Hardwood Floor Problems: Heed the Warning Signs

The moisture content (MC) of wood, must be managed to achieve optimum beauty and durability. When relative humidity (RH) rises, wood absorbs moisture from the air. When RH falls, wood loses moisture to the air. This is a completely natural process, but excessive MC changes can cause wood floor water damage.

Wood Floor Problems Caused by Excessive Moisture

Most problems with wood floors are caused by too much moisture. These are some of the most common causes:

Caution: Wet Floor

  • Water on or under the floor
  • High humidity
  • Improper or no acclimation
  • Poor installation

Water on or Under the Floor

Any moisture that comes from below a subfloor or gets between the subfloor and the flooring can cause problems over time. Leaking appliances, groundwater intrusion through a perforated vapor barrier, condensation, and even moisture from a concrete subfloor that had not completely dried can introduce moisture to your flooring. It might be the terrain of the site with rain and runoff not moving away from the foundation that can cause moisture-related problems with the wood flooring over time. Recent flooding or even spills that aren’t quickly and completely cleaned up could also be a problem.

High Humidity

If you live in an area with humid weather, the floor can absorb moisture from the air during humid months. This will cause the wood to expand and can cause problems.

Improper or No Acclimation

Before a wood floor is installed, the wood must be “acclimated” to the average temperature and humidity of the space where it will be installed. This means it must be stored in an area with similar conditions and allowed to either absorb or lose moisture to the surrounding air until it stabilizes. Once it stabilizes, it won’t expand or contract as long as the surrounding conditions remain constant. If the floor isn’t properly acclimated before it’s installed, it will expand or contract after installation and cause problems.

Poor Installation

There are several ways a poor installation can cause flooring problems. Some mistakes will not allow the floor to move as it absorbs moisture. For example, the planks might have been installed with the wrong size fasteners or not enough fasteners. For instance, there might not be adequate expansion gaps around the perimeter of the floor. For large expanses of floor, there might not be adequate expansion joints. This can cause buckling in the floor.

Other installation mistakes can allow the floor to absorb too much moisture. The subfloor might have been too wet when the floor was installed over it. If the subfloor is concrete, it might not have a vapor barrier installed underneath. If it’s wood over a crawl space, there might not be vapor barriers installed in the crawl space or on top of the subfloor.

Common Hardwood Floor Problems and Visible Signs

Some moisture-related problems are visible to the discerning eye. Primarily, wood flooring problems can occur when the wood expands and contracts. This “wood movement” occurs naturally according to seasonal shifts or when ambient RH levels change in the home. These changes can also present a less-than-desirable change in the appearance of your wood flooring.

Wood Floor Problem

Cracks and Separations between Boards

When homes are heated in the winter, RH levels can plummet, boards can shrink, and spaces appear between the boards as the wood loses MC. Some of these variations are seasonal problems and will close up on their own when the weather (and related RH) changes and the MC of the air increases. Monitoring the room’s temperature and RH level, then taking corrective action, can also minimize seasonal shifts in the wood floor. As an example, homeowners can add moisture to the air during dry winter months by installing a humidifier in the furnace.

hardwood floor cupping related problems

Cupping

Cupping is when the edges of a board are higher than its center due to moisture, which causes the wood to expand. This can occur after water spills onto the floor and is absorbed by the wood. However, usually high RH is the culprit. As the wood expands, compression can result as the boards are crushed together, deforming the boards at the edges. Cupping is caused by a moisture imbalance through the thickness of the wood. The wood is wetter on the bottom of the board than on the top surface, which dries quicker than the bottom. Cupping most often appears after the floor has been installed and in some cases, the floor will cup even if it was installed correctly. Can wood floor cupping be fixed? Learn if cupping can be fixed or not.

Crowning

The opposite of cupping, crowning occurs when a board’s center is higher than its edges. A common cause is moisture exposure or imbalance. If the surface of the floor is left exposed to water or left in humid conditions for an extended period of time, the moisture can saturate the wood flooring and cause crowning. Another cause is that the floor was previously cupping, but was sanded before the MC returned back to its normal state. In this case, the floor should be given time to dry before sanding. The sanding process can cause the raised edges of the board to flatten while lifting up the middle of the board if the floor is sanded while the boards remain cupped and moisture is still present.

hardwood floor buckling problems

Buckling

Floor buckling is the most extreme reaction to moisture in a hardwood floor. Buckling occurs when the wood flooring actually pulls up from the subfloor, lifting several inches in one or more places. Fortunately, this is not a common occurrence. Floor buckling happens most often after a floor has been flooded for an extended period of time. If caught early, spot repair and replacement may be possible. Once the standing water is removed, several boards can be taken up from the floor so that the air can circulate across and below the floor. When the floor has dried to a more stable moisture level, hardwood floor repairs can usually be made.

