H+R were instructed to determining the probable construction and condition of the plaster on the chapel walls, to identify defects in the wall plaster, and to contextualise these defects with reference to physical sampling including gravimetric analysis of available moisture content, hygroscopic moisture content, and presence of hazardous content such as anthrax within the animal hair binder. The goal was to determine the likely source of water penetration which was resulting in detachment and deterioration of the plaster in areas identified during previous investigations, and to provide a suitable and sympathetic remedial strategy going forward.
Physical core samples of wall plaster were taken from representative areas for subsequent analysis in the laboratory. Masonry samples were also taken for analysis at high, medium, and low levels throughout the chapel to understand the extent of retained moisture within the wall masses. For non-invasive testing, the lower wall areas of the chapel were divided into a grid of 500mm resolution from 150mm above floor level to 2150mm, and measurements recorded at each grid point with an electrical meter using two different probes with differing measurement techniques. Each of the probes uses microwaves penetrating to an approximate depth of 300mm. Capacitance readings were also taken for later cross-reference.
How we solved the problem
Results from microwave and capacitance readings are inherently relative, but when cross-referenced with physical sampling can provide a deeper understanding of the extent of available and hygroscopic moisture content, and can also be visually mapped for easier comprehension. These techniques enabled H+R to identify the root cause of the issue as well as providing the client with a suitable and sympathetic remedial strategy reducing the risk of further issues affecting the historically significant fabric of the building.