Structural Characteristics of Load Bearing Straw Bale Walls

Straw bales offer a renewable and affordable construction material suitable for a range of uses as both thermal insulation in walls and roofs, and for low rise loadbearing structural walls. As a co-product of food production, it places no further pressure on land use, and in common with other crop-based materials, straw captures and stores carbon dioxide through photosynthesis, offering the means to construct buildings with a net negative carbon emissions footprint. Straw also further reduces operational carbon emissions by virtue of its excellent thermal resistance. However, despite these benefits, and a successful construction history extending over 100 years in many countries worldwide, straw bale construction has still to make a major commercial impact in the wider construction market. Limited technical understanding of some fundamental performance characteristics (including structural capacity, hygrothermal behaviour, and durability), absence of technical standards, and a lack of certification and product warranty for straw bale, still remain barriers to wider acceptance. In this paper results are presented from a study on full-scale straw bale walls to evaluate the structural performance under vertical loading and lateral loading. The performance of identical straw bale walls, with and without plaster coats, is presented. The study is also unique in presenting on out-of-plane lateral loading and wall performance under eccentric vertical load cases. The research will support structural designers and enable wider uptake of this sustainable form of construction.