How to tell if a subfloor is rotten?

Author: Lelia Brekke  |  Last update: Saturday, February 22, 2025

Signs Your Subfloor Needs to Be Replaced
  1. There's a Musty Smell. ...
  2. Your Floors Squeak. ...
  3. The Floors Are Uneven. ...
  4. You Can Feel the Floors Move Beneath Your Feet. ...
  5. Your Tile Floor Has Broken Tiles. ...
  6. Your Linoleum Appears to Be Bubbling. ...
  7. Your Wood Floor Is Cupping. ...
  8. The Toilet Is Loose.

How to know if a subfloor is bad?

Top 3 Indicators of Damaged Subflooring in Your Home
  1. Noticeable Squeaking and Creaking Sounds. One of the most common indicators of bad subflooring is an increase in noise. ...
  2. Uneven or Bouncy Floors. ...
  3. Visible Water Damage or Mold.

How many years does a subfloor last?

There are many factors that can affect its longevity, such as the material, the amount of moisture it's exposed to, etc. However, most subfloors can last as long as the home itself. That said, you may have to replace your subflooring after 20 to 30 years if it has absorbed too much water too often.

Is my subfloor rotting?

It's difficult to assess if the sub-floor is rotting until carpets or tile are pulled back and an inspection is conducted. However, if the sub-floor feels spongy and sags when walking across the floor, this is a sign of a rotted sub-floor.

Why does my floor feel spongy when I walk on it?

The hollow/spongy patches aren't caused by sagging. The floor is trying to expand, but is being pinched at the edges because there's not an adequate expansion gap where the floor meets the walls, so it buckles upwards.

Unbelievable Secret to Fixing a Damaged Subfloor in Minutes!

Why does my subfloor feel soft?

Water damage to your subfloor can cause soft spots over time. Repairing the damage quickly can help your home avoid soft spots and problems with sunken areas in the subfloor. Get help from the professionals at BAY Crawl Space. Watch for the signs of water damage so you can get your house help from a pro.

What does rotting subfloor smell like?

Wet rot is more likely to smell than dry rot. It has a damp, musty smell that has been described as smelling earthy and like rotting soil.

Does insurance cover rotted subfloor?

Generally, no. Insurance would cover a sudden loss event. A slow leak causing rot over an extended period of time is not a sudden loss event.

What does termite damage to subfloor look like?

Signs of termite damage

If termites start to snack on your home's joists or subfloor, you might notice sagging floors — or hear them creak more than usual as you walk on them. Similarly, termites eating away at wall studs and ceiling beams could cause the ceilings and walls to buckle.

Who to hire to replace a subfloor?

Given the complexity of subfloor repairs, you should really stick with a carpenter for this project. But if you want to install a new subfloor or underlayment over sound floor joists, hire a local flooring contractor for this step.

How to tell if a subfloor has mold?

Subfloor mold often shows up as dark spots or patches under your floors. You might find it under carpets, vinyl, or laminate. The mold can look like black, green, or white marks on plywood or OSB, which are common in homes since the 1950s. A musty smell is a sign of subfloor mold.

Can you replace rotted subfloor from underneath?

While it may seem tempting to replace the subfloor from underneath if your home has access from the basement to this area, it should always be replaced from the top.

How do I know if my floor is rotting?

Detecting Rotten Floorboards:

Here are some signs that indicate potential rot: Soft or Spongy Spots: Walk across your floor and take note of any areas that feel soft or spongy underfoot. These spots are likely caused by water infiltration and may indicate rot.

What does water damaged subfloor look like?

The most obvious is a spongy feel or “give” to the affected area. Other signs of water damage include warping in the floorboards of your hardwood floors, loose sections in your tile floor, bubbling or peeling in linoleum, lifting in your laminate flooring, or a musty smell that could indicate mold growth.

How do you test moisture in a subfloor?

You can check this quickly using a pinless moisture meter. The subfloor materials should be within 2%–4% moisture content of the floor. If they aren't, allow them to acclimate until they're within that range.

How much does it cost to replace rotten subfloor?

For an average-sized room of 300 square feet, expect to spend about $900 to $3,000 on the cost to replace subfloors, or $3 to $10 per square foot. Most homeowners spend about an average of $1,560.

Does subfloor rot spread?

Once dry rot occurs, it can quickly spread to nearby wooden structures, causing further damage and increasing your repair costs within a surprisingly short period.

Will homeowners insurance replace flooring?

Does homeowners insurance cover carpet and floor damage? Home and condo insurance typically covers floors and carpet if the damage was caused by a covered peril.

How to tell if a subfloor needs replacing?

If your floors begin to feel spongy, springy or bouncy, or if you notice the floorboards around you shifting when you walk on them, it could mean that it's time to replace your subfloor.

Can you stop wood rot once it starts?

Can wet wood rot be repaired or treated? Wet rot is often less damaging than dry rot. Typically, when you eliminate the source of moisture, the rot stops spreading. Once the moisture is eliminated, applying a fungicide like borax will help ward off fute wet or dry rot.

How do I keep my subfloor from rotting?

How to protect your crawl space from wood rot
  1. Use a commercial subfloor sealing product like LumberKote to make exposed wood water resistant.
  2. Keep your rain gutters and downspouts in good repair.
  3. Inspect your crawl space at least once a year for signs of excess moisture.

Does wet subfloor need to be replaced?

In most cases, damaged subflooring doesn't need to be replaced. However, in the event of extensive water damage from flooding or extended periods of exposure to moisture, damaged sections may need to be removed to avoid mold and ensure structural integrity.

Why do my floors feel bouncy when I walk?

Causes of Bouncy Floors in Your Home

Over Spanned Joists: Joists supporting floors above crawl spaces may be spaced too far apart or be too long, causing excess flexing. Inadequate Support: Insufficient support structures like poorly installed or shifted posts and beams can lead to bouncy floors.

What should my subfloor look like?

The subfloor is typically made of plywood or OSB, ranging from 19/32 inches to 1-1/8 inches thick. Subfloor plywood or OSB sheets typically have tongue-and-groove edges to reduce floor sagging and bounce. If the bottom-most floor is a concrete slab, its definition as a subfloor becomes more fluid.

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