully utilise the available and future resource, lest large amounts of commercial timber and capital will be underutilised. This has led to more research being conducted into new or novel methods of maximising the potential of the existing and predicted UK timber stock. Whilst the production of a variety of EWPs have been embraced on the continent by small to medium enterprises working in the timber industry similar developments in the UK have been less forthcoming. One such product that has been developed on the continent is Brettstapel, Dowellam or Dowel laminated timber (DLT). These are solid timber panels that are formed without the use of adhesive and rely on hardwood dowels to join the single laminations together to form a panel. The creation of an engineered timber product without synthetic adhesives allows for a real reduction in the energy used to create a higher value EWP that can be produced in a variety of shapes and finishes. Building upon the research of the Centre for Offsite Construction and Innovative Solutions (COCIS), this thesis explores the development of a DLT panel formed predominately of UK grown timber. A ground up approach to developing a DLT floor panel was undertaken; this included identifying market opportunities, locating avenues for its application and determining barriers to its implementation. One of these barriers highlighted within a market study was the lack of technical information and guidance. The provision of technical information for the panel incorporated a staged analysis of materials and structural mechanisms within a panel that defined its structural performance. These included the determination of the pertinent mechanical properties of the softwood laminations and hardwood dowels including combined timber embedment properties to determine the most appropriate materials to be used in a panel. An experimental investigation into the use of hardwood beech dowels in conjunction with UK Sitka spruce and larch members in double and multiple shear plane connections is also undertaken. The findings for the study are integrated into a process for the design and verification for UK DLT panels. Through a series of experimental tests conducted on UK grown and produced DLT panels the thesis demonstrates that UK grown timber could be used to create DLT panels in the future. However, the position of the dowel and the overall stiffness of the all-timber connection cannot ensure a composite panel with improved performance is created. Finally, the thesis demonstrates the potential for the UK production of DLT panels by presenting a case study for a new build property in the Scottish Highlands that utilises UK softwood and information obtained in this study.