One of the most common areas in a home where mould can be found is the basement due to its high moisture content.  Mould thrives in a moist environment.  The basement is an ideal spot as more often than not, it’s damp and humid, sees little or no light, and has very little ventilation.

basement mould

What causes mould in basements?


One of the biggest causes of mould in the basement is flooding. If a house is flooded, water runs down to the basement and stays there long after the other rooms have dried.


Leaking pipes in the basement or in nearby rooms may also lead to basement mould growth. Water in the ground can also find its way into the basement through cracks in the walls, especially if the ground is sloped towards your foundation.


High humidity plus the often cold temperatures in the basement produces a lot of condensation. Condensation collects on cold metal pipes, cold concrete basement floors (even if there is carpet on top) and on walls.

basement flooding

Where does basement mould grow?

 Mould loves to grow on basement building materials including drywall, wood and insulation. Some of the most common places where mould grows in the basement are:

  • Walls
  • Wall cavities
  • Wooden building frames
  • Ceiling
  • Floor
  • Insulation
  • Storage boxes
  • Furniture
  • Pipes
  • Ducts and vents

Signs of Mould in Basement

One of the clearest signs that you have mould in your basement is the smell. Because of the stagnant air in the basement, odours build up and become very noticeable. Don’t ignore a musty or mouldy smell in the basement as it probably means you have a basement mould problem.
Finding Mould in Basement

When looking for mould in the basement you should begin by trying to find any signs of moisture. Areas where there are signs of water damage, leaks or condensation are likely spots for mould grow.

Can mould spread throughout my home?

Even if you only have mould in the basement or crawl space, its spores will rise throughout the home. The reason for this is called the “Stack Effect”. The stack effect is what causes warm air to rise in the home and exit through the upper levels and attic. As this happens, a vacuum is created on the lower level which draws air upwards from the basement and crawl space. Anything in that air, including mould spores, humidity, dust mites, and odours, will be drawn into the main area of the home.  Needless to say, mould remediation is absolutely necessary and the sooner you get rid of it, the better.

stack effect

How to get rid of mould

Cleaning and removing crawl space and basement mould with bleach or any other common household product is only a temporary solution. Mould remediation of this type can eliminate it in the short term, but unless the reason that it was there in the first place is not eliminated, there’s nothing stopping it from returning.

Until you have addressed the root cause of where the mould is coming from, here are some common household products that you can use to temporarily clean surface mould: Bleach, Borax, Vinegar, Ammonia, Hydrogen peroxide, Detergent, Baking soda, and Tea tree oil.

Other best in the market commercial mould cleaners include:

RMR-86 Instant Mold & Mildew Stain Remover Spray & Forget Revolutionary Mold Remover
ZEP Mold Stain and Mildew Stain Remover Skylarlife Home Mold & Mildew Remover
Wet and Forget Mold Remover Clorox Tilex Mold & Mildew Remover
Concrobium Mold Control Household Cleaner Home Armour Mold & Mildew Remover
EcoClean Solutions Mold & Mildew Remover SIamens International Concrobium Mold Spray

These products can be found at your local hardware store or can be purchased online.

To reiterate, you need to find the source of where the mould is coming from and fix that first.  Once you’ve addressed the source, mould remediation can occur.  We recommend that you hire a professional mould remediation service to do this if you have a substantial amount of mould.  You can easily find mould remediation professionals by searching online for “local mould remediation companies” or “flood restoration companies near me”.


What is the average cost to have the mould removed?

Typical mould remediation of areas such as crawlspaces in the home can cost between $500 and $4,000 depending on the extent of the mould and the type. Most homeowners can expect to pay around $2,000 for remediation of areas such as crawlspaces, attics, or basements where mould is most commonly found.

How to prevent mould from developing in the basement

Since mould thrives in a moist environment, try to keep your basement at 55% humidity or less.

Here are some additional tips to prevent mould growth in your basement:

  • Never allow water to accumulate near the basement. Make sure that the ground outside your home slopes away.
  • Avoid having carpets in your basement.
  • Keep condensation in your basement to a minimum. Wrap cold surfaces like basement pipes with insulation. To make windows air tight, use a sealant around them.
  • Increase the temperature in your basement.
  • Install a dehumidifier. Control dampness by promoting air circulation in your basement. When possible, keep the basement windows open or open the doors leading to the basement.
  • Run a fan for one to two hours daily in the basement.
  • If you don’t already have one, install a sump pump and/or a perimeter drain.
  • Keep the basement clean and free of clutter. Discard any badly damaged or extra materials stored in basement. This improves air circulation and ventilation. Also clean your basement regularly. Don’t allow dust to settle there, as dust attracts mould.
  • Avoid wood flooring in your basement.
  • Never store wooden materials, fabrics, paper, books or any materials that provide food for mould in your basement. If you do have such items, store them in plastic tubs.

If you have discovered mould in your attic, click here to learn more.