Moisture dynamics in an historical masonry structure: The Cathedral of Lecce (South Italy)

Dampness is the main cause of masonry deterioration in many historical buildings but moisture behaviour is often difficult to understand. This is partly due to the complexity of moisture models which are rarely applied in monitoring plans. This paper reports the modelling of the moisture dynamics of the Cathedral of Lecce and its below ground Crypt (South Italy). The aim of this study is to give insights into moisture dynamics in buildings in order to overcome knowledge gaps in the field, such as those related to the estimation of the drying capacity of a microenvironment. The sharp front (SF) theory was used to analyse the main processes involved in rising damp. Moisture transfer dynamics were investigated to and from the walls and columns constituting the Cryptʹs masonry by first considering a steady state of balance between the water absorbed by capillary forces and that lost by evaporation. A varying state of non-equilibrium was then treated deriving simplified formulae to calculate indoor and outdoor evaporation rates. The model was validated with experimental surveys and site evaporation measurements. The paper shows that many physical quantities (e.g. height of the rise, capillary rise, water stored, drying flow rate, time-scale for drying) can be calculated and modelled over time using formulae that involve commonly available microclimatic and meteorological data (e.g. temperature, relative humidity and air speed). The information obtained can help to understand the periodic moisture behaviour leading to an explanation related to deterioration process dynamics. The results are useful for masonry maintenance.