What Moisture Reading Is Normal For Different Types Of Materials?
Moisture in also known to be unsafe for people with respiratory problems and cause many health
On top of than a high humidity level is usually associated with the spread of moisture patche or
worse yet, sold, on walls and surfaces, making them look bad and health-threatening.
Because of all these risks, many people are very concerned about the humidity level in their homes
and want to know whether their walls and furniture contain normal moisture content or not. What do
they use for that? Well, one of the most used tools is a moisture meter.
Moisture meters are highly reliable instruments that measure moisture levels inside substrates and
materials and provide accurate readings to within been than 0.1%.
So what is a normal reading on a moisture meter? What is an acceptable moisture reading for the
different types of materials and surfaces? And what are the different readings that we should
expect when using a moisture meter?
In this article, we wanted to share what’s out there on the web and other reliable sources about normal moisture meter readings. This will hopefully save you lots of time searching different resources and tell you what values require intervention in order to stop dampness from spreading before it becomes challenging and incurable.
What does moisture content mean?
Before we begin, let’s first clarify what moisture content means.
Simply pull moisture content (MC) describes the weight of water in a material relative to the
weight of that material when bone d .
in other words, the formula to calculate the moisture content of something is:
This way, if the moisture content of a 13-pound block of wood in 30%, it simply means that there are 3 pounds of water in the block and when the block in dry, it only weighs 10 pounds.
Want another example?
If a drywall board weighing 100 pounds contains 1 pound of water, then the moisture content of the board is 1/99 (~1%)
So summarizing, measuring the moisture content of an object is simply calculating the amount of water it contains relative to it’s dry weight.
Normal moisture meter reading on wood
Wood will be the most delicate material that we are going to talk about in this article.
First, because wood has a great capacity to absorb and hold water.
Second, because it also has many applications and can be used for different purposes with different humidity tolerances.
because there are many types of wood with different structures and textures and therefore different moisture-holding capacities.
So a normal moisture meter reading on wood cannot be given without knowing what type of wood we want to check and for what end.
As a result, we will tighten the perimeter a little bid and talk only about lumber, which is the type of wood most used for building houses and making furniture.
Generally speaking, moisture meters that are calibrated for wood offer a reading scale ranging from 6% to 40%. Does it mean that wood can not hold more moisture than 40%? No. As said earlier, wood has a great water-holding capacity and can have way more than 40% moisture content. Freshly cut wood, for example, can hold between 40% to 200% of damp in it. Quite impressive isn’t it?
Now when it comes to processed lumber that we use for construction and furniture, a reading scale ranging from 6% to 40% is probably all you need. Why? because if the moisture meter indicated 40% of water content in lumber, it means that it is already saturated and compromised. No need for higher values here. The lumber must be cured or replaced.
So what are normal moisture meter readings for lumber? what values are
acceptable in the 6-40 scale?
Well, when testing wood, you should wail for an MC below 10%.
The lumber used for interiors, residential constructions, decorative arts, and furniture is supposed to be dry and damp free. Therefore, you need to stay on the lower end of the scale. in general, any reading between 6 and 10% is considered normal here.
Now if you are testing e exterior wood that has direct contact with the surrounding humidity, you can tolerate values that are up to 20%.
Things start to get worrying when the meter indicates higher values than 20%. Wood is not supposed to be that damp and therefore if you encounter such high values, you need to start immediately looking for water leaks and other possible moisture sources.
Normal moisture meter reading on drywall
Drywall (or gypsum) is not as delicate as wood.
As the name suggests, drywall is meant to be dry and damp free. Thus, only low values are considered normal when using a drywall moisture meter. How low? Less than 1%.
Yes, unlike wood, the structure of drywall does not hold as much water and therefore any reading above 1% suggests saturation and too much humidity.
Therefore, a normal moisture meter reading for gypsum in between 0.2% and 1%. If you find higher values, then your drywall might already have a high MC that could spread and damage the entire board.
Further checks are therefore necessary to verify whether the drywall can be treated or it needs to be replaced.