Don’t let these moisture issues happen to your hardwood floors. Use an Orion wood moisture meter to save time and money.

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How to Prevent Hardwood Floor Buckling and Cupping
5 Tips

1. Acclimate the Flooring

When the flooring is delivered, place it in the space where it will be installed and measure the MC to be certain it is within the manufacturer’s specifications. If it isn’t, allow it to acclimate for the specified time and measure again until it is within spec.

2. Cover the Subfloor with a Moisture Retarder

If this is a nail-down over a wood subfloor installation, lay down a moisture retarder over the subfloor before installing the wood flooring.

3. Provide an Extra Moisture Retarder

If the installation is over a crawl space, make sure there’s a moisture retarder in the crawl space and install an extra one if the existing one is in poor condition.

4. Use the Recommended Fasteners

Use the recommended number and type of fasteners when installing the planks to a wood subfloor. Inadequate fasteners will allow the floor to move too much. However, don’t over-fasten or use fasteners that are too large, or you might crack the planks.

5. Check the Moisture Condition of Subfloors

Determining the MC in a wood subfloor is an essential part of quality control within the flooring installation process. Flooring installers must know the MC of the subfloor as well as of the wood flooring. Test for moisture at several locations in the room – a minimum of 20 per 1,000 square feet – and average the results. You should make sure to measure all exterior and plumbing walls. In most regions, a dry subfloor that is ready to work has an MC of 12% or less. If you record high MC readings, do not proceed with the installation until the origin of the moisture is identified and all moisture-related problems are remedied.

A wood moisture meter is essential for this job. Pinless moisture meters for wood can measure the MC below the wood surface without doing any damage to the wood flooring. Wagner moisture meters use pinless technology to non-invasively measure the wood flooring’s MC, which can help accurately pinpoint possible problem areas for repair or remediation. The newest line of Wagner moisture meters, Orion®, can measure hardwoods, softwoods, and exotic wood species. When MC management makes all the difference, using an Orion wood moisture meter is an invaluable way to effectively resolve the warning signs on wood floors.

All types of flooring are susceptible to failure if moisture conditions are not properly monitored and maintained. When the subfloor is concrete, a moisture problem may begin long before the flooring is installed. If the slab has not been properly dried, moisture problems are almost guaranteed with wood flooring applications. Accurate moisture testing is critical for any concrete slab.

The scientifically proven most accurate test for moisture in a concrete slab is the RH test using in situ probes. This test is the basis for the ASTM F2170 standard. The Rapid RH® L6 system is the fastest, easiest way to test concrete moisture in compliance with ASTM F2170.

How to Care for Hardwood Floors to Avoid Cupping and Buckling

The most important thing to remember about caring for your wood floor is to keep moisture away from it. Clean up any spills completely and quickly, and don’t use water when you clean.

Dust and sweep your floors daily. Vacuum and mop with a spray hardwood floor cleaner weekly. Set your vacuum on the hard floors setting so the wheels and beater bar don’t touch the floor.

Ways to Fix Minor Moisture-Related Problems

Wood floor buckling can sometimes be solved simply by adding weight to the floor until the extra moisture dries out and the planks level out.

If the problem is more serious, then it’s probably because of an excessive amount of moisture from flooding or a plumbing leak. In that case, you’ll first need to fix the problem, then pull up some planks to allow air to circulate and dry out the moisture. Once the floor is dry, assess the wood floor water damage to see if you need to replace any planks.

If moisture isn’t the problem, it could be an installation problem that will involve a call to the installer.

3 Invisible Moisture Problems

Some moisture dynamics can occur beneath a flooring substrate with equally devastating possible consequences for wood flooring applications.

