Development of new approaches to moisture content measurement for building materials

The measurement of moisture in building materials has been of importance to building professionals for many years to aid the diagnosis of the nature and cause of building defects. Measurements of moisture content of the building fabric are often carried out on elements where there is uncertainty about the material composition, uncertainty about the dimensions of individual components, and where there is an existing problem there can be some degradation of the materials themselves. Accurate measurements of the moisture within such walls present many challenges. Research has been undertaken to evaluate the practical application of three relatively new techniques in building science: dual probe heat pulse method; time domain reflectometry; and more sophisticated electrical approaches. Although these techniques have been used in different sciences, the application to actual buildings can present a challenge. This paper details the development of these techniques from theoretical concept through to a practical technique successfully applied for real measurements. The techniques have been calibrated against X-ray absorption measurements using materials of well-defined properties such as sandstone and autoclaved aerated concrete. This calibration allows absolute measurements of moisture content to be made. Finally the paper explores the practicalities of using these approaches for in-situ measurements and identifies particular opportunities and limitations for future application. © 2009 WIT Press.