A Comparative Evaluation of Methods to Monitor Moisture in Historic Porous Masonry Materials
Author(s): Heather Viles, Hong Zhang, Scott Orr
The project aimed to develop a methodology to compare the performance of a range of invasive and non-invasive moisture measurement methods used to assess moisture in porous masonry. This methodology was laboratory-based and used test blocks of common traditional building materials (limestone, sandstone, brick and lime mortar) under controlled conditions of drying and wetting. The performance of each method tested was compared against weight measurements, which give absolute measurements of moisture content – often called the gravimetric method. Experiments were also carried out to evaluate the influence of drying conditions and block size on the test results. A variety of non-invasive handheld moisture measurement devices were tested, including commonly available resistance, capacitance and microwave moisture meters. Also tested was a range of invasive methods, including wooden and ceramic dowels, relative humidity sensors and time domain reflectometry (TDR) probes. For some of the non-invasive methods, further experiments were designed and carried out to evaluate the depths to which they could measure saturated parts of otherwise dry blocks of sandstone and limestone. A simple experiment was also designed to measure the depth to which some of the non-invasive methods could sense metal objects in otherwise dry materials. This was used to evaluate whether the presence of metal in historic walls could affect the moisture measurements obtained. Finally, a short field monitoring exercise was carried out to explore the usefulness of both non-invasive and invasive microwave moisture measurements in comparison with conventional wooden dowel surveys.
- Report Number:
- 2/2022
- Series:
- Research Report
- Pages:
- 112
- Keywords:
- Ground Penetrating Radar Mortar Traditional Construction Water Brick Monitoring Moisture Moisture Meter Damp Humidity Temperature Relative Humidity Moisture Content Wetting Drying Moisture Measurement invasive Non-Invasive Resistance Meter Capacitance Meter Microwave Meter Time Domain Reflectometry Limestone Sandstone Porous Masonry Porous Historic Building
