How Do I Know If My Floor Is Rotting Under the Surface?

Rot under the surface usually appears as a soft, spongy area when you walk across it. Press down with your foot or a heavy object. If the floor gives more than usual, the subfloor beneath may be weakened by moisture. You might also notice that the floor feels springy or uneven, which can indicate that the support below is no longer solid.

Dark circular stains or a warped, buckling appearance are also warning signs. A musty, earthy smell often comes from trapped moisture and decaying wood. If you see any of these, check the area closely and feel for dampness. Look for discoloration along seams or near walls, where moisture tends to collect.

• Floor feels soft or bouncy underfoot
• Visible dark spots or discoloration
• Warped, cupped, or buckled planks
• Musty or moldy odor in the room
• Mold growth along baseboards or seams
• Squeaking that worsens over time

You can do a simple test with a plastic sheet. Tape a square of plastic to the floor and leave it for 24 hours. If moisture collects underneath, the wood is releasing trapped water, which is a sign of a problem. This test is easy to do and can give you a good indication of whether moisture is present.

A moisture meter, available at hardware stores, gives a more exact reading. Insert the pins into the wood and compare the number to the dry baseline. High readings mean the subfloor is still wet and needs attention. You can also use a screwdriver to probe the wood gently; if it sinks in easily, the wood may be soft and rotted.

If rot has spread, the damaged sections of flooring and subfloor usually need to be removed and replaced. This involves cutting out the soft wood, drying the area, and installing new material. The work often includes checking the joists and supports underneath to ensure they are still sound. In some cases, only a small patch is needed, but in others, a larger section may require replacement.

The cost depends on the size of the area, the type of flooring, and how much subfloor needs replacing. Typically, you might spend a few hundred to a few thousand dollars. A professional can give you a clear picture after an inspection. They can also explain the different material options and what each involves in terms of maintenance and durability.