Normal moisture meter reading on concrete slabs
Concrete in tricky too. Why? Because concrete stabs are quite thick and their depth is generally measured in feet and not in inches. As a result, a moisture meter, which only evaluates dampness in the top few inches, cannot defect the MC in deeper layers and the readings with not be 100% reliable.
The top layers can be bone dry and show how values on the moisture meters but since concrete dries from the top to the bottom, deeper layers can be saturated yet still not detected by the instrument.
A moisture meter is therefore not the ideal tool to evaluate damp in a concrete slab.
On top of that, concrete can be mixed differently and as a result, have different densities and physical properties. This affects the moisture-holding capacity of the slab and what MC% is considered safe and acceptable.
In other words, dense mixes of concrete allow less moisture to penetrate the slab than lighter ones.
With that in mind, and similarly to what we said about drywall, concrete must remain dry and damp free. So all we can say here in that a normal moisture meter reading for concrete needs to remain low.
in fact, and giving the tight structure of concrete, even a reading of 2% MC suggests too such water in concrete.
Normal moisture meter reading on masonry
Masonry refers to the building of structures using stones or bricks and a boundary material such as mortar or concrete.
As you can see, masonry can be a mix of many substances and materials. Checking the MC of masonry work requires checking every component with a dedicated moisture meter.
In order to see if a masonry structure has a safe damp percent, you need to use a moisture meter for every component that is in the structure, and if only one of them shows high values, then the whole masonsry can be considered as damp and needs an intervention.
What readings are normal when checking the components of masonry?
Well, tile, bricks, and stones are known to have a low water-holding capacity and therefore should be dry.
As a result, the normal moisture meter reading for these materials in between 0.5% and 1%. Higher values could mean a wet or saturated material.
For boundary materials, the values vary depending on the physical properties of what you are testing. As a rule of thumb, you should expect the following ranges for dry materials:
• Mortar: 1% – 4%
• Plaster: 0.5% — 1%
• Concrete: 0.5% — 1%
• Stucco: 0.5% — 2%
Now as we said, in order to inspect a masonry building, you need a moisture meter for every component in the building. That’s quite difficult to have. isn’t it?
So what to do if you can’t find a dedicated moisture meter for bricks, mortar, or stone? The solution is to use a reference scale. More on that in the following paragraph.
Normal moisture reading on a reference scale?
As we have already mentioned on different occasions, all the values that we have discussed so far in this article are for dedicated moisture meters.
This means that when we were talking about the normal readings for drywall, we assumed that your moisture meter was calibrated for drywall and had a specific reading scale for drywall. The same goes for wood, concrete, and plaster.
The truth, however, most moisture meters only have one reading scale that only serves one material (usually wood).
As a result, this scale cannot be used for other materials as it simply won’t make sense.
The solution? We must use a reference scale.
A reference scale is simply a mode in which you can change your moisture meter to allow it to give you estimates of the moisture content in other materials that do not have a dedicated reading scale.
In other words, to check the humidity in drywall using a meter calibrated for wood, you must first switch the instrument to the drywall reference scale.
But be careful here, the values showing on a reference scale do not represent the moisture content of the material under test. Instead, these are just estimates where high values mean high moisture levels and low values mean low moisture levels.
Put differently, if the reference scale shows a reading of 20%, it does not mean that 20% of the dry weight of the tested material is water. Instead, it just means that the moisture content of the material represents 20% of the reference scale.
In general, a reference scale goes from 0 to 100, where 0 is bone dry and 100 is saturated. But there are other moisture meters that have reference scales ranging from 0 to 300.
Ok, what is a normal reading on a reference scale?
The best way to know if the values on a reference scale are normal or not is to compare them to a “normal” sample.
For example, we know that “normal” for drywall is dry. So if you want to use a drywall reference scale, start by applying the moisture meter to drywall that you know for sure is dry. Record the reading you get and use this as a baseline.
Now, during your tests and checks, if the values you get are above the baseline, it probably means there is more moisture than what your sample has.
The baseline value can also be considered as a goal to achieve as you begin to dry out the infected surfaces.
With this in mind, don’t forget to test your MC sample multiple times and from different locations. The humidity percentage changes depending on the surrounding relative humidity. So make sure to check the baseline regularly and verify if it’s still reliable for your tests and checks.
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