Water Damage Subfloor. Tips from professionals
When you find your floor flooded with water, a lot of things can go through your mind. You probably hope that the damage is not severe. The worst-case scenario is that the water has been standing in the room for a long time and has soaked into your subfloor. If you need to replace the subfloor, it can turn into a big job.
How Do You Fix Water-Damaged Subfloor:
- Step 1: Assess The Damage
- Step 2: Mark The Area
- Step 3: Cut Out The Damaged Areas
- Step 4: Add The New Flooring
- Step 5: Install Flooring
Not only do you have to worry about the actual subfloor, but you also need to remove your flooring and may have to worry about structural damage as well. If you find that your subfloor is damaged, I recommend following these steps to fix it.

In this blog post, I will explain the steps in more detail. And how you can know if a subfloor needs to be replaced and the best way to remove the moisture.
Contents
- 1 How Do You Fix Water-Damaged Subfloor?
- 2 How To Tell If The Subfloor Needs Replaced
- 2.1 ● Signs Subfloor Needs Replacing: Floor Looks Uneven
- 2.2 ● Signs Subfloor Needs Replacing: You Can Feel The Floors Moving
- 2.3 ● Signs Subfloor Needs Replacing: The Floorboards Squeak
- 2.4 ● Signs Subfloor Needs Replacing: Furniture Is Uneven
- 2.5 ● Signs Subfloor Needs Replacing: Cupping
- 2.6 ● Signs Subfloor Needs Replacing: Leaking Ceiling
- 2.7 ● Signs Subfloor Needs Replacing: Bad Odors
- 3 Will Wet Subfloor Dry Out?
- 4 How Do You Get Moisture Out Of A Subfloor?
How Do You Fix Water-Damaged Subfloor?
If you have had a flood or a pipe has burst in your home, there’s a good chance the subfloor may be damaged and need to be replaced. Follow these steps to help you replace it if your skills are up to it. If you are less experienced or do not have enough time, I recommend asking a professional for help. In some situations, the subfloor damage can be challenging to check and replace if needed.
● Step 1: Assess The Damage
It’s always a good idea to get a good look at things before you start any repairs. Be sure to pull up the flooring in your home so you can have a good look at the subfloor. Once you know how bad the damage is, you can come up with the best way to repair or replace it.
● Step 2: Mark The Area
Take some time to inspect the area and mark the parts that need to be replaced. You may not need to replace the entire floor, but you will need to work on the damaged sections. You should measure and mark with a piece of chalk or a marker.
● Step 3: Cut Out The Damaged Areas
Use a saw to cut out the damaged areas. Be sure to make your cuts clean so you can easily fit in the new subfloor. The more accurately you measure and the straighter you cut the damaged pieces, the easier adding the new subfloor and the better the finished result will look.
● Step 4: Add The New Flooring
Put your new flooring in the proper location. Be sure to secure it in place and pound flat any screws or nails that could be sticking up. The new subfloor should fit right in the space of the old portions that were removed.
● Step 5: Install Flooring
If you plan to install new flooring over the sunflower, you can do so. Be sure to clean up the area to ensure no dust or dirt could prevent the new flooring from adhering to the subfloor or cause lumps and bumps that might lead to more damage.
Do You Have To Replace Wet Subfloor?
The subfloor may not need to be replaced as long as you are able to remove the water quickly. It takes some time for the water to get under your surface flooring and damage it. By removing the water quickly, you won’t have to worry about it damaging the subfloor. Of course, it also depends on the type of subfloor. When it is, for example, made from concrete, you have less to worry about.
How To Tell If The Subfloor Needs Replaced
If you notice the water has been on your subfloor for a while, you may need to replace the subfloor. Before you start working on your floor, be sure to check for some of these issues that will tell you the repairs are necessary:
● Signs Subfloor Needs Replacing: Floor Looks Uneven
Check the floors to see if any parts look uneven. You may notice that some areas appear to be sunken in, or some parts are higher than others. It could mean the subfloor is damaged and will need to be replaced.
● Signs Subfloor Needs Replacing: You Can Feel The Floors Moving
If you step on the floors and feel them moving, it may mean you need to replace the subfloor. The subfloor can be soft in some places and may give out when any weight is put on it. It can take some time for the floors to become soft or loose enough to shift, but once it starts to happen, it can affect the entire floor.
