Carpet Roll

October 30, 2020

Is There Mould Under My Flooring?

Hardwood floors are majestic, beautiful, and fashionable.

The age-old flooring material makes for a warm underfoot and brings the aesthetics of nature into your home.

Beneath the beauty and splendour, hardwood floors require proper care to increase their lifespan and reduce susceptibility to moisture.

Too much water and moisture cause the wood to rot and encourages a mould infestation, which is detrimental to your floor and health as well.

But how do I know if there’s mould under your flooring?

Here are a few signs that your home could be harbouring deadly mould. 

3 Signs of Mould Under the Flooring

For the most part, the sight of ghastly mould patches is the best way to confirm its presence. However, mould thrives in the dark, warm, and moist recessed areas of your home, such as under the floorboards. In such instances, these signs can help you confirm the presence of mould under the flooring.

1. Strange Musty Smells

If you encounter a strange pungent, musty, earthy smell in certain parts of the house, you might have a mould infestation.

The scent is reminiscent of decaying organic matter, hence unpleasant to your nose. Close examining the floor area with the strongest musty smell can reveal another sign of a mould infestation.

2. Discoloured Floorboards

Discoloured, distorted, and warped floorboards are a strong indicator that you have a mould problem. Mould often appears as discoloration, staining, or a fuzzy coloured growth on wooden floorboards.

In most cases, a mould infestation follows a simple flooding incident in the house. It could be a leaking sink, a backing toilet, or an overflowing tub. Depending on the level of infestation, a mould presence might be accompanied by damaged floorboards.

3. Visual Confirmation

If you notice a discoloured or water damaged section of your flooring, you should peak under those floorboards. Remove a small section of the floor and check underneath the boards for mould.

What Does Mould Look Like?

Depending on the species, mould can take on different texture and form. Most commons species have a fuzzy, rough, or velvety appearance and can be white, yellow, black, green, or blue. Sometimes it can look like a stain or discolouration on a surface.

Removing Mould from Under Your Hardwood Floor

You need to act quickly once you confirm the presence of a mould infestation under your floorboards. As with any health problem, early intervention is advantageous when dealing with mould.

With early detection, you can quickly swing into action and stem the spread of the fungus to the rest of the house. Removing mould under a wooden floor entails peeling back the damaged floorboards and disposing of them properly.

You may need to order another batch of floorboards to replace the infested ones. While that might seem like overkill, it’s the best way to solve the problem.

Read our article on the types of wood-look flooring

Failing to replace the floorboards increases the chances of a re-infestation as the residual mould gets into other parts of the house. Before you know it, you could be dealing with a large-scale infestation that could endanger your health and wellbeing.

If the infestation only covers a small section of your hardwood floors, you can remove it yourself.

Items You’ll Need

  • Safety goggles and gloves
  • Plastic sheeting
  • Protective clothing
  • Garbage bags
  • Pry bar
  • 2 buckets
  • Scrubbing brush or a broom
  • Dehumidifier
  • Borax
  • Spray bottle
  • Disposable rags

Step by Step Process to Remove Mould from Under a Wooden Floor

  1. Clear the room. To do a thorough job, you need to declutter the space. Remove the uncontaminated items from the room, bag the infested items into garbage bags, and leave them outside. You can throw away the replaceable things and leave the others out in the sun.
  2. Seal the room. Seal the door leading from the room by hanging a plastic sheeting on the door. Open the windows to allow to improve air circulation in the room. You can also set up a fan and point it towards the open window.
  3. Remove the floorboard in the affected area. Pry the base wall trim to gain better access to the floorboards. Start from the edge of the room and remove the infested floorboards until you’ve uncovered all the mould. Expand the section to include an extra foot or two of uninfected wood as a safety precaution.
  4. Spray the exposed mould patches with water. A fine spray of water weighs down the mould’s spores and keeps them from flying about in the room.
  5. Carefully inspect the hardwood floorboards. You may clean and treat the boards in great shape, but be sure to discard all the discoloured, warped, or rotten boards. Sort through them and pile the undamaged floorboards to one side of the room.
  6. Treat the subfloor. In a large bucket, mix 1 cup borax with one gallon of water. If working with a small floor section, use a spray bottle to disperse the treatment. For widespread infestations, dip a broom into the borax solution and use it to swab the solution across the subfloor.
  7. Allow the borax solution to sit for 10 to 15 minutes. The treatment weighs down the mould while suppressing the release of spores. After the time lapses, scrub the subfloor with a brush to dislodge the mould.
  8. Reapply the borax solution and let it sit for another 10 minutes. Then scrub the subflooring a final time. By now, the borax solution has killed all the mould, and scrubbing removes all traces from the subflooring.
  9. Make a fresh batch of borax solution. Wet the floorboards with the treatment solution allow it to sit for ten minutes. After 10 minutes, wet the boards with the borax solution and scrub thoroughly. You may work over the affected area, so the excess solution falls on the subfloor. 
  10. Remove the dead mould. A HEPA vacuum removes the bulk of the dead mould quickly. You can also remove mould manually with a disposable rag dipped in the borax solution. Be sure to avoid oversaturating the subfloor or getting water under the adjacent hardwood floorboards. The excess moisture would only serve to start a new infestation cycle.
  11. Spray the subfloor and the salvaged floorboards with a fresh borax solution. Leave the treatment to dry for a day or two. You can use a dehumidifier to speed up the drying process. The borax residue prevents re-infestation by inhibiting mould growth.
  12. Replace the hardwood flooring. Get new floorboards to replace the damaged bits. Install both the fresh and clean floorboards and restore the hardwood floor. Treat the items removed from the room with a borax solution before returning them inside.

Safety Precautions

Always wear protective clothing and gloves before removing mould under the flooring.

Use a high-quality respirator or an OSHA-approved particle mask

You can use straight vinegar instead of a borax solution.

Don’t use bleach as mould treatment.

Call a mould remedial expert if you have any health concerns, or the mould infestation is too widespread under the floorboards.

 Mould is hazardous to your health, and you should take these safety precautions seriously when removing mould under the flooring.


What about stop worrying about mould under your flooring altogether? There are a number of flooring that are waterproof and less prone to mould growing underneath. View our range of vinyl flooring available for residential use and our commercial-grade vinyl for suited for commercial and health premises.