What Cause Cupped Wood Floors: How to fix and prevent

Any type of flooring is subject to vulnerability, and cupped wood floors are no exception. In general, cupped wood floors are a condition where the wood floors react to excess moisture levels.

It doesn’t take rainfalls from broken attics to experience cupping on a wooden floor surface. Stains that sit for too long and several other activities that leave the flooring surface wet can cause cupping problems on the wooden floor’s surface.

Floating wood floors with more than one layer of natural wood can bend and warp. In technical terms, this deformation, called “bowling,” is almost always caused by the same things.

More specifically, here are things that cause wooden floors to get cupped:

What are things that cause cupped wood floors?

Moisture is the enemy of all wood floors, whether they are glued down or float on top. This is more about the moisture under the floor than the moisture on top! Wet subfloors cause about 85% of the damage to wood floors.

There are many different kinds and sources of water. So, it’s not always easy to figure out what’s happening.

Residual moisture

Residual moisture is a problem when the subfloor is touched up with screed about 15 days after putting down the new wood floor.

With screed, the subfloor is made level so that the wood floor can be laid in the best way.

But with screed, you have to think about how long it will take to dry, depending on ventilation, how warm the room is, etc.

Moisture left behind can only show up after some time has passed.

However, you can avoid this issue by checking the floor with a moisture meter before laying it.

Professionals always have this tool with them; before they lay the floor, they have to check the subfloor. The subfloor must have less than 3% of water in it.

If moisture is still in the subfloor, it will get through the wood floor to the outside. Your new floor will get damaged and warp a little or a lot.

Moisture in the subfloor

Subsurface moisture, like residual moisture, doesn’t only affect buildings that are brand new. On a new traditional substrate, like a cement screed, give it at least 1 mm daily to dry.

So, if you have a substrate that is 10 cm thick, you have to wait at least 100 days unless you speed up the drying process. But you still need to check with a moisture meter before laying.

If you don’t, there is a good chance that your floating wood floor will get wet and change shape.

A vapor barrier is always used when putting down a wood floor. But this doesn’t stop enough water from getting in. Before putting down the wood floor, the subfloor must be sealed to keep out moisture.

Water damage

The moisture comes from above and hits your floating wood floor floor! When there is water damage, the water usually sits on the floor for a while, so the floor gets wet.

The floor doesn’t buckle immediately; it only does so when the water dries up.

So, to figure out how bad the damage is, you need to wait until the wood floor t is completely dry.

These can be easily replaced if the warping only affects a few planks.

Dry and humid air

Air that is too dry or too wet can also cause your wood floor t to warp.

Although a floating wood floor is more stable than a glued wood floor, it can warp if humidity levels are too high or too low.

Once you know what’s wrong, it’s usually enough to change the humidity in the room for the wood floor to return to its original shape. But this solution will only work if your parquet hasn’t warped too much.

For putting down a parquet floor, the humidity should be between 45 and 65%.

Missing expansion joints

The floating wood floor can’t stretch enough, which is the second reason why it’s warped. The wood floor must not touch a single element. It must have enough room to grow on its own. For this, you must know how far away the wall is. These so-called expansion joints have to be at least 8 mm wide.

There must be expansion joints everywhere: around the door frames, on every wall, around the heating pipes, where one-floor covering meets another, etc. Just about everywhere, there’s something in the way.

Putting in a floor without expansion joints is a big mistake. In this case, the wood floor is pushed up against the obstacle.

Just one point is enough to make the whole floor warp. When this happens, your wood floor turns into a trampoline.

Here are other reasons why cupped wood floors can happen:

  • Failure to adjust the hardwoods’ climate conditions to the environments according to the manufacturers’ standards.
  • Immediately install the hardwood floors before acclimating them.
  • Not immediately dry the floors after mopping them.
  • Too many spilled forms of liquid substances, including but not limited to water, milk, juice, syrup, and the like, that we don’t clean up immediately. As a result, these liquid substances sit too long and change the surface’s patterns.
  • The water is leaking out from the room’s air conditioner.
  • The broken attic remains unfixed and causes rainwater to fall into the room (Note: This can happen with the leaking water from the air conditioner).

How can we fix cupped wood floors?

The good news for cupping problems on a wood floor is that we can fix them as long as we have the necessary things and follow the step-by-step instructions.

The most important step is locating and eliminating the problem’s root. If this aspect is overlooked, it is almost probable that deformations in the wood floor will occur again and again.

First thing first, here are things we need to fix our cupped wood floors:

  • A dehumidifier
  • A damp cloth or a paper towel soaked in water to dampen the dry side of the wood
  • Some extra boards of hardwood (in cases of wood replacements)
  • Other safety work items, including goggles, flashlights, and safety gloves

Then, follow these instructions to fix the cups in the wood floors:

  1. Examine, set, and adjust every button on the dehumidifier levels to correct the moisture balance. Repeat the step until we get the desired balance.
  2. Use a damp cloth or a paper towel with enough water according to the hardwood boards’ thickness to wipe the dry side of the wood. Repeat until you’ve got the entire dry side wet.
  3. Isolate the damp wooden board on a face-down position on an outdoor flat countertop.
  4. Let the wooden board sit for 24 hours. Or, repeat Steps 2 and 3 consecutively until the wooden board dries.
  5. Repeat Step 1 to adjust the wooden board’s temperature to the environment.

If your wood floor has too much cupping, the planks will bend so much that they will break. In this case, the wood floor has to be replaced all the way through.

