How To Fix Warped Wood Floor

An image of a warped wood floor

While wood floors have a reputation for durability, they are highly susceptible to water damage if not appropriately maintained. This water damage usually manifests as warped floorboards that are unappealing and structurally insecure. Fortunately, fixing warped floorboards and reversing the damage is relatively easy. This article comprehensively covers how to fix warped wood floor.

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What causes wood floors to warp?

Warping describes the distortion of the shape of your wood planks. This plank disfigurement can manifest in several forms, such as curling at the edges (cupping), bulging in the middle (crowning), and gaps between the boards.

The most common cause of wood floor warping is water/moisture damage. An unidentified leak below the floor, water left standing for too long, and flooding underneath the house are all scenarios that can cause enough of a moisture imbalance leading to warping of your floor.

Temperature changes can also cause wood floors to warp. People living in areas with extreme temperatures may notice their wood floors start to warp in the summer due to the seasonal transition.

How to fix warped wood floor

The method of fixing your warped wood floor will depend on several factors, such as the type of flooring boards, their history, and the extent of water damage the wood floors have undergone.

While refinishing is one way of fixing warped wood floors, it may not be effective in all cases. The wood composition is one major factor determining whether you can refinish the floor. If you use engineered wood, the veneer will likely not survive the aggressive sanding needed to restore and straighten them. Similarly, in wood floors that had been sanded previously, sanding them may wear them down enough that they crack at the edges.

The size of the warp will also determine how you fix the damage. Small bumps in your wood planks usually characterize slight warps. Larger warps will take up more space along the plank, while giant warps are even more extensive and harder to treat. They are often caused by significant water damage and lack of proper care and maintenance.

Below is a comprehensive guide on how to fix warped wood floors.

  1. Fix the source of water/moisture

Repairing warped planks without addressing the source of the problem would be pretty pointless. Before undertaking any restorative options, you must find and stop the water source. This will prevent any further swelling and bubbles that may result in new damaged planks. Once the moisture levels are normal, you can start repairs on individual damaged planks.

Tip: If a bulged wood floor has not been exposed to moisture for long, you can reverse the damage. All you need to do is wipe off the excess water using a towel and a fan or dehumidifier to eliminate any excess moisture.

  1. Sanding

Sanding is most effective for small-scale warps from humidity and small liquid spills rather than leaks below the floor. Use a sanding block to sand down the bump until it levels out with the rest of the floor. You must realize that to smoot out a slight warp, rather aggressive sanding is required, and up to a quarter of the thickness of the wood may be lost. Therefore, sanding may not be the best choice in some circumstances.

  1. ‘Re-shape’ the wood

You can fix very small warps quite easily as long as the wood plank is still pliable. Moisten the areas slightly and then place a heavy object such as a cinderblock on top of the warped area. Leave the weight in place for a few days and then remove it to see if the warp is still present. If the warp is still there, treat the distortion like you would a large warp, as detailed below.

  1. Replace the affected planks

In cases where the first two methods are inapplicable or ineffective, replacing the warped wood planks and refinishing the entire floor to ensure uniformity is the best choice. Below is a detailed guide on replacing and refinishing warped wood floors.

Step 1: Remove the warped plank

Depending on the extent of the water damage, you may need to remove the whole plank or just a part of it. To partially remove the plank, set a circular saw to a depth of the board thickness and make a cut parallel to the damaged part. Pry out the strip that you have cut using a chisel or screwdriver while being careful to avoid interfering with nails holding the groove side in place.

Step 2: Replace the warped planks

First, you will need to acquire planks that are the same color and finish as the rest of the floor to ensure uniformity in the finished floor. Measure the size of the plank that you need. If replacing a full plank, push it into position and tongue it to fit the groove perfectly. Nail the plank edges until the nail is below the surface, and finish with good wood putty.

Step 3: Refinish the floor

Refinishing helps to ensure that the replaced plank is consistent in color and finish as the rest of the floor. Sand lightly using fine-grit sandpaper, then refinish it to match the other planks.


How to fix water-damaged swollen wood floor

Water damage can cause serious consequences, resulting in swelling of wood floors and buckling. While dealing with water-swollen wood floors is relatively simple, the repair process will likely take months.

Below is a comprehensive guide on how to fix water-damaged swollen wood floor

Step 1: Assess the wood floor swelling

Before taking any reparative action, you must first determine the extent of the damage. First, you must determine the water infiltration’s source and seal it off. After fixing the leak, then determine where the floor is buckling.

The floorboards are damaged if they look bowed, swollen, or if they have mold. Most swollen floorboards with minor damage can and will return to normal with some help. If the wood has split or come apart from the tongue and groove, you will need to remove and replace the floorboards.

