Water Damaged Subfloors: How to dry your floors and prevent mold growth

by | Jun 8, 2022 | Water Damage

If you have water-damaged subfloors in your home, you may be wondering what to do now that the floors are wet.

A subfloor that’s been soaked in water can become warped, sag or rot over time if not properly dried out and repaired.

The longer you wait, the more costly the repairs will be.

A subfloor is the base for any flooring material. It’s made up of wood or concrete that rests directly under the surface of the flooring material and above your foundation, crawl space, or basement.

They’re important because they support all other flooring above them and they also help regulate moisture and temperature in your home.

The most important thing to note is that if they get water damaged, you will need to dry out the flooring quickly because if left untreated, it can cause mold growth and structural problems.

More often than not, your homeowner’s insurance will pay for the cost of having a professional contractor handle the dry out and repairs of your floors.

In this article, I will explain the difference in subflooring and also show you how to dry them out yourself if you do not want to deal with or cannot use your homeowner’s insurance policy or pay cash to hire a professional.

Wood vs. Concrete

Wood is more easily damaged than concrete subfloors.

Wood subfloors are much more susceptible to damage or being ruined from flooding than concrete. The reason is wood will soak up some or a lot of the water and concrete is much more waterproof and its structural integrity will most likely not be weakened by a leak.

Also, even after several days of being soaked, the concrete will not buckle and crack. However, they can develop mold if they are not dried out quickly and properly.

Wood floors have a much greater tendency to get water damaged by being warped, buckled and/or mold growth. This is why you need to take action ASAP to prevent them from being ruined and avoid costly repairs.

Many wood floors today are usually made of OSB (oriented strand board) with an insulation layer placed between them and they usually are more difficult and can grow mold easier than regular plywood or concrete.

But the OSB won’t be completely destroyed by water. It will swell and shrink as it absorbs and releases water, so you should dry it out as fast as possible.

Mold Growth

Water damage to subfloors is also one of the most common reasons for mold to grow in a home or business.

When water floods a space, it creates an ideal environment for fungus to take root and spread. Even if you’re able to dry out your home or business quickly, there will likely be some residual damage from mold and mildew growth if it is not done properly.

If you’ve experienced flooding, you need to know how to safely clean it up to prevent mold growth and further damage to your home’s structure, or call a professional to handle it for you.

Here are 7 steps to dry your water-damaged subfloors:

1. Stop the source of the leak

The first step in dealing with water damage is to stop the source of the problem.

If you have a leaky faucet or toilet, fix it immediately. Make sure that all plumbing connections are secure and properly sealed. Check all drains and pipes for leaks as well.

In most cases, turning off the main water supply to your home or business and calling a plumber to repair the leak is the best course of action.

Turn off the power and remove any electrical cords from the area so that they don’t get wet again.

2. Inspect the damaged area

To determine how far water has spread, you need to get a good visual of the area and use your eyes and hands to touch the carpet to see it is wet.

It is best to use a moisture meter to measure how much moisture is present in the subflooring material.

This will help you determine if there are any hidden problems with your subfloors that need further inspection.

3. Remove soaked and wet items

Remove any wet items such as clothes, furniture etc.

Also remove any wet carpeting, padding and tack strip if necessary.

4. Remove standing water

If there is standing water in the room, use a wet-dry vacuum to suck up as much water as possible. You’ll also need to remove any remaining standing water — which could contain mold, bacteria or harmful chemicals.

If you do not have one, use towels to soak up as much of it as possible before continuing with repairs.

5.  Clean with antimicrobial solution

As soon as you clean up the water, you should spray the area with a good antimicrobial solution to kill any mold spores, bacteria or other microorganisms that may be present. This will help prevent mold growth as well.

6. Dry out the area quickly

Once that’s done, you need to dry out the area so that it doesn’t continue to get wet.

Dry out your home by using fans and dehumidifiers to take moisture out of the air and dry out wet materials like wood floors, carpeting and drywall.

Wood floors and concrete floors can take several days (3-7) to properly dry before you want to make repairs.

7. Inspect floor

Inspect the subfloor for signs of rot or other structural damage that has been caused by excessive moisture.

If there are cracks in the floor joists or walls, then you will need to have them repaired before installing new hardwood floors.

Check for sagging floors. Sagging can occur as a result of water damage, and that means repairs to the subfloor and/or floor joists will most likely need to be repaired or replaced.

You may be looking at joist replacements, which are boards that run horizontally below the subflooring. They’re critical to the structural integrity of your home.

Average Cost for Repairs

The average cost of repairing a small area of flooring is approximately $500 to $1,200 depending on the area of the U.S. you live.

If significant repairs need to be made, such as replacing all the subfloors and joist repairs, this can cost as much as $6,000 to $12,000 for a small room.


If you’re concerned about taking care of water-damaged subflooring by yourself and would like to hire a professional, please contact me 24/7 at 760-818-6830.

My team can take care of the damage and repairs all across San Diego and Orange counties. I also offer professional consultations for $100 per hour.


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