Improper Installation

Proper installation thwarts a lot of moisture problems that could occur with your hardwood floors. This involves installing the right subfloor and protecting it with an adequate underlayment. Cement floors require a moisture barrier so that the condensation produced from temperature changes doesn’t seep into the hardwood. 

How to Fix It: Unfortunately, the best way to remedy an installation problem is to have the existing flooring removed and reinstalled. You could repair a small area if the moisture problem is not widespread. However, without installing the floors properly, you will probably continue to have issues down the road.

Make sure that the hardwood floors are properly sealed before you walk on them. You should also acclimate the wood to your indoor environment before installing it. This allows it to breathe, adapting to the humidity levels in your space and letting go of excess moisture before it gets trapped beneath the floorboards.

Using too Much Water When You Mop

Liquids should always be cleaned off of hardwood surfaces right away. If you mop the floors using puddles of water, you risk the liquid leaking into the cracks and creating moisture problems under the hardwood floors.

How to Fix It: Sweep, dust or dry-mop your hardwood floors regularly. Doing this daily prevents the need for deep cleaning. If you must use water to remove residue or grime from your floors, use a barely damp cloth, and dry your floors after you’re done.

Leaking Appliances

Is your washing machine or refrigerator leaking without your knowledge? If appliances are losing water in hidden areas, the liquid could pool beneath the floor. The hardwood underneath could buckle, but you won’t see it. 

Some signs that you have a hidden water leak from an appliance include the following:

  • Your refrigerator keeps freezing
  • Your water bill is higher for no obvious reason
  • Walls and ceilings in lower levels have water stains
  • You notice a musty smell around your appliances.

How to Fix It: Identify and repair the source of theleak. Before replacing your appliance, however, you’ll need to inspect the flooring and subfloor. Remove decayed boards, treat the area for moisture, and install the new flooring properly.

Water Intrusion

If your roof, exterior walls or foundation is compromised, you could develop moisture under hardwood floors. Water can flow into the tiniest cracks. If the water volume is high or consistent enough to prevent the material from drying out, it could rot and warp your flooring.

How to Fix It: Call the appropriate professional to identify and repair the problem. Moisture in the crawlspace can also make its way under your hardwood floors. Some tips for keeping water at bay include adding gutters to your roof, having your crawlspace inspected and using the right vapor barriers, dehumidifiers and insulation.

Incontinent Pets

Unfortunately, pets can have accidents inside. Moreover, you may not notice until you start to smell urine. By this time, the moisture may have seeped underneath the floorboards. If your pet has accidents in the same spot repeatedly, the hardwood will get damaged. The subfloor might also absorb the liquid.

How to Fix It: It’s not easy to get the smell of pet urine out of any material, including hardwood. The best course of action is to replace any affected pieces of flooring. Restrict your pet to parts of the home with waterproof floors, such as tile or vinyl, when you’re not around. Clean up accidents as soon as you see them happen.

Signs of Moisture Under Hardwood Floors

As wood absorbs water, it swells. Soaking a piece of wood in a bucket of water would cause it to expand uniformly. But If your hardwood floor is only picking up water from its underside, it will only expand on that surface. 


The material’s uneven expansion leads to cupping. The edges of the planks will turn upward, creating a u-shaped profile. The floors will begin to feel uneven, and the raised surfaces will be vulnerable to more wear and tear than the valleys. As the wood swells, it can shift, creating gaps between the boards.

Water Droplets

Have you noticed beads of water forming on top of your floors, but you can’t find a source? The wood may be holding onto moisture that it’s absorbing from below. Condensation on your floors is also a sign that the indoor humidity is too high. Use your air conditioner or a dehumidifier to keep humidity levels below 55%.


If parts of the floor feel weak or soft, they might be rotting. Moisture beneath the floorboards almost always leads to decay. The rot can transfer to other floorboards and affect the structural integrity of your home. If your floors are rotting, you probably have moisture damage to the subfloor and underlayment too. Hire a professional to remediate the moisture problem and repair the flooring.

Pest Problems

Many pests, such as ants, cockroaches, silverfish and earwigs, are attracted to moisture. If they’re infesting your home, you might want to have your flooring inspected for moisture under hardwood floors. Humid environments are also magnets for termites. Prevent this from becoming a bigger problem by identifying the source.

Musty Odors

Musty, mildewy odors are almost always a sign of a moisture problem somewhere in your home. Dampness promotes the growth of bacteria and fungus, which make your home smell bad. It often takes a professional to remediate the issue and prevent these organisms from spreading.

Squeaking Floorboards

You might think that it’s normal for floorboards to squeak. However, properly installed hardwood shouldn’t make noise when you step on it. Plus, a new squeak is a sign that something has changed.

Creaking floorboards don’t always indicate that you have a moisture problem. Your subfloor could be uneven, or the joists could be sagging. Still, it’s a good idea to rule out moisture under hardwood floors if you’re noticing strange noises underfoot.


Water stains that come from above will usually create rings or discolored patches on the surface of your floorboards. But if there’s moisture under your hardwood floors, the staining will look different. You might notice darkness along the edges of the room or between the planks. 

Check for Moisture

If you’re not sure whether your flooring is damaged from water or another issue, you can conduct a moisture test. Use a moisture testing meter in various locations where you spot damage. High readings could indicate that you have moisture under hardwood floors and it’s time to call in the professionals.