Hardwood Floor Buckling from Water Damage -Causes & Repair

Wondering what are the First Signs & How to Tell if Your Hardwood Floors have Started to Buckle after water damage?

Do your hardwood floors feel uneven, look rippled and wavy?

It may be that your flooring has started to buckle from water damage.

In this article, you will learn not only the common causes of Buckled Hardwood Floors but also what can be done about them and how to repair them.

The Common Signs of Buckling Hardwood Floors


Buckling is where the wood has absorbed moisture on one side more than the other.

This is often a result of flood damage, especially long term moisture absorption.

The number and position of the floor fixings will affect how the floor appears.

On a glued floor, the entire surface may rise as the top or bottom layers expand, with grooved floorboards, it may just be bowing on the linear axis of the board.


Hardwood cupping is where the edges of a board become higher than the centre.

This is usually because of the bottom surface expanding due to moisture intake.

It can also be caused by a saturated board being dried from the top surface only, causing this side to contract.

This force pulls in from the top face and curls the board upwards.


Crowning is the opposite of cupping, where the top surface of the board is saturated, causing expansion.

This then causes the top face to curve downward.

Common Causes of Buckled Hardwood Floors

Buckled flooring can be extremely difficult to remedy, but it is important first to source the cause of the problem.

If the root cause is not addressed any attempts to fix the issues will be pointless.

1. Flood damage

This is the most common cause of buckled flooring.

When water enters a property in-mass as in a flooding situation it can be extremely tricky to remove it.

Even once most of the water is drained or pumped away, porous substances like wood and furnishings will retain water.

Many hardwood floors are fitted with an underlay underneath to level the floor.

Depending on the type of underlay used it can be very porous and absorb water well.

It is therefore often necessary to lift hardwood flooring and replace the underlay.

This is expensive and timely, though and many people will opt for air-drying the floor.

This can sometimes work, but often will result in the top layer of wood drying, and the underside remaining wet.

This is the ideal circumstance for Buckling to occur.

2. No Moisture barrier

When fitting hardwood flooring it is important to keep away water of all sorts.

This includes residual water from the air and ground.

In houses with beam flooring especially, moisture from the atmosphere in humid climates causes wood to expand.

If your home also has air conditioning, the flooring is now acting as a barrier between moist air, and dryer cool air.

The proper method when this situation occurs is to use a moisture membrane under the floor.

This ensures the moisture cannot rise into the wood flooring, and cause the bottom side to expand.

Even rips or tears in this barrier may cause this, so if your hardwood flooring is suffering from buckling, it is advisable to check your moisture retarding layer.

3. Incorrect Fasteners

All wooden objects will contract and expand with heat and moisture.

It is one of the main issues and complexity to woodworking in general

If the boards are fastened to the sub-floor insufficiently, the expansion will cause gaps once the wood has dried out completely.

Conversely, if the floor boards are fixed down too tightly, the wood will still try to expand and may be at risk of cracking and buckling/cupping.

It is best to adhere to the manufacturers guidance on when and where to fit fasteners into wood flooring, paying special attention to your climate and environmental factors.

4. Incorrect Fitting

A moisture meter is a good investment to make when attempting to fit hardwood floors.

It can tell you what the current moisture content is of the subfloor, and the wood you are fitting.

The manufacturer of the flooring will give advice as to the compatibility of subfloor and wood moisture levels.

If the wooden flooring is fitted to an excessively damp subfloor, the underside of the floor boards are always going to absorb this moisture, resulting in a warped and buckled surface.

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Can Buckled Hardwood Floors Due to Water Damage be Repaired?

With minor buckling there is the possibility of sanding and refinishing, this is removing the uneven surface until flat, then re-applying a sealant such as varnish or epoxy.

Hardwood Floor Got Wet and Buckled – How Bad is it?

The level at which a hardwood floor will buckle will depend on various parameters including the ambient moisture level, ambient temperature, amount of water absorbed and time taken to dry the boards.

Inspect the boards for buckling and cupping, variations over ¼” across a single board will likely be too far gone to repair, and may need professional drying and planing to be fit for use.

If this is the case it is often easier to fit new boards.

