Is subfloor ruined if it gets wet?

Author: Prof. Dax Heaney  |  Last update: Friday, January 30, 2026

A wet subfloor doesn't always need to be replaced, but it must be thoroughly dried and assessed for damage. Use fans and dehumidifiers to dry it out. If the subfloor is swollen, warped, or has mold growth, replacement is necessary.

Does wet subfloor need to be replaced?

Whether a wet subfloor needs to be replaced depends on several factors: Extent of Damage: If the subfloor is only slightly damp, it might be possible to dry it out and treat any mold or mildew. However, if it is extensively water-damaged, warped, or rotting, replacement is likely necessary.

How do I know if my subfloor is ruined?

When Should You Replace Subfloors? There are many signs that your damaged subfloor should be replaced with a new subfloor. These include squeaks and other noises, cupping or warping, cracked or popped tiles, sagging or unevenness, the smell of mold or mildew, or bubbling tile.

How long does it take for water to damage a subfloor?

If a leak or flood sits on your floor for 24 hours or more and/or reaches the edges of your floor and seeps underneath your flooring, it likely will need to be dried out completely. Usually, this will mean removing the flooring on-top of your subfloor.

Can plywood subfloor get rained on?

However, as with all other wood products, plywood should be protected from moisture and especially water, as it will soak that water up. A small amount of rain will not ruin plywood. A few showers of rain or a storm on your plywood will be ok as long as it is for only an hour at the most.

Level an uneven floor THE RIGHT WAY

Will subfloor dry out?

Whether your subfloor will dry depends on the level of damage it has sustained to the damaged sections. The best way to ensure that the subfloor will dry out, however, is to mitigate the initial issue.

Does wet plywood need to be replaced?

If the plywood is dried out quickly and efficiently, it can remain unaffected and undamaged in the long term, maintaining its full strength and durability for safe and reliable use.

Does homeowners insurance cover subfloor water damage?

Homeowners insurance generally covers water damage that's sudden and accidental. For example, if a pipe bursts or a washing machine overflows and damages your floor, you may be covered. But if the water comes from flooding, standard homeowners insurance typically won't cover it.

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.

What to do if water gets under flooring?

If you have water under your floorboards, remove floor coverings and dispose of damaged paper products, dry the area, clean and disinfect the soaked floorboards, ventilate the room, and contact a professional like ServiceMaster of Lake Shore for complete restoration services.

How much does it cost to tear out and replace a 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.

What is the life expectancy of a subfloor?

How Long Does Subfloor Last? Subfloor typically lasts 30 years or more, but if it is consistently exposed to moisture you may need to replace it sooner.

How to fix moisture in subfloor?

The first way that you can fix a subfloor moisture problem is by removing the finished floor and exposing the subfloor. Make sure that an HVAC system is installed or use a dehumidifier, and then, let the subfloor dry until the moisture levels have gone down.

Will plywood mold if it gets wet?

Rain and Its Effects on Plywood

This not only compromises the structural integrity of the plywood but also can lead to its eventual deterioration. Furthermore, the presence of persistent moisture can create a conducive environment for the growth of mold and mildew.

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

Squishy or spongy flooring can sometimes be a sign of water damage, either to the boards themselves or the subfloor. This is often caused by using too much water on the laminate to clean it, such as using a sopping wet mop or steam mop, which damages the wooden core of the laminate boards.

How do I know if my subfloor is damaged?

Sagging or Uneven Floors: A Clear Indicator of Structural Issues. Another critical sign that your subfloor may need repair is if you notice sagging or uneven floors. These issues are often more apparent in certain areas of the home, such as near doorways, in the middle of rooms, or along walls.

How long does it take for mold to grow on subfloor?

Mold growths, or colonies, can start to grow on a damp surface within 24 to 48 hours. They reproduce by spores - tiny, lightweight “seeds”- that travel through the air. Molds digest organic material, eventually destroying the material they grow on, and then spread to destroy adjacent organic material.

Does homeowners insurance cover mold?

Homeowners insurance doesn't usually cover mold damage or removal unless it's the result of a covered peril. If the mold in your residence was caused by something sudden or accidental, such as a bursting pipe or some other covered incident on your policy, you may be protected.

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 would a water damage claim be denied?

Reasons for denial can range from the nature of the damage itself—such as gradual damage that occurred over time—to issues with how the claim was filed, including missed deadlines or insufficient documentation. Furthermore, unreported property modifications can also lead to complications during the claims process.

Will insurance pay to replace the entire floor?

If only part of a surface is damage, such as a floor or siding, your home insurance may replace the entire surface if a close enough match can't be found. Some states have matching laws that require the insurance company to pay for a match or replacement.

Is wet rot covered by insurance?

Although not as serious as dry rot, wet rot has the potential to cause serious structural damage to your home if left untreated. This can be a time consuming and expensive procedure depending on the damage caused. Most contents insurance policies will not cover you against outbreaks of wet rot and dry rot.

How much does it cost to replace a subfloor?

Taking all these factors into account, subfloor material costs can range from as low as $2.50 per square foot for plywood to as high as $10 per square foot for Amdry or Barricade. Common subfloor materials include plywood, oriented strand board (OSB), Amdry, DRIcore, Barricade, Warmboard, and concrete.

How do I know if I have water damage under my floor?

If sections of your floor feel bouncy or soft underfoot, it could indicate water damage beneath the surface. This is often caused by prolonged exposure to water that weakens the subfloor, which can lead to costly structural repairs if left untreated.

How long does it take to dry out a wet subfloor?

Once it's wet, OSB takes hours to days to dry out. Keep your drying setup going until the OSB looks and feels dry. Then, start testing it with your moisture meter. Stick the 2 probes into the OSB and wait for the reading, and repeat the test at least 2 times per 100 sq ft (9.3 m2) of wet subfloor.

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