New house under construction with on stacker wooden material door molding trim

9 Signs of Mold Under Hardwood Floors

When you catch mold at its beginning stages, you can have it professionally abated and put an end to it before it does much damage. The longer mold grows, the greater the damage it does. How do you know that your house has developed mold? It can grow in the walls and under the floor, and dang it, you’re lacking those x-ray eyes that KISS sings about.

Mold doesn’t subtly hide. Even when it grows under the floor or in a wall, it lets you know it invaded. Mold stinks and wreaks damage to wood, creating a visible difference in its appearance and consistency. Let’s consider the nine signs that your home has a mold problem.

If you notice any of these signs, phone a mold abatement professional. They’ll come to examine the flooring by pulling up a plank to check the underside of it. They may also look inside your walls. Once they know it’s there and what kind of mold has developed, you can have them remove and abate it.

  • A musty odor in the room
A musty smell signals growing mold, like a long-closed room with no air circulating. You've probably caught it early if you only smell it but can’t see any visible signs.

  • Discolored floorboards
When it grows on bread, mold usually takes on a blue hue, but not all mold grows blue. More than 100,000 forms of mold exist worldwide, and like the latest fashions, it also comes in black, green, greenish-black, white, brown, yellow, and orange. As it develops, mold takes over the wood and erodes it. Even if you clean it off with bleach, you may notice changes in the wood and its grain.

  • Standing water
You may not notice standing water until the mold begins to grow and draws you to its patch with the smell. Mold doesn’t need flood water to develop. Something as simple as overwatering your plants can cause water to spill out of the planter’s tray and onto your floorboards. As it permeates through the floorboards repeatedly from the leaky or overflowing planter, mold develops under your floor.

  • Water Stains
The water may dry, but the water stains wood. When it does this, the wood becomes lighter colored, as if you spilled bleach. Sometimes, porous wood becomes darker when water permeates it. Either way, if you see water stains and smell mustiness, you need a pro to check for mold under the floorboards.

  • Texture changes in the wood
Mold does many types of damage. Your floor may become dirty, dusty, fuzzy, or powdery as it grows. If you sweep or mop, then notice that after a few days, the same texture appears again; you probably have mold. Put on plastic work gloves and a face mask, preferably a respirator, and poke the wood. Does it feel spongy? Does it feel oddly textured, as if the smoothness gave way to crevices or threading? If you answer yes, you probably have mold growing on your floors.

  • Warped floorboards
Mold causes three main types of structural damage if not removed quickly. It causes warping, a condition caused when water spills on the floor and evaporates, but not before mold grows. The fungi cling to the underside of the hardwood, over time causing the planks to peel away from their prior positions. The spaces between the hardwood planks grow so you can see the subfloor between them. If the mold gets to the subfloor, too, its wood starts to expand.

  • Cupped floorboards
Water must penetrate wood flooring for an extended period to cause mold growth that leads to cupping, a condition in which the wood rises at the edge of the plank. This makes the floorboard appear wavy. Mold attacks the fibers in wood, weakening them. The attack starts the process of wood rot.

  • Crowning floorboards
Water exposure followed by mold growth can also cause crowning, a condition in which the middle area of a hardwood floor rises. This buckling can develop after you fix a cupping situation by sanding the floor if the moisture and mold reach the floor’s base.

  • Insects Infestations
Carpenter ants and termites love wet wood, so if you notice an infestation of either, have your home checked for mold, too. Either of these insects on your floor means a likely mold problem.

What Kind of Mold Infected the Floor?

While you must treat any mold found, immediately phone a professional if you spot black or greenish-black mold in your home. Your home probably has Stachybotrys chartarum growing in it, and that dangerous type of mold releases mycotoxins that can cause serious health issues or death. Other types may cause health issues like allergy attacks or exacerbate asthma. Here’s a quick guide on mold colors:

  • White – the most common species that grows on wood; typically, a variant of Penicillium, Cladosporium, or Aspergillus
  • Black – dangerous Alternaria and Cladosporium varieties
  • Green or Bluish green – Penicillium, Cladosporium, or Aspergillus; one variety of this provides the essential ingredient of penicillin
  • Greenish black – Stachybotrys chartarum appears slimy
  • Brown – Aureobasidium pullulans or Pithomyces chartarum     
  • Yellow – Serpula lacrymans or Epicoccum nigrum
  • Orange – Serpula lacrymans' variants

Your abatement professional will use a different approach to treating each of these varieties of mold.

Replacing Damaged Flooring

Sometimes, you don’t catch the mold’s development early enough to save your floors. Shop From the Forest for natural hardwood flooring or laminate that looks like real wood. Let us help you rebuild after mold damage.

Leave a comment

Please note, comments need to be approved before they are published.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.