If only a slight amount of buckling is noticed, it may be possible to sand back the boards, see the next segment for info.

How to Repair Water Damaged Buckled Hardwood Floors

It may be possible to remedy a warped and buckling floor yourself, the steps below lay out the process including any tools needed.

Tools You May Need:

  • Moisture tester
  • Pry bars
  • Screwdrivers
  • Spirit level or straight edge
  • Measuring Rule
  • Chopsaw
  • Hammers
  • Fixings eg. nails or screws

1. Fix the moisture problem

The first step to fixing a buckled or water damaged floor is to identify the cause of the leak.

This way any work you complete to remedy the problem will be worthwhile, and not ruined by a recurring problem.

Common sources are leaking taps or bathroom fittings, condensation build up from windows, and tears in moisture retarding membranes allowing humidity from the atmosphere.

2. Dry the area & Your Hardwood Floor

The room should be cleaned of furniture and other items, and allowed to dry.

It may be required to use a dehumidifier to aid this. These appliances remove moisture from the air, depositing it in a reservoir that needs emptying regularly.

The moisture-free air will encourage the floorboards to dry out actively into the room.

It is therefore essential that the room is kept well ventilated, if a dehumidifier is not used.

This process may take a few days up to a couple of weeks, depending on ambient temperatures and climate.

This process cannot be rushed, however, as wood will only lose moisture at a set rate per hour, and needs to be completely dry (or dry to the manufacturers standard) before continuing.

3. Assess the damage

The level of warping needs to be figured out in order for the correct course of action to be taken.

Minor buckling may only require sanding, whereas major damage will need to be replaced.

A moisture tester should also be used to ensure the floor is back to the ambient or consistent moisture level.

This is to make sure the problem is at its worst, and is not still ongoing.

4. Repairing Minor Damage

If the buckling is only small – less than ⅛” across a board, it should be possible to sand and recoat the surface:

You will need a high powered or industrial floor sander. It may be best to hire one of these as they can be costly.

  • Clear the room of all furniture
  • Tape off any areas of the house not included in the room to be sanded – the dust will travel and be difficult to clean
  • Sand using a course paper, 40-60 grit, across the whole area evenly, not focussing on one location excessively.
  • Take further measurements using your straight edge, to asses the improvement.
  • Once the cupping or buckling is returning to flat boards, increase the sandpaper grit level
  • Keep increasing the level until the boards are smooth, this will depend on your preferred finishing technique; a varnish may require a very smooth surface, whereas an epoxy less so – consult the manufacturers guide for prepping
  • Coat in preservative of choice

5. Repairing Major Damage

If the boards are cupped beyond ⅛” it may be easier to replace, it would be impossible to return this to be completely flat, and would take many many hours to achieve, even with industrial equipment.

  • Remove all furniture
  • Assess the damage – are all the boards buckled, or can a section be replaced? (when considering this, be wary that the entire floor may still need sanding and refinishing, as sunlight fades treated hardwood)
  • Remove floorboards as necessary, being careful not to damage the sub-floor
  • Assess the sub-floor, this may have been the cause of the problem, if it is damp it will need to be dried out sufficiently
  • Assess the moisture retardant membrane (if present) again, this will cause future issues if not working correctly.
  • Re-fit new floorboards. These should be fitted as per the manufacturers guidelines regarding moisture levels, subfloor protection etc, each product is slightly different.
  • Finish if required with oil, varnish or epoxy

Preventing Wood Flooring from Cupping & Buckling in Future

Once you have fixed your buckling hardwood floor issue, it would pay to take measures in ensuring it does not happen again.

As mentioned, subfloor moisture retardant layers are often required depending on the sub-floor used.

It is also generally beneficial to ensure all water fittings, appliances and connections are serviced and maintained regularly.

A leaking radiator or boiler could be undetectable immediately, but water can often run behind furniture and appliances, and build up in areas un-noticed.

When to call a professional

It can be a hard decision as a DIYer to call in the professionals, but in the case of hardwood flooring it is often best to at least consult before tackling yourself.

What seems simple at first could end up being a large problem, and crucially, if the underlying causes of the buckling are not addressed, the problem may return, resulting in a loss of time, effort and significant cost.


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