how to tell if floorboards are rotten
Kristina Davis

Learning how to tell if floorboards are rotten or the subfloor is getting damaged can save you a lot of hassle. 

You should check the condition of your floorboards often because they contribute to the stability of your home’s structure.

There are several telltale signs of decaying floorboards that indicate it is time to get rid of the old ones and put in new ones.

  • But, is it always necessary to replace them?
  • Will learning how to fix rotten floorboards save you time and money?

Well, if you are not sure, it is best to rope in the services of a professional. But, it is okay to play Sherlock first and look for certain signs. And what are they?

Your floorboards are likely rotten if they squeak loudly, feel spongy, smell weird, or show any signs of possible water damage. 

How To Tell If Floorboards Are Rotten Or Not?

how to tell rotten floorboards

The subfloor in many homes is made of floorboards, which are later covered with tile, carpet, linoleum, hardwood, or laminate flooring. Once the floorboards get old, they start making weird noises. 

Many people think that a creaking sound usually indicates a rotten subfloor, but the truth is that several factors contribute to the sound that older floors make. 

But, it is likely due to rot if accompanied by bumps in the floor caused by loose fasteners in the subfloor.

The urgency of the repair increases if the source of the lumps and creaks is rot.

The floor can be salvaged if you learn to recognize the signs of decay and act swiftly to stop it. 

Tip: Always talk to the installer and ensure that the planks they use are dry before installation to avoid dampness and water damage in the future. 

Is Creaking Always A Sign Of Rotten Floorboards?

Not really. 

Having clearly warped or fractured boards suggests something is not right with the subfloor. 

floorboard creaks

It is also a sign of rot if there are big spaces between the boards. The boards’ sponginess or softness underfoot is another red flag.

Damaged floorboards that have rotted away look quite old and used. In most cases, the wood is discolored and may have missing parts.

But if you do not notice these signs and still hear the creaking sound, it could be due to something other than the rot. 

Do Floorboards Creak When Not Rotten? 

Yes, it is possible.

Using too few fasteners, especially nails, can cause particleboard, plywood, and OSB subfloors to bubble up at the corners during installation.

The resulting bump is apparent even on a laminate floor, and may be felt on the carpet. And when you walk on it, it is quite likely to produce a creaking sound.

In the same way that particleboard can elevate due to insufficient fasteners or disintegrating subfloor, hardwood planks can do the same. 

Both of these flaws do not involve rotting in any way. 

Even if the moisture content is low, it can nevertheless cause the floorboards to swell and make noise while walking on them. 

how to identify rotten floorboards

How Do You Identify Rotten Floorboards?

So many things can go wrong during the installation process, which can cause all sorts of problems with the subfloor. 

But not all of them indicate rotten floorboards. Here are a few indicators suggesting your floorboards require your attention. 

Your Floorboards Make A Squeaking Noise 

As mentioned already, a squeaking sound is produced when the nails holding the subfloor to the joists are loosened.

The horrible, familiar sound of squeaky floorboards is caused by nails working their way in and out of the hardwood joists under pressure.

It could definitely be a lot less serious than rotting, but a room-wide squeaking sound may indicate that the material has become warped due to rotting. 

Tip: Invest in a high quality humidifier to keep indoor humidity levels in check and prolong the life of your wooden flooring. 

You Notice Moisture

notice moisture

The presence of dampness is the best indicator that a creaky and bumpy floor is deteriorating. 

If the flooring is made of hardwood, for example, signs of moisture may not be visible on the surface but can be seen through the boards. 

Also, if the floor is carpeted, you might pick up a musty odor. 

Similarly, lumpy areas are a sure sign of dampness, which could have been created by the subfloor expanding or the wood springing loose from its fasteners. 

You Notice Sponginess And Sagging

If you notice lumps alone, it could be the result of loose fasteners.

But, it is a different story if you also notice creaking with sponginess and sagging, which often indicates water damage.

There may be visible sagging, or you may need to step on the area to feel it. 

floor sagging

Subfloors that have been rotting for some time become spongy, and this lack of stability is immediately felt while walking on such a spot. 


You may notice sagging close to a lump in the floor if it is due to water damage because the rot can warp the subfloor. 

You Notice A Weird Smell

Finding the source of the mold or mildew odor is a challenge, but it is a sure symptom of water damage. 

Having a musty odor coming from your wood floor is a telltale sign of water damage to your subfloor. 

And when the water damage is severe, you just cannot save your subfloor from rotting. 

Your Notice Your Toilet Rocking

rocking in toilet

What is the connection between the rotting subfloor and your toilet? 

The rotting flooring no longer provides a solid base for the screws holding the toilet in place, so the fixture begins to shift. 

A dripping toilet or other source of persistent dampness is usually to blame.

There will be a steady deterioration till it is corrected, so you have to make a move soon.

Tip: Do not decide to replace too quickly because minor damage can usually be repaired by sanding the affected area and applying a new coat of stain or paint. 

You Find Hardwood Floor Cupping

A cupping hardwood floor sometimes indicates a high humidity level in your home, but in other instances, it may indicate water distorting the materials below it.

While it can be frustrating to deal with the issue, it is possible to have it repaired by experienced hardwood drying services.

And of course, eliminating the moisture source is vital too. 

You Have Leaks In The Ceiling

pipe leaks

The subfloor is not responsible for a leaking ceiling. Nonetheless, this could mean that your house has a hidden leak.

Any leaks in the ceiling could signify that the water damage is so severe that plywood around your house is soaked in it. 

If the subfloor has been damaged, it may be necessary to hire a flooring professional in addition to the plumber. 

Does The Wet Subfloor Need To Be Replaced Or Not?

It depends on many factors, but in most cases, you will definitely have to identify the root cause and correct it first. 

So many things can trigger the rotting of floorboards, which is why it is often necessary to connect with a professional to identify the root cause. 

Nevertheless, it could happen due to the following reasons and you have to fix them in order to prevent further damage. 

It Could be Due to Leaking Pipes

leaks in ceiling

Pipes that are leaking in damp areas such as basements, attics, and crawlspaces can always result in serious issues, often resulting in rotten floorboards.

Dry rot can easily germinate in these spots. 

It Could be Due to Excessive Humidity

Dry rot can spread in a structure due to a number of environmental factors, including condensation, penetrating wet, humidity, and rising dampness.

You have to fix these issues to stop any damage to the floorboards. 

Is It Necessary to Replace Wet Subfloor?

Replacement of subflooring due to damage is unnecessary in most situations.

Subfloor replacement is not always necessary if water damage is swiftly remedied.

In some cases, you may be able to save all or a significant section of your subfloors by employing remediation procedures such as quick structural drying.

replace wet subfloor

However, if floods or prolonged exposure to moisture causes substantial damage, it may be necessary to remove damaged areas to prevent mold and preserve structural integrity.

Subflooring replacement may sometimes be necessary because of things like fire damage or pest infestation.

And, of course, you have to replace subfloors if they have been damaged multiple times or where repairs were put off for an extended period of time.

Tip: Do not ignore any irregularities you notice through your linoleum floor because they can spread so quickly, leaving you no room for repair. 


Learning how to tell if floorboards are rotten can save you from spending thousands of dollars on repair work. 

Sometimes, the signs of water damage are obvious, but in other instances, they do not show up until it is too late to correct the issue.

So, be vigilant, and if you suspect water damage, do not waste time hiring a professional for a detailed inspection.