● Signs Subfloor Needs Replacing: The Floorboards Squeak
There are many reasons your floors may squeak, but if you recently had a flood or a leak and there is a chance the water could have gotten into the subfloor, the squeak could be a sign that it’s time to replace it. The squeak will likely get worse as time goes on, and it could be really noisy in your home.
● Signs Subfloor Needs Replacing: Furniture Is Uneven
You likely have furniture in your room, and if you notice that it no longer sits right and seems to be tilting or uneven, it may mean the subfloor is weak. Furniture is heavy, and if the flooring is soft, the furniture may be sinking into it and even poking through it. Even if the leak or floor didn’t occur in the same room, it might have spread to that area and made that subfloor weak.
● Signs Subfloor Needs Replacing: Cupping
If you notice cupping on your floor, it could mean that there is still water in the subfloor or that the subfloor has become so weak it can no longer support the flooring in your home, and it is starting to buckle from the weight. In some cases, you can make repairs, but you may need to replace it if it is severe.
● Signs Subfloor Needs Replacing: Leaking Ceiling
If you are in a house that has more than one floor, and you notice the ceiling above you is leaking, it may mean that the flooring on that floor is damaged and needs to be replaced. A leak could cause this in a pipe or a flood in the bathroom. You may not even know there is damage to the floor until you see the water dripping from the ceiling. This might also mean that you need to replace your ceiling.
● Signs Subfloor Needs Replacing: Bad Odors
You won’t always see signs that your subfloor is damaged and needs to be replaced. Sometimes you will smell the signs first. If you walk into your room and notice there is a musty or moldy smell, it may mean that the water has made it down to your subfloor. Mold may be growing and causing the smell, or there may just be water inside the subfloor that you can smell when you walk into the room.
Will Wet Subfloor Dry Out?
Your subfloor will dry out in time, but the sooner you can dry it, the less likely there will be as much damage. The longer the water is left on the subfloor, the more likely the floor will swell and become damaged. Once the subfloor has absorbed enough water to swell, it may have to be repaired or even replaced. Always act quickly if and when you see water on your floors so you won’t have to worry about it soaking into the subfloor and causing more costly damage.
How Do You Get Moisture Out Of A Subfloor?
If you think there could be moisture in your subfloor from a leak or flood, you may be worried about what the moisture will do if it’s there for a long time. There are a few ways to remove the moisture from your subfloor, so it doesn’t become damaged.
In general, ventilation is key. If you plan to use natural ventilation, always know that this only works if the humidity outside is at an average level. If you live in a humid area, you probably need to use other measures like a dehumidifier or your AC.
Here are a few measures to get the moisture out of a subfloor:
● Remove Moisture From A Subfloor: Air Dry
While this could be a slow process, you can let the room air dry without other measures. It will likely take some time for all the moisture to leave the subfloor, and it could have already caused damage by the time it dries.
● Remove Moisture From A Subfloor: Open The Windows
You can help move the air around in your room by opening the windows. With air circulation, your subfloors are more likely to dry faster. Since you need to work fast, anything that can help move the moisture out is a great option. Opening the windows will pull out any moisture and help it dry faster.
● Remove Moisture From A Subfloor: Fans
Fans can also help dry out a room or a subfloor. If you are able to set up commercial fans, they may work even faster. Personal fans can also work if that’s all you have. The fans will help move air around in the room and reduce the chance of the subfloor getting so wet that it starts to swell or allow mold to grow.
● Remove Moisture From A Subfloor: Towels
As long as you are able to change them out as needed, you can use towels to help pull out the moisture that may be in the subfloor. Once the towels are saturated, you should remove them and put down dry ones to continue to absorb the water.
● Remove Moisture From A Subfloor: Dehumidifier or your air conditioner
A great way to quickly remove moisture from your subfloor is using a dehumidifier or your air conditioner system. This is particularly true if you live in an area where the humidity outside is high.
You can use a residential dehumidifier, but I always recommend renting a commercial dehumidifier. They can remove a lot more water per hour than a residential dehumidifier.
A dehumidifier pulls in the moisture from the air and dries it out to release dry air back into the room. When used with a fan, this can be highly effective at drying out the drywall quickly.