Regardless of how diligently you work to lay a wood floor, your efforts could be fruitless without taking moisture content into consideration. The moisture content of wood can significantly impact machining, gluing, and finishing as well as the product's overall appearance and performance. Because of this, flooring installers and contractors must understand both the basic underlying properties of wood moisture content and how the various types of meters work.
In this article we will explore:
Why testing for moisture content is so important
How a pin-type moisture meter works
Best practices for using a pin-type moisture meter
The purpose of moisture meters for wood
Although the concept of moisture content may sound simple enough, it is quite complex. In a nutshell, moisture content compares the weight of the water contained within a piece of wood against its oven-dry weight. In a perfect world, all moisture content testing would be completed via an "oven test" wherein a piece of wood is weighed before being placed into an oven at 212 degrees Fahrenheit (100 C) for around 24 hours. When the wood ceases to lose weight, it's considered oven-dry and moisture content can be determined. Unfortunately, for professionals working on a job site, this isn't possible. It is for this very reason that devices such as the pin-type moisture meter were developed.
How the pin-type moisture meter works
Pin-type moisture meters function in such a way that the electrical resistance between two electrodes can be measured. When moisture is present within the wood, electricity flows more easily. Conversely, wood that is becoming dryer will resist electrical flow. This resistance is measured in ohms and then converted to a reading expressed as % moisture content. Delmhorst uses the USDA standard - Douglas Fir - as the basis for all calibrations. Readings are obtained by inserting the pins into various depths or areas of the flooring and sub-flooring.
Although a pin-less meter does not require the insertion of pins into the woods (by means of capacitance), the advantage of using pin-type moisture meters with insulated contact pins is that they provide the best means for identifying the precise location of moisture in sub-floors, or in lumber that is being kiln-dried. This is because the pins are only able to read moisture levels at their un-insulated pin tips. By driving the pins into the floor, and even through to the sub-floor to different depths, moisture levels are read each specific penetration level.
Pin-type meters are the only instruments that indicate the moisture conditions inside a board or a piece of wood. Using insulated pins, only the uncoated tips are exposed to the wood fiber, providing more accurate readings of moisture content at various levels of penetration.
A popular pin-type meter among flooring contractors, woodworkers, furniture manufacturers, Quality Control Inspectors and small lumber mills is the Delmhorst J-2000 Pin Type Moisture Meter. The durable digital hand held device helps to keep up with ever-changing job conditions. With built-in wood species correction and temperature correction, the J-2000 is an extremely versatile tool and a great value.
Some conditions such as wood thickness, wood species, and multiple layers are particularly difficult to penetrate with standard contact pins. Using a Slide Hammer Electrode like the one pictured below allows easy pin penetration in hardwood floors.
Best Practices for using a pin-type moisture meter
In order to obtain the most accurate results, here are a few tips and tricks that can simplify the process of using a pin-type moisture meter correctly:
A pin-type uses two pins that penetrate into wood at the user’s desired depth.
Line up the pins with the longitudinal axis of the wood. In layman's terms, the pins should be aligned with the grain as opposed to against it.
Using a pin type meter with insulated pins is the most effective method to determine moisture gradient, which is the difference between shell and core moisture content.
When using non-insulated pins verify that the surface of the wood is dry. If the surface of the lumber is wet, you'll get an erroneously high moisture content readout.
Choose a pin-type moisture meter that features simple controls and a display that is easy-to-read. It's also smart to pick a model that is calibrated to Douglas Fir - the standard species used by the wood science industry.
If you are testing a variety of species, look for a moisture meter that has built-in species corrections to make your job easier such as the Delmhorst J-2000.
To learn more about moisture meters, be sure to contact our moisture meter specialists today.
