Description and testing of three moisture sensors for measuring surface wetness on carbonate building stones

Abstract

Three moisture sensors were tested as a means for determining the surface wetness on carbonate building stones exposed to conditions that produce deposition of moisture. A relative-humidity probe, a gypsum-coated circuit grid, and a limestone-block resistor were tested as sensors for determining surface wetness. Sensors were tested under laboratory conditions of constant relative humidity and temperature and also under on-site conditions of variable relative humidity and temperature for eight weeks at Newcomb, NY. Laboratory tests indicated that relative humidity alone did not cause sensors to become saturated with water. However, the rates of drying indicated by the sensors after an initial saturation were inversely related to the relative humidity. On-site testing of the relative-humidity probe and the gypsum-coated ciruit grid indicated that they respond to a diurnal wetting and drying cycle; the limestone-block resistor responded only to rainfall.

Methods for determination of duration of surface moisture and presence of water in gaps in wood joints

“…Norberg (1999) used a surface moisture sensor where the time of wetness was monitored on the sensor surface. See et al (1988) used two methods to monitor surface moisture on carbonate building stones; one leaf wetness sensor with a gypsum coating and one sensor of their own design. This sensor consisted of electrodes mounted on both sides of a piece of limestone.…”