Colin Williamsis a chartered surveyor, chartered environmentalist and a director of WCK Design and Conservation, which specialises in sustainable design and energy conservation. He has been involved in the design, construction and supervision of masonry structures for over 40 years. His research into the viability of earth block masonry as a contemporary material was carried out at the University of Plymouth. Steve Goodhewis Professor of Sustainable Technology at Nottingham Trent University, and has been researching in situ monitoring of building performance for over 15 years. He has authored many academic and professional papers on the thermaland moisture-related properties of sustainable building materials and buildings. Richard Griffi thsis now a research fellow at Nottingham Trent University, recently at the University of Plymouth. While in the School of Architecture and Design at Plymouth, Griffi ths was involved in teaching and researching the areas of architectural energetics, conservation and sustainability. Linda Watsonis a registered architect and programme leader of MA Architectural Conservation at the University of Plymouth. Her research area includes indigenous building materials and traditional construction techniques. Currently she is interested in the retrofi tting of the historic building stock and the risks this entails.Correspondence: Richard Griffi ths , Nottingham Trent University, School of Art, Architecture and the Built Environment, Burton Street, Nottingham, NG1 4BU, UK E-mail: richard.griffi ths@ntu.ac.uk ABSTRACT This article examines the possible use of earth block construction in the United Kingdom. The current and historical trends and distribution patterns of earth building in the United Kingdom and selected overseas countries are reviewed. The rationale for earth building is established, and the unique elements of earth block construction are identifi ed. Economic and technical aspects of building with earth blocks are examined, and the cost of this process is highlighted as one of the major factors that is preventing the wider use of the technique. Methods of reducing the cost of building with earth blocks are examined, and the use of thin bed mortars is advocated as a possible way of reducing the labour cost of building, thereby making earth block building more economically viable. The article examines the structural questions raised by substituting traditional thick joint mortars with earth slurry mortars, and the thermal aspects of earth block walling are discussed. The article supports earth block walling as a sustainable alternative to more traditional walling construction.

PurposeThe purpose of the paper is to explore the structural feasibility of substituting traditional thick joint mortars with earth slurry mortars modified with varying amounts of sand. Thin jointing of earth blocks would reduce the cost of sustainable earth construction.Design/methodology/approachCompressive strength of earth‐block cubes was determined. Flexural strength was measured using the BRE electronic bond wrench, which enables block couplets to be tested quickly and accurately. Three samples of earth block, one from southwest England and two from East Anglia, together with nine examples of earth slurry mortar jointing were studied, including the effect of reinforcing the joint and or the block using hessian.FindingsThe 28‐day cube characteristic compressive strengths were determined for Appley soil, Norfolk lump and Beeston soil, the last with 0 per cent sand, 25 per cent sand and with 25 per cent sand with hessian. The flexural strengths of Appley and Beeston earth slurries were determined, along with Thermalite thin jointed cement and cement mortar for comparison. The Beeston soil flexural strength increased with increasing sand content. Earth slurry with 40 per cent sand and hessian present in the joint gave the greatest strength. It is important to use blocks and slurry mortars of the same soil. Extruded and compressed earth blocks are best suited to slurry jointing.Originality/valueThis work successfully demonstrates the structural feasibility of carefully reducing the thickness of earth mortars when constructing sustainable earth block walling. Characteristic flexural strengths are suggested where the test results were sufficiently consistent, and of a magnitude likely to be useful in design.

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