Article | Moisture Meters – Wood Moisture WHAT?

Concrete & Wood Moisture Meter Science Simplified (Slightly)!

(A starting point more directed at the emerging flooring industry than those already in-the-know)

Moisture meters…we know we need them or should have them, but do we really even understand them?

In my time as an inspector and technical advisor, I have come across many professional installers, retailers or building personnel who do not even have a moisture meter. If they do have one they have never actually taken the time to fully understand how it works or what it’s actually telling them, let alone train their staff on how to use one correctly.

If you are wanting to evolve and differentiate yourself from the highly competitive market, then maybe it’s time to step up and commit to quality and detail that will distinguish you from the sea of sameness. Remember, your client has Google and a lawyer when things go wrong. Failures are costly and, unfortunately, more often than not, blame gets directed at the installer first. This is not about pointing fingers. This is about fully committing and leveling up to be a professional and deliver expertise.

Getting into the science of flooring can be a bit scary and intimidating, especially for those who have climbed up through the informal ranks of life experience and have never really taken the time to research the inner workings of moisture and heat. You kind of just know what you know, right? While you don’t need a scientist’s perspective, a basic understanding of these base concepts will quickly accelerate you on your way to safeguarded installs.

Due to different types of moisture meters working in different ways, it’s always best to determine your particular industry genre’s best go-to option, and in some cases, this may mean getting two or three different meters depending on material requirements.

Let’s break this down into two main sub-sections for ease of clarity:

  1. Handheld Non-Invasive Concrete Moisture Measurement and Comparative Screed Assessment

These systems such as the well-known Tramex CME4 commonly calculate moisture percentages in concrete by measuring the variable conductivity of the cementitious material. Obviously, the volume of conductive moisture and density of the material impacts the impedance of the meter’s low frequencies and calculates the respective reading. Much along the lines of an electrician’s multimeter. Electrical impedance moisture meters generally read moisture levels from 20 to 40mm below the surface. With these units being calibrated for concrete, results shown are the actual concretes moisture percentage. For other variable density cementitious materials, like screeds, the indicated results are only a comparative value and do not reflect actual moisture content percentages. This is where things can really go wrong if you are having to defend yourself and your work when a floor has failed.

It is highly recommended to fully understand what your preferred product supplier’s warranty requirement is prior to committing to a moisture meter. While budget moisture meters may be attractive, do they service your actual need, and will they be recognized by an official third-party inspector and manufacturer’s warranty?

  1. Handheld Invasive Pin Moisture Measurement and Wood Moisture Equivalent Assessment.

All meters have been calibrated to a single common median of measure and then generally have a reference chart for alternative materials or in the case of timber, variable species densities. When using a Protimeter Mini, the initial readings display the actual wood moisture percentage. A calibration chart is provided to cross-reference reading versus species variable. For materials other than wood, your reading is called that of ‘wood moisture equivalent’. This is the term whereby if the wood was placed alongside that which is being measured and left to acclimate to ‘wood moisture equilibrium’, then the moisture content of that piece of wood would be as indicated. Again, the reading is not the moisture percentage of the item being measured but that of a supposed piece of timber being in exclusive contact and acclimating to a state of balance with it. Again, this is where users of these tools get confused because they believe the percentage reading is that of the slab of concrete which they are measuring, which it is not. Unfortunately, on these meters, a green light does not always mean go.

Now, earlier I mentioned Equilibrium Moisture Content (EMC). Maybe it’s worthwhile having a quick refresher on what this is and why it’s so important…

Think of that front door of yours that sticks in winter, catching on the door jamb versus being free-flowing and problem free in the summer. I’m assuming your winter is wet and rainy like mine and that the rain does not hit it directly. The door has absorbed moisture in the air during the rainy season when the relative humidity (RH) is higher and now it catches on the door frame. The reverse happens in the summer when the RH is lower, and the door shrinks, negating this issue. This process of absorption and expulsion of moisture in tune to the RH and environmental temperature is called EMC. Yes, it’s a thing and yes someone else can explain it a whole lot better than me. It is however well worth Googling it and brushing up on this essential phenomenon as it impacts floors and how we respond to them as professional installers. As long as the environment changes, so will any natural material like wood adjust its moisture content to balance with that of its environment.

“The equilibrium moisture content of a hygroscopic material surrounded at least partially by air is the moisture content at which the material is neither gaining nor losing moisture. The value of the EMC depends on the material and the relative humidity and temperature of the air with which it is in contact.” Wikipedia

Moisture meters are an essential component of a floor professional’s kit… it’s not debatable.

In this quest to demystify these tools, I recently spoke to Graham Duk of of Africa’s leading suppliers of technical instrumentation and more importantly a moisture meter techie. Check out the video below. It’s a great way of getting more insight.

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