When looking for warm and natural flooring, wood tops the list. The range of colors, grains and varieties makes it possible to achieve a durable look that harmonizes with any décor or lifestyle.
However, part of what makes wood so appealing, its natural structure and abundant supply, is also what makes it open to some common problems. These problems are all connected to the relationship between wood and moisture.
Hygroscopic: What That Means for Your Floor
Wood is a hygroscopic material, which simply means it easily absorbs moisture.
Woods cells fit together like groups of drinking straws or thin pipes. The cell wall naturally contains a small amount of moisture, and the “hollow” part of the cell also has room to hold and release moisture. While a tree is growing, this cell interior conducts water and nutrients from the roots to the various parts of the tree.
Once a tree has been cut, the “green” lumber is kiln-dried to remove the bulk of that mobile moisture before the lumber is manufactured into various wood products. The structure of the cell remains the same, with room to re-absorb and release moisture from its surroundings. That moisture may come from an external source (like ground water or leaking plumbing) or water in the atmosphere (relative humidity), but it is crucial to note that there is a continuous interaction between wood and its environment.
The catch, for any woodworker or wood flooring expert, is that as this process takes place, the dimensions of the wood will expand or contract depending on how the wood is absorbing or releasing moisture based on the environment around it. When the rate of expansion or contraction changes too drastically, wood flooring will show some tell-tale, and potentially problematic, signs.
5 Moisture-Related Flooring Problems
Cupping is caused by a moisture imbalance through the thickness of the wood, and shows up as a curve from side to side; the edges are higher than the center. It may be a water source from below the flooring, or from ambient relative humidity (RH) changes in the surrounding environment that caused the boards to expand further than the space given them during installation. The resulting pressure would force the board edges upwards, creating a washboard effect.
Crowning is also a result of moisture imbalance, but is the inverse of cupping; the center is higher than the edges. It may result from excess moisture on the face (top) of the flooring, but it may also happen if a cupped floor was sanded and finished before properly reaching a moisture balance with its environment. As moisture leaves the boards, the edges that were sanded down shrink even further, leaving the centers raised.
Some slight spaces between boards are common and are only a seasonal variation as ambient RH changes. However, if the flooring was installed while the moisture content (MC) was still higher than the ambient conditions, the spaces between the boards will grow larger as the boards dry. The wider the board, the wider the gap will become. Large gaps can also be caused by environmental issues such as “hot spots” created by appliances or inadequately insulated heating/cooling ducts that increase the rate of moisture movement in select spots of the floor.
Buckling is really an extreme case of crowning, where extreme moisture changes actually curve the flooring to the extent that it no longer contacts the subfloor. This usually happens most often after a floor has been flooded for a period of time. Incorrect installation may contribute, too, but buckling is extreme enough to generally require correction for the moisture problem and then re-installation.
When a wood floor has been subjected to repeated significant moisture changes, it can result in popped nails, subfloor problems or adhesive breakdown that means the flooring has room to move or rub against the different parts of the floor system. Those squeaks, groans and other noises may be indicative of ongoing moisture related problems.
Minimize Problems with Moisture Measurement
The best single step that you can take to protect a wood floor from these moisture-related problems is to measure both the subfloor and the finished wood flooring’s MC thoroughly and accurately before and during installation, to instruct clients on basic maintenance during the life of the floor, and to educate the client on the natural seasonal changes of a wood floor.
A wood moisture meter can be used to measure and assess the MC of a wood flooring at any stage, from delivery to the job site, through every step of installation, to routine maintenance during use. By understanding the relationship between wood flooring and MC, accurately determining when the floor has reached an equilibrium with its surroundings can let installers minimize the potential problems of excess moisture in the finished floor.
An accurate wood moisture meter represents the ounce of proverbial prevention for a pound of possible problems for any wood floor.