You’ve had a beautiful hardwood floor installed in your home. But after a while, something doesn’t look right—or feel right. Maybe the floor seems “wavy” or even rippled. There may be raised, small ridges at the edges of certain planks. 
What’s happening to your previously gorgeous flooring? Can it be stopped?
Cupping It is one of many problems that hardwood floors may encounter. It can happen to most types of wood, and it’s often the first observable sign your floor is being affected by moisture.
Since wood reacts to moisture so easily, floorboards can warp as they react to the change in their internal moisture content (MC) after the floor’s installation. If you can catch the problem early, your floor will be back to normal.
Here’s what you need to know.
How to fix hardwood floor cupping
- Make sure you have a reliable wood moisture meter so you know how much the wood moisture content has risen or can identify wet problem areas. There are many types of meters, but few that allow you to test multiple areas at once without damaging the wood. The Wagner Meters Orion® moisture meter line uses electromagnetic wave frequency (EMF) to measure large areas.
- Find out where the moisture is coming. Is the cupping seasonal and uniform, as previously mentioned? Are the cuppings restricted to a single area? Are you unsure if the floor was installed recently?
- Get a dehumidifier, especially if you have a basement or an area of the house that tends to be more humid than other areas. You may only need to run the dehumidifier once a year if you live in an area with humid summers. It is important to control the temperature in your home and keep it as consistent as you can.
- Maintain your floor properly, using the right cleaning methods and products made specifically for wood floors. Clean up any spillages immediately and regularly inspect the wood floor around sinks and dishwashers.
- After a significant leak or spill, especially if water or other liquids have had time to absorb into the floor and subfloor, you may need to contact the professionals for high-powered drying equipment. Although a dehumidifier works well for controlling humidity in the air and preventing damage to wet floors, it can cause lasting damage to your floor.
How does cupping work on hardwood floors?
The boards on the floor that are closest to moisture will expand when moisture comes in contact with them. The expansion can take the form of crowning (the center is higher than the edges) and cupping (the board’s center is lower than its edges). Both are due to moisture imbalance in boards.
When light shines through a window onto a wood floor, it can sometimes be easy to see the beginning stages of cupping. It is possible to see tiny shadows at the edges of the floorboards that are slightly higher than in the middle.
How does cupping occur?
In short, moisture. Wood, even when it’s treated and sealed, is still a porous, fibrous material. It can react to the moisture content (MC), in the air around. Wood, for example, will equalize (or balance) its MC with the surrounding environment. This is similar to the principle osmosis.
If the air is dry, wood will absorb more moisture and swell. Dry air will cause wood fibers to release moisture into the air, which can cause it to shrink.
It’s most common for moisture to enter the floorboards from below, through the subfloor. The bottom of the board expands, causing the edges to curve upwards into a wave-like shape.
Cupping Cupping can occur even with a perfectly-installed wood flooring, depending on the environmental conditions and the building. Cupping can be prevented by addressing several common issues.
A wood moisture meter is an accurate tool to detect moisture problems in hardwood flooring and prevent cupping.
Buy an Orion Meter
What are the common causes of cupping in flooring?
- Change in the amount of moisture in the air (relative humidity). Your wood floor may react to changing humidity levels if it is located in an area that experiences dry winters or humid summers. Wood floors expand and contract in each season. Cupping may occur in a fairly uniform manner throughout your house. The degree of cupping should not be too drastic.
- Subfloor moisture. Cupping can occur if there is too much moisture in your concrete slab, crawlspace, basement, or below-floor wood floor. This can happen especially in new construction, especially if the floor was installed before any HVAC system is connected to your home. This can also happen if the humidity is higher in your crawl space or basement.
- Leaks and spills. Cupping Leakage usually occurs around sinks and dishwashers. Cupping can happen slowly or gradually if the leak is not noticed until it gets worse. Sudden leaks or spills can cause cupping if they aren’t cleaned up quickly or thoroughly, or some moisture is left behind.
- Improper care/cleaning. Cupping can also occur if moisture is not removed after cleaning up larger spillages or leaks. What’s more, unless proper cleaning techniques and supplies are used, further damage could result as well.
- Improper installation. If a hardwood floor is installed before a subfloor is properly dried, or before the floorboards reach an equilibrium moisture content (EMC), such as before the inside of a building’s air is conditioned, there is a chance for cupping later on. The area will become more humid and warmer as furniture and people move in. For the long-term, you want to make sure that the moisture levels between the subfloor floor and the finished floor are at the right EMC. You will need the most precise moisture measurement tools to ensure that your moisture readings are accurate for starting the installation.
Is it possible to fix a cupping problem in a hardwood floor that is already installed? Can it be fixed?
In many cases, if cupping isn’t severe, the issue can be fixed once the moisture issue is fixed. Since the process of cupping is the wood reacting to moisture, if the wood’s moisture level returns to the proper equilibrium, the cupping can resolve.
It will depend on the type and extent of the moisture problem.
What happens if cupping doesn’t get fixed?
The floor may also be damaged by visible warping. Cupping can cause gaps between the boards and could worsen. The boards can become brittle or crack if the relative humidity drops.
The main issue is moisture. If the cupping in the floorboards doesn’t go away, it could mean that the underlying moisture issue was not properly addressed and still needs some attention. Cupping may persist after flooding or other severe events, but persistent cupping should be investigated. It is important to avoid prolonged moisture problems as they can cause many flooring failures.
You should not do this if your floor is showing signs of cupping.
One rookie mistake is to simply sand the floor down until it’s level again. Once again, the moisture issue that caused the cupping is not being addressed. If the cupping was caused by humidity, such as from a particularly wet summer, and you sanded the area that is affected, the wood may warp when the air drys out, leading to crowning.
You also don’t want to assume your floor has already failed. There is still hope. You can fix many moisture issues by controlling your home’s climate and taking moisture readings throughout your house. Also, you can find hidden leaks or areas where moisture might be creeping in from other locations.
To avoid these mistakes, there is a way to test for a change in your home’s ambient conditions over time. Relative humidity data loggers allow you to see how your ambient moisture levels have changed over time and how long. This data can be used to help you decide what steps to take regarding your flooring.
Once cupping has been discovered, you must immediately take action.
Cupping can be a sign that your hardwood floors are susceptible to moisture problems. Even before you call a professional, if you have a reliable wood moisture meter you can use to take multiple readings throughout your home, you’ll have a much better idea of what kind of situation you have on your hands.
You might be able to figure out how to remedy the situation yourself if you find it’s due to humidity in the air or a leak or spill. And if you do discover it’s a serious issue, you’ll have much more precise information to give the professionals so they don’t have to spend as much time (and your money) doing detective work.
Protect your hardwood floors with reliable moisture measurement. Learn more about how Wagner Meters’ Orion® moisture meter line is easy to use while providing the most accurate readings available on the market.
A wood moisture meter accurately measures the moisture content of hardwood floors to prevent any moisture issues.
Buy an Orion Meter
Last updated on August 31st, 2021
