top of page
  • Writer's pictureFloors Depot Team

Moisture Under Hardwood Floors – How It Happens and What to Do About It

Moisture Under Hardwood Floors

Hardwood is a beautiful and long-lasting flooring material. While hardwood floors can last for decades or even lifetimes, they require proper care and attention to remain at their best, almost like a living thing. As far as floor care is concerned, one of the most important pieces is protecting your floor from moisture.

In a living tree, the role of the tree’s trunk is to facilitate passing nutrients from the roots to the leaves and branches, and vice versa. This fact means that wood naturally has a high affinity for water and draws in moisture easily when dry. The problem is that moisture will cause your wood to swell and expand. The pieces will get longer along the direction of the grain, and shorter across it. The effect is unpredictable, which warps your boards and causes your floor to buckle. This isn’t even getting to the other damage moisture can cause, such as rot, and mould.

How Do Moisture Problems Happen?

There are a variety of ways your engineered hardwood flooring could be exposed to a problematic level of moisture. It could happen suddenly, as with an accident, spill, or mild flooding. However, these sources of moisture are more obvious and will not usually happen without your knowledge. There are other ways that moisture can affect your floor that is more dangerous and harder to detect.

While these problems ideally should have been identified prior to installation, hardwood floors can also be damaged by condensation, groundwater intrusion, or excess moisture from a concrete subfloor. Any of these can introduce enough moisture to seriously damage your floor.

Lastly, ambient humidity is also a concern. Most of us are aware that temperature causes wood to expand and contract, and that it’s normal to have some changes throughout the seasons and even throughout the day. Humidity also has a profound effect on your wood, with relative humidity in your home of 30% to 50% being advisable to preserve the best health of your floors. As the humidity increases above 50%, your wood will begin to absorb humidity from the air.

Signs of Moisture Problems

It’s important to know the most common signs of moisture problems so that you can correct any damage as soon as possible and prevent further deterioration of your floor.

The most common sign that humidity is affecting your floor is the appearance of cracks or gaps. When these start to show up on your formerly neat floor, it’s a sign that some of the boards have begun to expand or contract with variations in humidity. Excess humidity usually leads to cracking as boards push against one another. If you’re seeing cracks, it’s good to start evaluating the effects that moisture might be having on your wood floor.

Warping is the next more common sign, and it’s a big red flag! A board can either cup, where the edges bend up higher than the center, or crown, where the opposite occurs. If you catch the problem before it gets worse, it’s often possible to reverse the warping if you can remove the source of the excess humidity. Cupping and crowning are both very bad signs!

Lastly, the worst sign of moisture damage is extreme warping or buckling of your floor, where one or more of your floorboards begin to lift off from the subfloor by several inches. Luckily this only happens with extreme moisture exposure, as your damaged floor will need to be entirely replaced in the event of buckling.

How to Remove Moisture From the floor?

If you’ve noticed telltale signs of excess moisture, it’s a good idea to invest in a wood moisture meter. This device can be used to determine the moisture reading of any of your wood planks within just a couple of seconds. Not only can a meter help you locate the source of the problem, but will also let you confirm that you’ve solved it.

If you’ve got a serious moisture problem, like a large spill, leak, or even mild flooding, it’s imperative that you act quickly to prevent damage. Once you’ve removed the source of the water on your floor, immediately dry all visible water as soon as possible. A mop and towels will be sufficient for smaller amounts of water, but for larger emergencies, it’s a good idea to invest in a water pump as soon as possible. Be sure to remove any objects on your floor that have become waterlogged, such as carpets, mats, or clothing.

Once you’ve stopped the inflow of new water and visibly dried your floor, you’ll need to help your hardwood give up any water that has already entered the planks. To do this, use fans to move air from wet to drier areas of your home, and bring in dehumidifiers to remove moisture from the air. In a serious situation, you’ll need a commercial dehumidifier to control the moisture levels before they cause real damage.

If your wood moisture problems are chronic, instead of being due to a spill or leak, you’ll need to resolve whatever is causing the humidity in your home to be elevated. If the main cause is high environmental humidity, you’ll need to control it to avoid damage over time. Using dehumidifiers and utilizing central air with the door and windows closed in times of high humidity is a good strategy to keep your wood safe.

Besides a careful hardwood flooring installation, the best way to keep your wood safe is to keep up with regular maintenance. Ensuring that your floor has been regularly treated and the finish is in good shape is the best way to guard against moisture.


Think of moisture as the natural enemy of your hardwood flooring. To protect your investment, you need to keep your home free of excess moisture. Act promptly in the event of spills and leaks to avoid catastrophic damage, and keep an eye on the humidity level, which can slowly warp and bend your wood.

Investing in a wood moisture meter can give you immediate feedback on how well you’re doing at keeping your wood in top shape. Lastly, while the best defence you can give your wood is preventing contact with water in the first place, the second best is to make sure your wood is regularly screened and recoated to keep its finish in top condition–usually once every three years.

bottom of page