In Situ, Non-Destructive Testing for Evaluating the Role of Pointing Mortar in Preventive Conservation Strategies. A Case-Study on Reigate Stone at the Wardrobe Tower, Tower of London

The correct choice of pointing mortar is considered crucial to the conservation historic masonry. A proliferation cement and eminently hydraulic lime mortars since late 19th century has accelerated deterioration built cultural heritage in many parts world. Whilst use softer, lime-based stone now common practice, their role overall strategy highly vulnerable building stones such as Reigate Stone requires assessment. In this paper non-destructive testing (NDT) used across a two-year period investigate impact different types situ. NDT data on surface hardness moisture are interpreted at scales assess regulation masonry Wardrobe Tower, ruined structure Tower London, following repointing carried out Spring 2017. Joints repointed using (NHL3.5) shown regulate adjacent blocks less well than those putty mortar. However, despite an initially inappropriate recipe, older some instances perform similarly mortar, suggesting that NHL can weather sympathetically. results also indicate that, whilst type does play individual stones, its effect outweighed by both properties itself, strength past decay, wider micro-contextual factors, exposure or topography. Findings from only plays part regulation; enable effective functioning minimise need for repeated interventions, it may be necessary take additional protective measures mitigate ingress, water run-off channelling heavy rainfall. implication Stone, sustainable strategies must incorporate broad appraisal of, tailored response to, specific decay mechanisms. With careful calibration survey campaigns, collected situ inform within strategies.