Moisture sensor for structures and building materials

Thanks to its segmented and elastic design, this sensor permanently and reliably detects the electrical resistance in building materials. This provides precise information about the moisture content in the material.
This new moisture sensor detects electrical resistance along its entire installation length. This gives definite conclusions about the moisture content of the monitored building material in different layers of depth. The sensor is suitable for instantaneous as well as long-term measurements in structures made of wood and concrete in particular. Problem areas and risks, such as moisture-induced reduction of compressive and flexural strength, will be detected at an early stage, preventing damage.

Due to its elastic design, the system is suitable for permanent stationary use even in dynamic materials. The design uses elastic electrodes, which enable reliable contacting of the building material over the entire borehole despite material shrinkage or swelling caused by drying or wetness. It records the moisture content in all layers over the length of the installation. Due to the segmented design, the sensor measures the electrical resistance between each zone. Sensors are suitable for permanent building monitoring over long periods of time if they are additionally equipped with a commercially available high resistance measuring device and the possibility of sensor data export (e.g. via radio or WLAN).

The fundamental difference to current hammer-in electrodes on the market: These provide values for a single depth and require at least two boreholes at a defined distance. Multi-ring electrodes made of metal known up to now do not compensate for shrinkage (especially with wood materials). Thus, these sensors are hardly suitable for long-term measurements, since varying contact pressure or even a lack of contact falsify the results or measurements become unusable. Renewed moistening of the building material remain undetected. Unintentional slide out of the sensor from the borehole is prevented.

• Compensates for material shrinkage

• For measurements in wood, wood-based materials, concrete, anhydride, plastics and many more.

• Short-term measurement or permanent monitoring

• Easy handling and installation

• Multi-layer measurement over the depth of installation

The invention was developed at the Chair of Timber Structures and Building Construction at the Technical University in Munich. The maturity of the development is far advanced. Several prototypes exist, some of which are in long-term use. Technology Readiness Level: TRL 7