ALASTAIR W STUPART*JAYA S SKANDAMOORTHY**and FRANK EMERSON***
*BRE Scottish Laboratory**BRE Centre for Masonry Construction
***Tilcon (South) Limited
Lightweight mortars contribute to reduced heat transmittance of walling by their low volume densities, hut at present are not used in the UK. The results of a test programme utilising the one lightweight mortar product available in the UK are described. Compressive strengths met the minimum requirements of BS 5628 but the characteristic flexural strengths of wallettes were below those required. Test results using a derivative product currently under development are described and show improved compressive strength and durability. Both mortar types are shown to reduce the U-value of a typical cavity wall by approximately 8%.