Excess water is a problem
The first stage is to understand the type of water you are dealing with. Electrical meters measure moisture levels in timber, providing accurate readings.
The two main types of electrical moisture meters are:
The conductivity meter uses two pins and measures the conductivity field between them on the surface to be tested. This gives the wood’s moisture content as a percentage in timber, which is quantitative.
Capacitance/impedance meters use radio waves to measure depths 10-19mm below the surface. This method, often called ‘search mode,’ enables rapid assessments.
| Timber %WME | Relative Readings | |
| Protimeter Surveymaster | 5% to 99% | 70 to 999 |
| Flir MR77 | 0% to 99% | 0 to 100 |
| Tramex ME5 | 5% to 30% | 0 to 100 |
In most building materials, pin readings are relative and do not directly measure moisture content. Inaccurate search or scan modes may lead to misdiagnosis. Combining both methods provides a comprehensive assessment of dampness.
Salts present in the building structure can elevate electrical moisture meter readings, suggesting a potential historical issue.
An educated eye can discern patterns of damage caused by dampness. An electrical moisture meter can provide valuable assistance. Scan mode meter readings must be used with caution. It is advisable to engage a qualified professional for thorough inspections.
| Possible dampness | SKB | 250 | 500 | 750 | 1000 | 1250 | 1500 | 1750 |
| Ineffective damp-proof course | >25% | 95 | 90 | 90 | 85* | 10 | 0 | 0 |
| Plaster bridging or condensation behind skirting | >20% | 75 | 0 | 0 | 0 | 0 | 0 | 0 |
Depth of moisture meter pins, 2-3mm into the surface.
Using Deep hammer probes
The moisture meter pins give a % reading of the timber’s surface. A deep hammer probe is necessary to measure moisture levels in larger timber. This probe measures moisture deeper within the timber, allowing comparison between surface and deeper readings to guide any necessary remedial measures.
Deep probes into masonry
Drilling two 5mm holes into the masonry. The probes will provide a relative reading and help diagnose dampness.
Calibration of the electrical moisture meter
For a resistance meter, there is a testing wire that you place on the pins. This confirms that the device is working correctly. Tramex supplies a calibration plate.
Key Takeaways
- Understanding the type of water is crucial for accurate moisture assessment with electrical moisture meters.
- There are two main types of electrical moisture meters: conductivity meters and capacitance/impedance meters, each providing different insights into moisture levels.
- Combining both meters provides a comprehensive assessment of moisture while accounting for potential inaccuracies.
- Using deep hammer probes can measure moisture levels in larger timbers, providing depth insights that surface readings alone cannot.
- Calibrating the electrical moisture meter is necessary to ensure accurate readings; a calibration plate is available for verification.
