When it comes to water damage on floors, there are three layers you should pay attention to: the top part of the floor, the body of the floor, and the subfloor. The top level refers to the surface and finish of your flooring. The body refers to the actual boards, while the subfloor is the layer underneath your floor boards. This third layer, or the subfloor, will be our focus in this article. 

Water damage from a flood, storm, or broken pipe can displace your operations and, if incorrectly handled, cause long-term structural damage to your building. Managing the property water damage insurance claim is complicated and time-consuming.

What is the Subfloor?

The subfloor is the invisible or hidden layer of your home’s floor. It refers to the concrete or plywood where your flooring is nailed or glued onto. Your subfloor could also be made from oriented strand board (OSB), high-performance panels, or other material.

Why is the Subfloor Important?

The subfloor has several functions. First, it serves as a level foundation or even flat surface on which you can install your flooring. It also holds up your walls. And, as it secures the joists of your crawl space or basement, it keeps your first floor in place. In other words, the subfloor provides extra support to your floor. 

Signs of Water Damage Under Floor

There are various things that can cause damage to your subfloor, including age or wear and tear and termite infestations. Another common problem most homeowners face when it comes to the subfloor is water exposure or water damage. 

As the subfloor is out of sight, you most likely have no idea what’s going on there. For the most part, if your flooring was properly installed and you have no leaks, you shouldn’t have to worry about this hidden floor layer. A well-constructed subfloor and one that’s properly installed can last for a long time. 

However, if the quality of the subfloor’s material is low or if the installation was not well done, then you might be facing a problem. Water can come from many sources and seep into your subfloor. When this happens, it becomes exposed to moisture which can lead to damage like rot.

If you suspect that your subfloor might have water damage, here are the signs you should look out for. 

Bouncing or squeaky floor

If you find that your floor is bouncy or more squeaky than normal, it might be time to schedule a subfloor inspection. If the squeaky noise is in just one particular area, then your inspector might recommend repairing that spot. But, if you find your floor squeaking in different areas, then you might be looking at replacing your entire subfloor. 

The squeaky noises arise from the separation of the subfloor and the joist. This happens when the nail that joins them together becomes loose. As there is now space between the subfloor and the joist, the subfloor rubs against the nails every time you step on it, resulting in the squeak. A visual cue of this problem is warping. 

Musty smell

Sometimes water damage can remain hidden, and in places such as the subfloor, it can be especially hard to spot. But, even if there are no visible signs, you might still be able to determine if the subfloor has water damage by sniffing for a musty smell. This is the kind of smell that persists even after you’ve done everything you can to get rid of it. 

In truth, if a musty smell is present, the damage is already done. This means, water has already seeped into your subfloor and now mold and mildew are growing there thanks to the ever-present moisture. The best thing you can do now is to determine where the damage is and fix it before it becomes a bigger problem. 

You should start looking for possible leaks in the usual places, such as the bathroom, kitchen, or laundry room. If the leak is hard to find, you can ask a professional to help you out. 

Cupping hardwood flooring

There are two possible causes for your hardwood floor to curl: improper installation or exposure to moisture. Running a moisture level check on your hardwood flooring will hit two birds with one stone. First, it can check if you have a moisture problem or if not, then there was a problem with the installation. 

If it’s the former, you’re looking at damage to the subfloor. This means water has seeped into the porous wood material, which makes it swell and curl or cup out of position. 

Uneven and sunken sections

In Memphis, Tennessee, a family living in a Hickory Hill apartment  found it hard to move around their bathroom on the second floor of the house. 

“The floor is caving in,” Adrian Solomon told Fox13 back in December 2023. “You step on it, you’re almost going to go through.” Solomon added that water has been dripping from that bathroom down to his kitchen and they’re afraid the sagging floor might give in at any moment. 

Visible sunken or uneven spots are classic signs of water damage under floor. And, the Solomon family is right to be worried for their safety because prolonged exposure to moisture will make the subfloor weak. If the floor feels spongy under your feet, you might be looking at rotting subfloor, which can be expensive to repair. 

How to Deal with Water Damage Under Floor

As soon as you find that your subfloor has been exposed to moisture, you should have them repaired as soon as possible. Otherwise, if your subfloor has been exposed to moisture for a long period, it might lead to extensive or irreparable damage. The water damage might result in the subfloor becoming weak and not able to support the floor or wall. 

And, replacement costs for subfloors don’t come cheap. Since it’s difficult to access and assess damage to the subfloor, you’ll need to pay for a general flooring inspection which can range between $100 and $400, according to Fixr.com

As for repairs, you could pay as low as $150 to as high as $2,000, but averages between $250 and $750 nationwide for professional subfloor repairs. The national average cost is $500 for a 150-square-foot section of plywood subflooring. 

While you can certainly do the repairs yourself, it might be worthwhile to ask the professionals for assistance. A professional contractor, for instance, has tons of experience than you so their team can do the job more quickly and thoroughly. They might also be able to point out other issues that you might have missed and help you solve or fix them.

Signs of Water Damage Under Floor

In conclusion, identifying signs of water damage under the floor, such as bouncing/squeaking, musty smells, cupping hardwood, and uneven/sunken spots, is crucial for prompt repairs. Neglecting subfloor damage can lead to costly replacements and structural issues. Professional assistance can ensure thorough assessments and efficient solutions for a safe and sturdy foundation.