Long-term monitoring of a historic building to evaluate wall moisture content changes due to capillary rise

When impermeable ground bearing slabs are installed in buildings without a damp-proof course, it is believed that ground moisture will be ‘driven’ up adjacent walls by capillary action, however there is limited evidence to test this hypothesis. An experiment was used to determine if the installation of a vapour-sealed ground floor in a historic building would increase moisture content levels in an adjacent rubble-fill wall. This was achieved by undertaking long-term measurements of wall, soil and atmospheric moisture content over a three-year period. Measurements taken using timber dowels showed that the moisture content within the wall did not vary in response to wall evaporation rates and it did not increase following the installation of a vapour-proof barrier above the floor. This indicates that the moisture levels in the rubble-fill wall were not driven by capillary rise.