Wood Moisture Video Series for Wood Flooring
Wagner Meters and Charlie Phillips from Pittsburg State University are proud to present this Wood Moisture Measurement Webinar Training Series for wood flooring professionals.
This webinar training series provides insight to wood moisture content and the effects it has on products. Wood flooring professionals must have a thorough understanding of the relationship between wood and moisture in order to prevent costly wood flooring installation mistakes.
Defining Wood Moisture Content
It’s universally understood that the success of any wood flooring project depends on taking accurate readings of the wood’s moisture content. Once you correctly measure the wood flooring moisture content, you need to evaluate if it is within the acceptable range before proceeding with wood flooring installation. What is moisture content? It is the weight of the water in a piece of wood versus the oven-dry weight of that piece of wood (or moisture free weight). See the formula below to calculate moisture content:
Incorrect wood moisture content, if left untreated, gives way to a multitude of problems. Moisture content affects wood differently along the grain than across the width because wood does not shrink appreciatively along the grain; that is lengthwise, even with large moisture changes.
Moisture Content Effects on Wood Flooring
The list of problems caused by moisture content is a threat to successful floor installation and longevity. Wood floors will acclimate to the environment in which they are installed. Wood flooring will shrink as it dries and swell as it absorbs the moisture in the surrounding environment.
Shrinking, Swelling, and Moisture Content
If wood flooring has not acclimated to the environment and adjusted to the correct moisture content in which it will be installed, this should be corrected before installation.
Correcting Wood Flooring Moisture Content
There is a close relationship between wood and moisture. Many of the properties of wood flooring are dependent upon its moisture content, and its moisture content levels are dependent upon the environment. It is important to know that kiln-dried wood is not exempt from future moisture level changes.
How Are Wood and Moisture Related?
The next question to be answered is: What affects the time it takes for the final equilibrium value to be reached in wood flooring?
Wood flooring moisture content doesn’t change unless the EMC and the moisture content are not equal. The relationship between EMC and moisture content is one that pursues balance at all times.
The relative humidity of the air surrounding wood flooring determines the moisture content of the wood flooring and the equilibrium with its environment. Wood flooring will lose or gain moisture until it is in equilibrium with the humidity and temperature of the air in its environment. It is worth noting that temperature does not significantly affect the moisture content of the wood flooring, nor does it cause it to shrink or swell significantly.
From the time wood flooring is initially manufactured until the time it is installed in a customer’s home or office, it could encounter many different environments with a variety of moisture levels. How much wood moisture changes before achieving its final moisture content depends on various elements.
Moisture Content Management from the Manufacturer to Installation
When wood flooring is taken indoors, it interacts with the air around it, including the water vapor (humidity) in the air. We know that the wood being used in most offices and homes in North America has an average interior EMC (Equilibrium Moisture Content) of 6% to 9%. As a rule of thumb, wood technologists say that this 6% to 9% EMC comes from a relative humidity of 30% to 50%. Of course, this varies with geographic location; that is, is it a coastal location or an inland location?
The correct moisture content for raw materials coming into a manufacturing facility, as well as for wood flooring during manufacturing, storage and installation, depends on the ultimate in end use EMC for the product.
The typical desired average moisture content for lumber, parts and components intended for interior products, such as a wood floor, is 6% to 7%. This is especially critical for wood flooring professionals who strive for a successful installation and who want to avoid warranty work.
Since wood is a variable material with no two pieces identical, there will always be some small variation in moisture content under 1% in individual pieces exposed to the same EMC. As a general guideline, the ideal difference between the moisture content of wood and the EMC of air is 2% moisture content.
It is also important to achieve moisture content uniformity through kiln-drying and appropriate dry lumber storage in handling, both of which add to the price of wood flooring.
Successful control of moisture content begins with the kiln operation. Then, once the lumber is kiln-dried, the lumber must be stored at the correct EMC to prevent undesired changes in moisture content.
Storing Wood Flooring
When it first arrives, kiln-dried lumber in process parts and manufactured wood components must be stored at the correct EMC to prevent undesirable changes in moisture content.
Because wood components are much smaller than lumber, they have more surface area per volume and the grain is more exposed than lumber; therefore, wood components will change moisture content much faster than lumber if the EMC of the air isn’t equal to the moisture content of the component.
A critical element in controlling moisture content in wood components involves controlling the EMC in the manufacturing facility; you want the EMC to be as close as possible to the EMC in a customer’s home or office. Wood floors that are intended to be installed indoors should never be stored outside or in an unheated building or shed.
Spotting any potential moisture problems and taking the proper steps to avoid them is the key to your success for any wood flooring or woodworking project.
Here at Wagner Meters, we welcome your questions and encourage you to call us at 844-444-9098.