What can we do to prevent our wooden floor surfaces from cupping?

Now that we know the reasons behind cupped wood floors, here are the preventive things we can do to ensure the same mistakes don’t happen at all times:

  • Pay attention to the wood’s characteristics that you’re about to install. It will be nicer if you purchase acclimated wooden floors. If not, allow some “cool down” times for the wooden boards before installing them.
  • Place an air conditioner, a dehumidifier, or a medium-to-large fan in the room. These two must work together to regulate the room’s and the wood’s temperature.
  • Don’t procrastinate in cleaning up. Cleaning up the floor shouldn’t stay as the only daily chore. Instead, clean up as soon as you notice stains on the floors.
  • If you plan to install wooden floors in kitchens, dining rooms, or bathrooms, turn on the vents after cooking or showering for a while.
  • Be careful in sanding the floors to prevent cupping and crowning.
  • Don’t hesitate to ask professionals for help and sales teams for more information about the wooden product you purchase.

What are the rules for sanding wooden floors that are already cupped?

Sanding cupped wooden floors requires us to be extra careful. The positive side we can get from doing such a thing is that we can flatten the cupped wooden floors’ surfaces. At the same time, sanding the wooden floors flat when they have been cupped can pose another problem: a crowning wood floor.

A crowning wood floor can look worse than cupped wooden floor surfaces because their convexness is deeper than the previously cupped surfaces. Crowning typically forms when the sanded floors have dried and we’ve finished sanding cupped floors. Additionally, crowing problems frequently happen if we don’t dry the wooden floors’ surfaces.

We can only sand-cupped the floors when the cupping problems are so severe that we can no longer fix them. Winter seasons are ideal for sanding our already-cupped floors due to the lower and more balanced temperature and humidity levels than in summer.

When we sand our cupped wood floors, the ideal limits for the sandpaper grits’ amounts would be around 36-80. We should only apply the maximum grit amount, 80, after vacuuming the entire flooring surfaces at least two times. For your information, you can get sandpaper grits in such amounts in most supermarkets and nearby stores.

Light sanding

A light sanding might be enough if the floor is slightly out of shape. But remember that you’ll need to treat the wood floor afterward. This can be very hard to do if the wood floor is stained.

Heavy sanding

If the wood floor is warped, sometimes the only way to fix it is to sand it very hard.

If your wood floor has a slope, it will be lost if you sand it too much. Doing this will take away about 1 to 2 mm of wood, the depth of a slope.

Once the warping is gone, you can protect the wood floor by re-oiling or varnishing it. You can now also change the color of your floor if you want to.

How to dry out cupped hardwood floors

After we have eliminated the excess water that threatens to produce short-term difficulties in our wooden floor, we must focus on ensuring that no moisture is left under the slats that could damage our floor. You can accomplish this by following these two suggestions:

Ventilate the room

When this flooring gets wet, it’s crucial to promptly wipe it up and air the space by opening windows and doors. This will allow the floor to dry naturally and prevent moisture from seeping into the house.

Use a heat source 

Suppose we have been unable to dry the water promptly, which has permeated between the joints.

In that case, the best choice is to apply hot air to the region, which we may do with a hair dryer, concentrating on the joints between the slats or the glued sections to doors or walls that may have been impacted.

Although the temperature of your dryer should not be hazardous to the wood, take care not to harm or burn it.

How long for cupped floors to dry

Don’t pay quickly to fix problems with cupping and camping in new flooring. Sometimes things will work out in the end.

If I sand a floor that would have stabilized and flattened on its own, you will have a new problem when the floor does stabilize. Let the wood dry out.

When the moisture level returns to normal, the flooring should return to its former size and shape as long as the wood has not been irreversibly distorted or damaged.

This could take a few weeks, months, or even the whole heating season. Sanding shouldn’t happen until all the moisture levels are back to normal.

As a general rule, if the top and bottom of the flooring have different amounts of moisture by 2% or more, it is probably not done drying.

Dehumidifier for wood floors

A dehumidifier can help eliminate some moisture when there is much water on hardwood floors. This is especially true for places that aren’t sealed.

You can use a personal dehumidifier, but if there is much flooding, you will need to rent a commercial dehumidifier.

Keep all nearby windows and doors closed when using the dehumidifier.

Desiccants for wood floors

Desiccants are materials that soak up water and can be used to dry out damp places. Dry out desiccants by putting them in cabinets or other areas where air doesn’t move.

Different desiccants include kitty litter made of clay and calcium chloride granules. You can buy them at any hardware store or drug store.

Fixing Cupped laminate floor

When enough water gets on the floor, it can damage many kinds of flooring, not just laminate. When water falls on solid wood floors, they will warp and swell. Since the wood fibers in natural wood run in one direction, the direction where the wood is weakest is on the side.

When wood bends in this way, it is said to be a “crown” or “cup.” Waterproof floors, like vinyl, can be damaged if water gets under the floor and starts to break down the paper backing.

Real wood may be used again instead of laminate, which cannot be. Sanding can flatten even cupped or crown-shaped wood.

You can’t sand laminate floors. Does that mean there’s no way to fix it?

Broken boards can’t be fixed, but they can be replaced one at a time. Most installations use boards that have been laminated.

Since each package has a set number of boards, some will always be left over.

Although laminate flooring may resemble solid or engineered hardwood, it is not the same material.

It is usually necessary to replace laminate flooring harmed by water.