Step 2: Gather the needed equipment and materials

If the damage is reversible, you must remove most of the water from the floorboards. The equipment and materials that you will need are:

  • A squeegee
  • A bucket and a stiff brush
  • Shop vacuum
  • An absorbent cloth
  • A pair of rubber gloves
  • A mild detergent and a compatible disinfectant

Step 3: Remove the surface water

Use the shop vacuum on wet mode to drain as much water as possible from the floor’s surface, and use the squeegee to gather the water as you vacuum it.

Step 4. Clean the floor

Use a mild detergent and compatible disinfectant to scrub the entire floor with the brush. However, do not pour more water onto the floor. Scrub until you remove all the mud, silt, and other materials that can promote mold growth.

Step 5: Treat any moldy areas

Use Trisodium phosphate (TSP) mixed with water to scrub areas affected with mold until all the discoloration and mold is gone. Rinse the boards with clean water, then wipe the surface with an absorbent cloth.

Step 6: Dry the floor

Increase the ventilation in the space by opening the doors and windows and running fans to help dry the floor. It would be best if you dried the floor slowly but steadily, as wood that dries too quickly can crack. Also, do not use heat to dry the floor as this can cause cupping and splitting.

Step 7: Sand

After the wood is dry, you may have some convex and concave floorboards. Use an orbital sander or sand aggressively with a sanding block to take down the small rises. However, if there is significant cupping, face-nail any aggressively curled floorboards back down.

Tip: Laminate flooring is highly susceptible to water damage. If you have water-damaged laminate flooring, we recommend replacing it.


How to fix cupping hardwood floors

Cupping, sometimes known as wash-boarding, is one of the milder forms of water damage. It happens when the edges of a plank along its entire length curl up and the middle sinks down. As with other forms of moisture-related damage, cupping is usually caused by a moisture balance. Cupping occurs when there is more moisture on the bottom of the wood pieces than on the top.

While cupped floors usually look unappealing, the damage is almost always reversible. You can fix cupping with the methods discussed below.

  • Allow the damage to reverse naturally.

For minor cupping, fixing the floorboards can be as simple as using a room to return the room to normal humidity levels. Since cupping is just the wood reacting to a moisture imbalance, the cupping can resolve itself if the wood’s moisture level returns to proper equilibrium.

  • Drying treatment

For more severe damage, you may need to invest in other solutions. You can use a professional drying treatment to return the floorboards to their normal shape. We do not recommend sanding cupped floors as this will cause more problems when the wood contracts again.

Tip: Drying the floor without addressing the real cause of the cupping is only a short-term solution. To truly fix the cupping, you must get to its actual source. Is the room too humid, or is the subfloor damp? Are there leaks? Dealing with the source of moisture will prevent cupping from reoccurring after you fix the problem.


What causes wood floors to buckle

Buckling is when the wood floor boards expand across their width, lift upward, and separate from the subfloor. It is one of the most extreme reactions to moisture damage on wood floors. Buckling may also manifest in several ways, such as a floor becoming uneven and the wood planks separating at the joints.

Apart from improper installation of the floorboards, several environmental factors also cause buckling. The leading causes of buckling are as discussed below.


In general, water and moisture are the most common reasons for buckling wood floors. Wood is a highly porous material. When wooden floorboards get wet, the wood fibers naturally swell to accommodate the increase in moisture. The wood moves upwards and buckles because of the expansion.

ii) Humidity

Humidity causes buckling in wood floors by the same action as water. Humidity is the amount f water vapor that is present in the air. Wooden floorboards will absorb moisture from the atmosphere and liquid water. In excessively humid environments, or rooms in the home, such as the bathroom, wooden floors will buckle. You can control the humidity in such rooms using fans and providing adequate ventilation. However, if the floors buckle or warp, you must replace them.

iii) Improper installation

Moisture barriers are critical during the installation of wooden floorboards. A moisture barrier is usually a thin sheet of polyethylene laid between the wood floor and the subfloor. Installation done without this will eventually lead to the floors buckling. Another critical part of the installation process is the expansion gap. A gap of ¼ to ½-inch needs to be left around the room’s perimeter to allow room for expansion and reduce the chances of buckling.

iv) Improper or no acclimation

Acclimation is allowing the wood to sit in the rooms where you will install it for a minimum of about two weeks. This allows them to adjust to the room’s average temperature and humidity levels. If the floorboards are installed without acclimation, they may contract or expand beyond the limits of the environment.

v) Temperature changes

Drastic temperature changes are also one of the causes of buckling in wood floors. Wood naturally expands with an increase in temperature and contracts with a decrease in temperature. The wood floor will likely buckle if these temperature changes happen too quickly between extreme ranges.


How to fix buckling wood floor

If you catch the buckling before the damage becomes too severe, you may get away without having to do extensive repairs. However, in cases where the damage is extreme, you will need to replace the buckled floorboards. Below are some of the ways you can fix buckling wood floors.

