Non-Invasive Moisture Meters: Fast, Efficient and Hassle-Free
January 8, 2013
It is important for a water damage restoration specialist to establish the source and extent of the moisture damage that has occurred. The best way to achieve this is with a moisture meter.
Moisture meters come in two main types: invasive and non-invasive.
Invasive, or pin-type, meters operate by penetrating the surface with metal pins to measure the resistance of the material in the space between them. This method of testing was developed for measuring the moisture content of timber, but is arguably problematic for large areas of walls and floors where pin holes may be unsightly, especially in materials such as drywall and in solid surfaces where the pins cannot penetrate. Taking a reading from the surface of such materials can be misleading, as the surface may be dry due to low humidity. However, below the surface the material or substrate may be wet.
That’s where non-invasive moisture meters come into play, specifically those that work on the principle of impedance measurement using direct contact electrodes and have been adapted to the needs of various industries over the years. Direct contact electrodes offer more accurate results, more versatility, more depth of signal penetration and reproducibility of readings than other non-destructive moisture measurement instruments.
Non-invasive, or pad-type, impedance meters operate by pressing contact electrode pads against the surface, which send a signal into the material and display the extent of moisture on the analog or digital display. The obvious benefits of this system for building inspection is the ability to cover a large area in a short time frame, as well as leaving no unnecessary further damage to the property.
Some instruments offer three scales for different building materials. Readings taken on wood, using the wood scale, are measurements of moisture content by percentage. Other scales for brick/masonry and drywall/roofing are comparative and must be viewed in relation to each other.
For the purpose of establishing the extent of moisture damage, it is useful to map the area using a grid-style approach which allows for a meaningful comparison to readings taken at a later stage of the restoration process.
Beginning by taking a reading of each material in an unaffected area, where possible, is helpful in establishing a “dry-goal” measurement, which will be the target reading for affected areas after the process is complete.
More advanced moisture meters offer the ability to connect to a range of wood probes as well as a relative humidity (RH) probe. This switches the instrument automatically to hygrometer mode, for readings of temperature, relative humidity, dew point and mixing ratio, all of which provide indispensible information for a thorough building inspection. Having these readings for each survey will give a greater insight into the overall ambient building conditions.
For instance, inserting the RH probe into a wall in a specially drilled hole in an affected area allows the user to take in depth ERH (equilibrium relative humidity) measurements deep into the wall.
Another important tool is a concrete moisture meter, which is designed to give actual percentage moisture measurements by weight in concrete slabs and screeds, giving the inspector valuable information as to when the concrete floor is suitably dry to accept a floor covering. These readings are also non-invasive and instant and are an ideal way to plot the best location and time to install relative humidity tests when required to conform to ASTM standards.
A non-invasive moisture meter is also a must-have tool for the infrared thermographer, who can use it to confirm suspected moisture damage.
Because thermal imaging cameras do not see moisture but instead see temperature differences which may appear at first to be moisture but, on further inspection, turn out to be an insulation problem. This makes them ideal partners.