The Moisture Measurement Blog

Issue No. 18

AT A GLANCE

*Storing and Acclimateing Your Lumber

* Moisture in Concrete: Free and Bound Moisture

Interesting Websites

Concrete Floors and Moisture

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Scientific article about different methods to measure moisture in concrete. Great information about the different types of water in concrete.

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Storing and Acclimating Your Lumber

Many woodworkers end up collecting and storing all different types of wood whether its leftovers from a previous project, or wood for a project that will be happening down the road. It usually ends up in an old shed or the side of the workshop and of course preferably in a climate controlled room. Wherever you may be storing wood it is important to understand how the climate the wood is in affects the usability of the wood.

If dry wood is stored in a damp place the wood will pick up moisture and expand until equilibrium with the surrounding air has been reached. If the wood is stored in a dry area the wood will lose moisture and shrink until equilibrium has been reached. For corresponding values check the EMC chart.

Proper acclimation of your wood before starting a project will minimize moisture problems when the woodwork is done and brought into the home. Nothing is more frustrating than making a nice dresser and bringing it into the home only to have it shrink and cause loose joints. An easy recommendation that we always provide our customers is to take a moisture meter and measure a table or some other woodwork in the home. Once you have established what the wood has acclimated to in the home then you have a MC% of what you want your wood that you are working with to be.

Moisture in Concrete, Free vs Bound Moisture

Water in concrete is presented in three states: as free water held by capillarity, as absorbed water held by surfaces forces and as bound water held chemically. The ideal method of moisture measurement should quantify amounts of these three states but this is a difficult task because moisture in concrete is not uniformly distributed, and moisture distribution varies with the exposure time (Li Chunqiu 2008). Temperature, wind speed and environmental relative humidity are variables that must be considered at the moment of this measurement as well.

Using a pin moisture meter or a pinless moisture meter Is not a good method for analyzing moisture in a concrete slab. These types of meters are not able to pick up the different types of water in concrete. The meter will measure all of the water in the slab not just the free water.

The free water is what is going to affect the vapor emissions that will cause floor covering failure.

Measuring the moisture of a concrete floor is very hard because of the nature of concrete. The floor covering industry is always evolving and trying to incorporate a more accurate and efficient method for evaluating moisture in a concrete slab. Ten years ago, people were only doing the calcium chloride test when analyzing moisture in concrete. Today many manufactures and people in the floor covering industry have moved to using the RH in-situ probe method following ASTM F2170 standards. Lignomat has developed a system for measuring concrete following the ASTM F2170 guidelines. Please call if you are interested in purchasing. If you would like a more detailed video of how the system works, please visit link below.

https://youtu.be/UnyRz6XFTqs

Li Chunqiu, L. K. ( 2008). “Numerical analysis of moisture influential depht in concrete during drying wetting cycles.” Tshingua Science and Technology Vol 13, N°5: 696-701.