Buckled hardwood floor

What is Peaking, Buckling, and Cupping in Wood Floors?

Written by: BuildDirect



Time to read 4 min

Wood floors are temperamental under the best of circumstances, which is why you’re strongly advised to hire professionals to install your wood floor unless you have experience with the DIY approach. Both engineered and solid hardwood floors are at risk for issues that change the shape and appearance of the wood. You have to worry about more than water damage as you care for your floors, making it essential to keep an eye out for signs of the most common problems that plague wooden floors, like cupping, buckling and peaking planks.


The Effect of Humidity and Moisture on Wood Floors

Wood floors add a rich elegance to any space, but they’re somewhat delicate and sensitive. Humidity and moisture almost always cause the disfigurement and warping that most often affect hardwood floors. You can’t always control the humidity where you live, and moisture can cause an issue even if you don’t have any problems with leaking pipes or flooding.

The air in any given space has a relative humidity, or RH reading. Unless the RH in your home measures zero or under, then there’s water vapor in the air. Over time, the wood in your home — the walls and doors as well as the floors — becomes accustomed to the humidity level and reaches an equilibrium. You may hear the house settle and the floorboards creak in weather that throws that equilibrium out of whack, but for the most part, the wood finds a happy medium.

Extreme changes in moisture content leads to warped boards. It may take time, but the additional water vapor in the air will ultimately swell the floorboards. In some homes, the wood behaves itself for a year or more, only to suddenly twist out of shape or split. The nature of the moisture in the air results in different types of hardwood damage.

What is Cupping in Wood Floors?

Cupping is a common problem found in hardwood floors. As the name implies, the surfaces of boards that suffer from cupping have a concave shape. They bow inward, resembling the bowl of a spoon — or the inside of a cup. The sides of each board are higher than the middle sections. Solid wood floors and engineered boards can both suffer from cupping, although moisture has a different effect on each type of flooring.

The most distinguishing feature of cupping that sets it apart from other kinds of damage is the location of the moisture damage. Floorboards resemble a sandwich in cross-section. Cupping is the result of an increased moisture content that saturates the bottom of the boards. Set a small piece of paper onto an equally small drop of water and you see the same concave shape.

Noticeable cupping that shows up over the span of a few days is likely because of underlying water damage. It may point to a serious problem, such as leakage. Those are straightforward, making it easier to pinpoint the problem. You know to look for appliance leaks, leaks in the building, site grading issues, or plumbing problems. Floorboards that cup because of too much water vapor in the air will warp more gradually. Those culprits are more difficult to discover since there are no immediate changes.

What Are Buckling Floorboards?

Excessive moisture also creates buckling in solid wood floors, engineered wood, and laminate. Regarding the nature of the damage, buckling is the opposite of cupping.  It bows the other way, forming grooves and peaks. The boards typically lift right off the floor.

High RH can result in buckling, as can moisture located somewhere below the surface of the flooring, such as concrete slabs. Flooding is another culprit, but leaks from above create disfigurement as well. Take heed, however, as improper installation almost guarantees you’ll have a problem later.

What is Peaking Hardwood?

Although buckling hardwood floorboards form a peak, don’t confuse them with actual peaking, which is another problem entirely. Specifically, peaking is an expansion problem. Poor installation is the most common reason that wood flooring peaks.

Wood floors contract and expand depending on the humidity in your home, the temperature, and the weather. Considering this during the installation process is crucial. Whether you do it yourself or hire a professional installer, double-check that space remains between each floorboard. Maintain space between the flooring and the walls, as well. Otherwise, the wood has nowhere to go when it expands. There’s no room to accommodate the swelling, resulting in crested hills.

What Are Crowning Boards ?

Crowning, like buckling and peaking, occurs when a floorboard is higher in the center than it is on the edges. It usually happens after water is left standing on the wood or if the floor’s exposed to high humidity over a long span. Unfortunately, it’s also possible to cause crowning in an attempt to fix cupping.

How to Fix Common Hardwood Plank Issues

To fix floorboard cupping, you can simply sand the floor to make it even. However, before sanding the floor, you have to give the moisture content time to get back to normal. Failure to give the wood time to dry can cause crowning.

In cases where the floorboards heave upward, sanding isn’t recommended. You can, however, try to spot treat the areas that buckle, crown, or peak. Remove the affected hardwood, give the rest time to dry, and then replace the damaged boards. Any time you reinstall pieces of flooring, remember to leave room for the wood to expand. Don’t leave too much, though, or else you’ll have unsightly gaps between the boards.

You don’t necessarily have any control over unexpected moisture issues, such as flooding or leaking pipes, nor can you do anything about humidity or moisture in the air. You can, however, protect your floorboards with a sealant product. Using a dehumidifier in rooms with hardwood flooring during periods of dampness or high humidity is helpful, as well. Even if you do incur moisture damage, there’s no need to replace your entire floor. Although it’s something of a hassle to sand your hardwood or replace individual boards, it’s less expensive and frustrating than ripping up everything.