*University of Newcastle **Particie Parsons Ltd, Newcastle upon Tyne

Defects in old rubble-filled walls sometimes develop as bows or bulges in one or both outer leaves. These can be the result of rainwater penetration, or repetitive cycles of freezing and thawing. Several modern methods are now available to investigate the material and construction within a wall; a technique using radar provides reliable results with minimal disruption or hazard to public health and safety. A case study is provided in which radar was successfully used to determine the nature and extent of structural problems within a rubble-filled wall, leading to economic and sympathetic repair in a sensitive architectural conservation area.