Cupping Deformation on Engineered Flooring

1. What is cupping?

Cupping in engineered flooring is a kind of deformation that flooring warps in a concave shape with pronounced raised edges, or in a convex shape with raised middle. It is caused by changes in moisture levels, whether decreases in the air relative humidity above or increases in moisture from below. Whatever the cause, a moisture imbalance develops from the bottom of the floor to the top.

Cupping in engineered flooring not only disrupts its flatness but can also cause issues such as failure and detachment of T&G joints, wearing out of the surface, and delamination.

2. What causes cupping?

In short, moisture. Wood will balance (equilibrate) their moisture content (MC) with their surroundings. if the air is humid, the wood will absorb more moisture from the air, and it will swell. If the air is dry, wood fibers will release some of its moisture back into the air and it can shrink back down.

It’s common for moisture to enter the flooring boards from below through the subfloor or concrete below, even they are flawlessly-installed. This is why the bottom of the board swells and makes the edges curve upward into an almost wave-like pattern. However, several common situations that are known to cause cupping can be addressed and can even be reversed.

2.1 Change in the relative humidity in the air

Wood flooring can react to the changing amount of humidity in the air. It expands during one humid summers and contracts in the dry winters.

If the cupping occurs uniformly throughout your house and isn’t severe, this is probably the cause.

2.2 Subfloor moisture

Excess moisture in the concrete slab, crawl space, or basement beneath your wood floor can lead to cupping. This issue is particularly common in new constructions where the floor is installed before the HVAC system is operational. It can also occur later if your basement or crawl space consistently retains high humidity.

2.3 Leaks or spills

Cupping caused by leaks typically occurs in areas around sinks, dishwashers, and similar fixtures. If a leak is slow or minor, the cupping may develop gradually, making it hard to notice until it becomes more severe. Sudden leaks or spills can also cause cupping if they aren’t cleaned up promptly or thoroughly, leaving moisture behind.

2.4 Improper care/cleaning

Similarly, when cleaning up significant leaks or spills, cupping can occur if any moisture is left behind. Additionally, if proper cleaning techniques and supplies aren’t used, further damage could result.

2.5 Improper installation

If engineered flooring is installed before the floorboards have reached their equilibrium moisture content (EMC), there is a risk of cupping later on. The moisture content gradient between the floor and the EMC, along with fluctuations in indoor relative humidity, can also cause cupping. To prevent this, it’s essential to ensure that the moisture of flooring has reached the proper EMC for long-term stability.

3. How to fix?

3.1 Determine where the moisture is coming from.

First, determine whether the cupping is uniform or seasonal and if it’s concentrated in a specific area. Additionally, consider whether the floor was recently installed or if there might be excess moisture beneath the flooring compared to the living space.

3.2 Get a dehumidifier

If you live in a region with humid summers, or the basement tends to be more humid than others rooms, you may need to run a dehumidifier seasonally to keep your wood floors in top condition throughout the year. The key is to control the indoor climate and maintain consistent conditions as much as possible.

3.3 Maintain your floor properly

Using the correct cleaning methods and products made specifically for wood floors. Always dry spills thoroughly, and routinely check wood floor areas around sinks, dishwashers, bathtubs, and other areas more likely to have leaks or spills.

3.4 After a significant leak or spill

If water have soaked into the floor, it might be necessary to call professionals who have high-powered drying equipment. While a dehumidifier can handle air humidity, wet and warped floors require a more targeted and intensive method to prevent long-term damage.