Moisture meter errors: this article lists the common sources of errors (including simple mistakes in application) when using a moisture meter to measure building materials or to screen a building for hidden leaks, water, or moisture.

This article series explains the use and reliability of different types of moisture detection equipment to find water entry problems on buildings. We demonstrate where moisture meters work successfully and where (and why) they don't.

Common Sources of Error When Using a Moisture Meter

In addition to the more subtle moisture measuring errors and troubles discussed in MOISTURE METER STUDY, we list here some typical sources of moisture meter error, adapted from the owners manual for the Tramex Compact Moisture Meter for Wood.

Photo at left, the Tramex Compact Moisture Meter.

• Calibration: failure to perform a calibration check and battery check before using the instrument
• Contaminants in the material being measured: anything that changes the electrical conductivity of the material from its original state can affect a moisture measurement that depends on electrical resistance (all pin type meters and at least some electronic moisture meters).
  
  Examples are salts deposited in the material from a long history of water passage or leaks, wood preservatives or pesticides or other treatments.
• Distance: as our study above demonstrates, if scanning building cavities for leaks and moisture, the cavity or insulation may be quite wet but too distant from the sensor to provide a reading.
• Paints & coatings: a pin type and some electronic type sensors may be affected by conductive paints or coatings on the surface being measured
• Presence of other materials: a moisture sensor may be detecting metal from foil faced building insulation, metal lath, water pipes, electrical wiring, etc.
• Time since the water leak or wetting event: when testing a material or building cavity for leaks or moisture, a prior leak, even severe flooding bad enough to have produced significant hidden mold contamination, will not show up as moisture at all if the cavity and its contents are dry at the time of testing. When measuring moisture to decide if painting is advisable this is not necessarily an issue.
  
  When measuring moisture as a "mold scan" or to look for hidden rot, insect damage, or a history of building leaks and damage, this is a key limitation in moisture meter use.
  
  Therefore, relying only on moisture meter readings to estimate building leaks, building leak history, and hidden water-related damage, without also performing an expert visual inspection of the building exterior and interior, and without taking note of the building's leak history, would be an unreliable approach.
  
  At MOISTURE METER STUDY we explain this key factor in erroneous use of moisture meters in buildings.
• Scale: choose a moisture meter designed for measuring the type of material being tested; for a moisture meter with multiple scales, be sure to select the appropriate scale, e.g. Concrete, Plaster, Wood.
• Surface moisture: the moisture meter may be misled by unimportant surface moisture on the material being tested, confusing surface moisture for actual moisture within the material.
• Temperature: moisture meter readings of some materials, including wood, are impacted by the temperature of the material being tested. Typically the moisture meter is calibrated for 20C or 60F. Higher temperatures produce higher moisture "readings". The manufacturer of your moisture meter may provide a temperature correction table to adjust the reading for accuracy when appropriate.
  
  For example, for the Tramex Compact Moisture Meter (photo at above left), depending on temperature, the moisture content percentage reading may need to be adjusted by a figure ranging from -12 to + 15 %.

• Wood species: when measuring moisture content in wood, variations in wood density and species-related composition affect the wood's electrical resistance and thus the moisture reading obtained. Even the same wood species but from different places of origin may behave differently. A moisture meter manufacturer of an instrument intended for accurate moisture measurement in wood may provide an adjustment table. Wood species are collected into groups by species properties and a moisture meter correction figure will be provided for each group.
  
  For example, for the Tramex Compact Moisture Meter (photo at above left), six wood species groups are defined and moisture adjustments for wood species by group range in percent (on the meter moisture content scale) from about 0.3% to 3%.

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Continue reading at MOISTURE METER CHOICES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• MOISTURE METER STUDY
  • MOISTURE METER ERRORS
  • MOISTURE METER CHOICES
• PLUMBING LEAK DETECTION METHODS
• PLUMBING LEAK DETECTION & SHUTOFF DEVICES
• SEWER LINE LEAKS & ODORS
• THERMAL IMAGING, THERMOGRAPHY
• WET, DEFINITION OF
• WOOD BEAM ROT ASSESS: MOISTURE METERS

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MOISTURE METER ERRORS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING MOISTURE

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