Past experience has proved that silanes type materials and, particularly high build coatings, should never be applied to natural stone as misguided protective water proofers. Short and long term problems associated with their use include excessive penetration, chemical alteration of the stone substrate, alteration of the visual aspect of the surface and low vapour permeability. A additional issue for conservation, is the degree of reversibility of the treatment, for example, silanes chemically combine and cannot be extracted. Coatings are problematic to remove, often only possible by use of abrasive blasting techniques.
Wisely, Epicuro HBG was applied to the external stonework after removal of the offending coating. This invisible nano-treatment is vapour and gas permeable and only 'semi-water-resisting'. It provides a reducing degree of waterproofing during the first 24 hours of rain and wet conditions and then, if conditions continue continue, it allow penetration. Over a period of years, the building has thus effectively been exposed to reduced total of wet weather loading, equivalent to existing in a kinder climate. Whilst not completely exempt for such, the internal water available for frost attack is also substantially reduced. At the same time, the complete wall composition remains vapour permeable i.e. is able to dry out under drying conditions. Like many other fine historic buildings, advantage is being taken of this proven protective measure.