  1. Identify the source of moisture

Before you do anything else, you first need to address what is causing the moisture-related damage. Even if you had already installed the moisture barrier, it might be inadequate, especially in concrete subfloors. You will need to install a more efficient moisture barrier or use several different types together.

If the source of moisture is high humidity in the room, you can quickly fix this using a dehumidifier or by increasing the ventilation in the room. If you regularly wet, mop or steam clean your wood floors, this may be causing the buckling problem, and you will need to stop that. Leaks in the subfloor commonly cause extreme buckling damage. If this is the case, you will need to find the source of the leak and plug it.

  1. Minor edge curling

Once you have identified the source of the moisture, you can then proceed to repair and replace it as needed. If the buckling is minor, such as from high humidity or poor cleaning practices, the boards can return to normal when things dry out. Dry the boards on every level; dry the planks with a cloth, and the air with a dehumidifier. You can then place heavy weights on the buckled spot to accelerate the process.

  1. Partial replacement

If only a few floorboards have been damaged, and the subfloor is still dry, you can easily cut out the damaged boards and replace them with new boards without redoing the entire floor. Replacing some planks involve cutting the damaged boards using a circular saw, chipping them out, and tonguing in a new board. Also, remember to refinish the replaced boards to match the rest of the boards.

  1. Complete replacement

If the number of boards that are damaged is more than is practical for a partial replacement, the only way forward is to remove and replace the floor altogether. Even if most floorboards are in good shape, you must correct moisture problems in the subfloor.

  1. Prevention

Prevention is always better than cure. Knowing how to prevent your wood floors from buckling will save you so much money, effort, time, and frustration that fixing buckled floors bring. Below are some quick and easy tips on how to prevent your wood floors from buckling in the first place.

  • Check the moisture conditions of the subfloors.

Before you install any wood flooring, you must determine the moisture conditions of the subfloors and that of the wood flooring. It is critical to quality control. To do this, you will need a moisture meter. If you are concerned about damaging the floors, you can opt for a pinless moisture meter.

Test for moisture in several areas in the room, the plumbing and exterior walls, and average the results. A general rule is that a dry subfloor whose moisture content is less than or equal to 12% is ready to be worked on. Do not install the wood flooring if your moisture content readings are high. Ensure that you first determine the source of the moisture and deal with all moisture-related problems.

  • Cover the subfloor with a moisture barrier

Moisture barriers protect your wood floors from water wicking up from below, which could cause buckling and other moisture-related problems. It can be as simple as a roll of plastic sheeting, or you can use liquid solutions that are applied with a roller or a brush.

Moisture barriers are so crucial to floor protection that manufacturers of engineered floors, laminate floors, and solid hardwood floors require them as part of the warranty. Since concrete acts as a sponge and wicks water up from the ground and through the surface, a moisture barrier will direct the water towards the floor’s sides and vent it up through the walls.

  • Use the recommended type and number of fasteners.

When installing the floorboards, ensure that you use the recommended type and number of fasteners. Improper fastening will allow the wood too much room to move, while over-fastening might crack the planks.

  • Acclimate the wood

As mentioned above, acclimation allows the wood to adjust to the moisture conditions of the room in which you will lay it. Before you install the flooring, ensure that it is within the moisture content range recommended by the manufacturer. If it isn’t, allow it to acclimate for the specified time until it is within the specifications.

The video below illustrates how to repair warped hardwood flooring

Frequently Asked Questions (FAQs)

  • Will cupped hardwood floors flatten out over time?

If the cupping is not severe, hardwood floors can flatten out to an acceptable level after it dries, with very little cupping. Since cupping is just the wood’s reaction to a moisture imbalance, the wood can return to normal once the moisture conditions are in equilibrium.

  • Can you reverse wood floor cupping?

If the damage is minor, you can use a professional drying treatment to return the wood planks to their standard shape. However, before any repair, check the flooring for any looseness, as the stress from cupping can loosen the fasteners.

If there is looseness, one solution is to face-nail the loosened floorboards before refinishing them, especially for older floors. You can also reinstall the dried flooring.

  • How do you straighten warped floorboards?

To properly straighten warped floorboards (Curled at the edges or bulged in the middle), you will need to sand aggressively. You can use a drum sander with 20 grit sandpaper and sand diagonally, then parallel to the grain to remove the scratches. You then rub with finer grit sandpaper to prepare the boards for finishing.

However, it is essential to note that if the floor is severely warped, you may need to remove up to a ¼ inch of the board’s thickness.

With severe cases of warped floorboards, the only option you have may be to completely replace the damaged floorboards and refinish the floor for uniformity. However, if the damage is moderate or minor, you can reverse warping and have your floors looking beautiful again in no time.

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