ALASTAIR W.STUPART AND IAN H.MURRAY Building Research Establishment, Scottish Laboratory

Water repellents can be considered as a remedy for rain penetration but information is required on their effectiveness and durability. In the UK water repellents are assessed by BS6477:1992 which tests individual building units (for example bricks). However, realistic tests should take into account the effect of mortar joints and simulated driving rain. The results of testing considered as possible improvements to BS6477 are described. A spray test developed by BRE simulates severe driving rain. The results clearly identified differences in water repelling ability between groups of treatments. Aluminium stearate and acrylic polymer treatments deteriorated. Some silicone based treatments showed an increase in water repellency. Assessments of treated brickwork samples exposed naturally in a severe location showed that certain treatments can allow the accumulation of moisture leading to frost damage in susceptible materials.