Your hardwood floor may easily be one of the most attractive features in your home. Wood floors provide elements of warmth, beauty, durability, and functionality that perhaps no other type of flooring material can match.
An Important Caveat That Requires Your Attention
Yet along with all these wonderful benefits comes one important caveat: you must pay close attention to moisture, or you may end up paying for what could turn out to be an extremely costly headache. The fact is: unchecked moisture can wreak havoc on any hardwood floor.
The issues stemming from excessive moisture can range from buckling to cupping, crowning, gaps between floorboards, and more.
But exactly how do such problems develop? And what should be done to prevent moisture issues? Read on to learn the answers to these important questions.
Common Hardwood Flooring Problems
Before looking at some common flooring problems, consider why wood is susceptible to moisture damage. Wood is hygroscopic, meaning that it absorbs or releases moisture in response to the moisture in the surrounding environment.
When wood absorbs moisture, it expands. When wood releases moisture, it shrinks. This action of expanding and shrinking can lead to significant damage to a hardwood floor—or really any wood floor for that matter.
Wood floor buckling occurs when the wood floor pulls up from the subfloor. The buckled hardwood floor can lift as much as several inches. This is an extreme reaction to moisture in the flooring and happens most often when the floor has experienced flooding for an extended period.
If you catch the problem early, spot repair and replacement may be possible. This requires removal of the standing water and then taking up several floorboards so that air can circulate across and below the floor. When the floor has dried to a stable moisture level, you can usually perform a satisfactory repair of the issue.
Hardwood floor cupping is a common issue that’s seen when the edges of a floorboard are higher than the center. This can occur when the bottom of the wood is exposed to moisture and expands, leading to deformities at the edges of each board.
A key factor in cupping is a moisture imbalance in which the wood is wetter on the bottom of the board than at the top surface. This can happen when the subfloor is too wet or when the surface dries out more quickly than the bottom after exposure to moisture.
Although cupped floors won’t typically occur until some amount of time has passed after the floor has been installed, it can happen even if the flooring was installed correctly. Fortunately, cupping is often reversible by addressing the source of the problem.
Wood floor crowning is the opposite of cupping. It occurs when a floorboard’s center is higher than its edges. But just like cupping, the cause is either moisture exposure or a moisture content imbalance within the floorboards.
If the surface of the floor is exposed to water or a high humidity environment for an extended period, the moisture can saturate the wood and lead to crowning.
Another contributing factor could be a floor that was cupping and then got sanded before the moisture content of the wood returned to normal. In this case, too much sanding along the edges of the boards can lead to a crowning effect. You can avoid this by simply allowing the floor to dry sufficiently before sanding.
Gaps or separations between floorboards can be a common issue when a home experiences wide relative humidity swings between summer and winter. Heating a home during the winter season can cause relative humidity (RH) levels to go down significantly. This low humidity environment will cause boards to shrink as the wood releases moisture into the air.
Especially in the case of a hardwood floor composed of wider planks (4 inches or more) where this shrinkage can be substantial, you may find noticeable gaps between boards when the RH levels go down. However, these gaps will often close on their own when the RH of the air increases during the other seasons of the year.
Monitoring a room’s temperature and RH levels and taking appropriate steps to prevent wide swings in the RH of the air can help to minimize these naturally occurring seasonal shifts in the wood floor. One very easy step is to use a room humidifier during the winter season.
How to Prevent Hardwood Flooring Problems
Serious problems related to moisture are usually preventable if you know what actions to take. Here we provide four critically important actions that should never be overlooked when getting ready to install a hardwood floor.
1. Measure Moisture Content
Your first and most obvious strategy for preventing problems is simply to measure your hardwood’s moisture content. And this should start at the beginning, when the wood first arrives at the installation site. You’ll want to take numerous measurements because not all boards will have the same moisture content.
The target wood moisture level will vary depending on the climate at your geographic location. But typically, you want the moisture content to be 6-9%. Although, in some areas the target moisture content may be between 8 to 12%. Do a quick internet search to find the target moisture content for your area.
Obviously, you won’t know when the wood has reached the correct target range for moisture unless you measure its moisture content. But this is no big deal because you can take measurements quickly and easily with a handheld moisture meter. We’ll discuss meters in a bit more detail later.
