Prevent Cupping in Hardwood Flooring: How to Deal with Excess Moisture

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Have you ever stood on a hardwood floor and noticed that the boards appear wavy and washboard-like? Were the long edges of the boards higher than the centre of the boards, which appeared concave? That’s called hardwood cupping. Excess moisture is the culprit when it comes to hardwood cupping. This happens when the humidity level is high, when the boards absorb too much moisture from the subfloor, from water leaks and spills or even by cleaning your hardwood flooring in the wrong manner. Hardwood cupping can lead to more serious issues such as cracked boards and peeling finish and could eventually cause the flooring to buckle. Let’s take a look at some causes and how they can best be dealt with.

High Relative Humidity

Even the most carefully installed flooring can be subject to hardwood cupping, especially during the humid summer months. If the cupping is throughout your home, humidity is likely the cause. The best prevention is to keep your home’s relative humidity below 50%. Do this by running an air conditioner on hot days, and by turning off your home’s HRV (Heat Recovery Ventilation) system. If the HRV is turned on during the summer, it will continually bring the damp air from outside into your home.

Subfloor Moisture

Another common cause of hardwood cupping is a sub-floor that has higher moisture content than the wood itself. This can happen to hardwood floors installed in a new construction home without heat or air conditioning when the floor is installed. To prevent cupping in this type of situation the wood should contain the same or close to the same moisture content of the sub-floor. This can be done by acclimatizing the home to in-use conditions before and during the flooring installation, and by making sure moisture barriers such as Aquabar underlay are in place. Basement floors also tend to have excess moisture, so choosing the right flooring for that situation can also help prevent hardwood cupping. If you’re planning on installing hardwood in your basement choose the more durable Engineered Hardwood floorings that are designed for use over concrete. To prevent hardwood cupping in a basement situation run a quality dehumidifier that’s large enough to handle the area. Use a unit that drains automatically, set it at 35% and let it run all summer long.

Spills, Leaks and Cleaning Techniques

If the hardwood cupping you’ve noticed is only in certain areas such as near sinks it may have been caused by spills or leaks. Always clean up any water spills immediately and if there is a water leak somewhere, get it repaired before the cupping damage is out of control. Proper cleaning techniques will go a long way to preventing hardwood cupping. Never use an overly wet mop or excessive water to clean your hardwood floor, and never use  a steam cleaner. Instead, go over the flooring when needed with a dust mop. When you need to wash the floor, choose a hardwood floor cleaner with care because many will leave an ugly, sticky film. We recommend using our Gaylord Floor Cleaner which evaporates rather than settling on the floor. Taking steps to prevent hardwood cupping can go a long way to minimizing the problems, so don’t let cupping ruin the appearance of your beautiful hardwood flooring.

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