1. Wood Subfloors

Determining MC is an essential part of quality control within the flooring installation process. Flooring installers must know the MC of the subfloor as well as of the wood flooring. Test for moisture at several locations in the room- a minimum of 20 per 1,000 square feet- and average the results. You should make sure to measure all exterior and plumbing walls. In most regions, a dry subfloor that is ready to work has an MC of 12% or less. If you record high MC readings, do not proceed with the installation until the origin of the moisture is identified and all moisture-related problems are remedied.

2. Concrete Subfloors

All types of flooring are susceptible to failure if moisture conditions are not properly monitored and maintained. When the subfloor is concrete, a moisture problem may begin long before the flooring is installed. If the slab has not been properly dried, moisture problems are almost guaranteed with wood flooring applications. Accurate moisture testing is critical for any concrete slab. ASTM International has provided several standards for testing moisture with two different test methods before installing flooring over a concrete slab: in situ probes per ASTM F2170 and calcium chloride testing per ASTM F1869. The best indicator is RH testing using in situ probes per ASTM F2170.

3. Leaks or Water Intrusion

Any moisture that comes from below a subfloor or gets between the subfloor and the flooring can cause problems over time. Leaking appliances, groundwater intrusion through a perforated vapor barrier, condensation, and even moisture from a concrete subfloor that had not completely dried can introduce moisture to your flooring equation. Also from the outdoors, it might be the terrain of the home’s lot with rain and runoff not moving away from the foundation that can cause moisture-related problems with the wood flooring over time.


Free Download – 4 Reasons Your Hardwood Flooring Failed

The Antidote

The best cure is to accurately measure and assess the moisture in the subfloors previous to wood flooring installation and also measure the MC of the wood flooring before, during, and after the flooring installation.

A wood moisture meter helps wood flooring lovers to navigate naturally-occurring seasonal MC changes on a regular basis. Pinless moisture meters for wood can measure the MC below the wood surface without doing any damage to the wood flooring. Wagner Meters uses pin-less technology to non-invasively measure the wood flooring’s MC, which can help accurately pinpoint possible problem areas for repair or remediation. Wagner Meters manufacture moisture meters for wood that can measure hardwoods, softwoods, and exotic wood species, and also manufactures specialty meters for wood finish applications. Wagner Meters also manufactures RH in situ probes for testing concrete slab subfloors.

When MC management makes all the difference, using a Wagner Meters wood moisture meter is an invaluable way to effectively resolve the warning signs on wood floors.

A Couple of Common Questions

What causes wood floors to buckle?

Floor buckling is the most extreme reaction to moisture in a hardwood floor. Buckling occurs when the wood flooring actually pulls up from the subfloor, lifting several inches in one or more places. Fortunately, this is not a common occurrence. Floor buckling happens most often after a floor has been flooded for an extended period of time.

What causes wood floors to cup?

This is when the edges of a board are higher than its center, due to moisture which causes the wood to expand. This can occur after water spills onto the floor and is absorbed by the wood. However, usually high RH is the culprit. As the wood expands, compression can result as the boards are crushed together, deforming the boards at the edges. Cupping is caused by a moisture imbalance through the thickness of the wood. The wood is wetter on the bottom of the board than on the top surface, which dries quicker than the bottom.

Last updated on July 21st, 2021

159 Comments

  1. Heather Ritchie says:

    I want more than anything a 10″ wide custom solid hardwood floor, but am discouraged about what I am hearing from my contractor regarding gapping caused by humidity contraction. He’s saying that I could see as much as a 1/4″ occurrence. Is it possible to alleviate that potential with a moisture barrier and/or can you help with any other solutions to my dilemma? how well would a dehumidifier work? I do not want engineered or laminate flooring.

  2. Loft and Insulation says:

    Wow. This is impressive. Thank you.

  3. ridebiler says:

    Loving the information on this site, you have done great job on the content.

  4. Joanne says:

    I have timber floor boards that have a Gemini finish. For 15 years they have been great. We have resealed with this type of finish a few times over the years in the high traffic areas. In the last 6 months ( no reseal has been done for over a year) the dining chairs have been leaving circle marks on the floor where the leg sits. Every time we move the chairs, sit and reput back under the table a new mark appears. I changed the protectors underneath each leg as I thought they were worn but now have more marks. I’m so disappointed as our floors are our pride and joy. Any advice would be appreciated. Thank you

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