2. Acclimate Wood Flooring Before Installation
What happens if you measure the wood’s moisture content when it’s delivered to your installation site, and you learn that the wood is not even close to the target moisture level? Send it back. Many people assume you can acclimate wood that’s too wet, but unfortunately, it just doesn’t change enough to make a difference in a reasonable amount of time, unless it’s already right on the edge and you have a couple weeks to spare. That being said, wood flooring associations still recommend you acclimate wood (that is already at the correct moisture level) to minimize the chance of problems.
To allow for acclimation, you always want the wood delivered a minimum of 3 days before the scheduled installation, preferably longer. But don’t be surprised if your hardwood needs more time than that. If wood is stored in a higher humidity environment before delivery—even just for a short period of time—it’s possible that the wood may take a significant amount of time to acclimate properly. Wood moisture doesn’t change quickly in a normal environment.
You must make sure the room is at service conditions (i.e., heating system turned on during the cooler months, and doors and windows closed). Without that, the wood moisture content is probably moving in the opposite direction of what you need.
3. Check Subfloor Conditions
The moisture condition of the subfloor is another factor that you must consider if you are to prevent flooring problems from occurring after the floor is installed. It does not matter if the subfloor is plywood, OSB, concrete, or some other material.
The rule of thumb is that you will want your hardwood boards and your subfloor to be within about 2 percent moisture content of one another. So, for example, if your hardwood boards are at 8 percent moisture content, then your subfloor should be somewhere between 6 to 10 percent moisture content at the time of the floor installation.
In the case of a concrete subfloor, the most reliable method of measuring the concrete’s moisture condition is to use an in-situ RH test kit. You could also opt for the convenience of a handheld meter that is specially calibrated for concrete, but just be aware that your results won’t be as reliable as what you’ll get with the in-situ RH test.
4. Use a Moisture Meter
A wood moisture meter makes it quite easy to take lots of measurements of your hardwood’s moisture content. However, not just any moisture meter will do. You have a choice between a pin-style meter or a pinless meter.
You want to use a pinless moisture meter. A non-damaging pinless meter won’t leave unsightly pinholes in your hardwood flooring, plus it is extremely fast, making it easy to get a lot of measurements in a short amount of time. With a pin meter, each measurement can seem to take forever because inserting the pins into dense hardwood can be laborious and difficult to do correctly.
You also want to use a high-quality meter that’s engineered for accuracy and reliability. You can take all the moisture measurements in the world, but if you’re using an inexpensive meter that gives inaccurate readings, it won’t do you any good.
Even worse, inexpensive meters typically do not feature a way to check the calibration of the meter. Your meter could be out of calibration, and you wouldn’t even know it. You certainly don’t want a meter like that!
Another thing to be aware of with wood moisture meters is that you want to pay attention to species settings. If you are installing red oak flooring for example, you must adjust the meter’s species function to red oak to ensure accurate readings.
Discoloration: A Warning Sign of a Moisture Problem
Most any hardwood will exhibit color variation that’s completely natural and expected. For example, hickory planks will show a distinctive color pattern ranging from creamy-white sapwood to dark, brown heartwood. Color patterns like these can be desirable, especially when seeking a rustic, less formal look.
But sometimes, wood gets discolored in a way that’s not natural or desirable at all. In these cases, the discoloration likely stems from excess moisture. Dark staining in the wood could indicate the growth of mold or mildew. In the case of mold, the spores can cause unwanted staining of your wood floor.
If you notice staining or discoloration that you did not expect, your first course of action is to investigate for moisture using your wood moisture meter. If you find excessive amounts of moisture in your floorboards, your next step is to determine where that moisture is coming from—assuming your floor was installed correctly and the wood was fully acclimated to the proper moisture content.
Your Key to a Long-Lasting Hardwood Floor
Few aspects of your home bring more satisfaction and enjoyment than a properly installed and maintained hardwood floor. But remember the caveat about moisture in wood and take the smart steps for preventing moisture damage that we’ve highlighted here.
For more information about high-quality wood moisture meters, check out the top picks in moisture meters, based on the comprehensive laboratory testing by Moisture Meter Experts.