Basement Humidity: Why It Happens and What to Do

How do you know if you have a problem with humidity in your basement? Touch, look and smell. Feeling or smelling moisture when going down to the basement or seeing some water-affected areas are often signs that the humidity is too high. Such a situation is not to be taken lightly since it can cause significant damage to your home and your health. Fortunately, there are solutions to fix it!

Before undertaking anything, it is important to know the risks associated with moisture in a basement, the causes, as well as how to get rid of it.

The consequences of a humid basement

As the warm air always rises the air of your basement travels from floor to floor, up to upper level rooms. This is called the chimney effect. Thus, the air of a wet basement that is touched by contaminants, such as mold, will also be found on the upper floors of your home. The list of negative effects directly related to high basement humidity is quite long. Here is what to look out for:

  • Curvy hardwood floors
  • Rubbing doors (due to swelling)
  • Carpets or other damp fabrics giving off odors
  • More intense presence of dust mites (most important indoor allergen)
  • Condensation, rots, and molds which, thanks to the heat, go up to your loft and settle there
  • Frost, condensation, and mold inside the windows when the temperature drops below zero
  • Increased heating and cooling bills (moist air = more difficult to heat and cool)
  • Aggravation of allergies and asthma
  • Etc.

To protect your own health and that of your loved ones, don’t wait for such a situation and attack the problem directly at the source. Remember to decontaminate your basement if any of these problems arise.

water infiltration humid basement

Causes of moisture in a basement

There are four main reasons why a basement is humid or wet:

  1. Infiltration of groundwater.
  2. Capillary action (when your concrete blocks absorb water and become like sponges).
  3. A problem related to the water vapor that runs through your walls.
  4. Air infiltration in your basement, which lets in as much water as air.

How to prevent water infiltration in a basement

If you want to prevent water infiltration from crossing your foundation and making your way to the inside of your property, there are two preventative practices to follow:

  1. From the outside, apply a waterproof coating or membrane to the basement walls.
    Note: basement waterproofing is not a DIY job. It is a difficult and complex project that should only be supported by professionals in this field. These specialized contractors have the knowledge and skills to waterproof a basement with specialized equipment for this type of task. Our Renovation Advisors can provide with no fees, Verified Contractor recommendations to execute the work according to the rules of the art.
  2. Install a French drain around the foundation, which will discharge excess water away from your home. You can look at our article about French drain costs to get a better idea of the price. Before the 1970s, it wasn’t mandatory to have a French drain around one’s house. If the slope from your house is negative and your house was built before the 1970s, it is at risk of water accumulation. It is possible that your home has water infiltration through its foundations. It would, therefore, be important to correct the situation quickly.

That said, even if you have a French drain, it’s worth noting that its average life is estimated at around 20-25 years. After this time, it may be that it’s clogged with dirt and mud or pierced by branches and that it no longer rejects water as it did in its early years. It’s also possible to level the ground around your house by adding soil or clay to raise the slope of your home and reduce the risk of infiltration.

To learn more, read our article: “Water Infiltration: Preventing your home from damages“.

mold in a humid basement

How to reduce humidity in a basement

Despite all the efforts made, such as the installation of a French drain, the waterproofing of your foundation or the repair of your foundation cracks, it’s possible that the humidity continues to persist in your basement. In these cases, it can also be poor insulation or a crack letting in the outside air that you do not see. In this case, it would be important to consider adding a dehumidifier. However, simple dehumidifiers that can be found in a hardware store are not powerful enough to remove moisture properly. This is why you’ll need a professional system that will be able effectively to remove excess moisture.

Your dehumidifier must have an integrated water drainage system. If it doesn’t, as soon as the tank is full, you’ll have to empty it. A dehumidifier tank can fill up after 12 hours before turning off. In a case where the humidity is high, with a low-end dehumidifier you have to empty it several times a day. With an integrated system, the work is done alone throughout the year, without the risk of machine shutdown! In addition, these systems don’t run on a timer, but rather according to the humidity level in the air. Thus, it only starts when needed.

Basement Humidity

Are your foundation walls cracked?

It’s not always easy to see potential cracks all the way up inside your walls. If your basement is not finished with gypsum, you have the benefit of seeing from the inside if cracks are present on your foundations. Foundation cracks are a source of infiltration (water and air) and thus directly related to the increase of the humidity level in your basement. The repair of foundation cracks is therefore essential even before thinking about finishing your basement.

If you’re not a homeowner, but rent an apartment or own a condo you can read more about foundation cracks in our article “Foundation cracks in your building foundation“.

foundation cracks in concrete

How to treat damp walls in a basement

Whether your foundation is in poured concrete or concrete blocks, with the weather and humidity in a basement that is not completely renovated, it is possible that your walls are stained. What can you do to correct the situation?

First, do not finish a basement until the source of the moisture or infiltration problem has been corrected. This will not improve your basement and will instead create an ideal environment for mold growth. Once the problem is resolved, you can then consider a complete finishing and insulation solution, tailored to your needs.

If you do not want to finish your basement, there are several types of insulation boards that can be affixed directly to your foundation walls. They will not have the same finish, but they will help make your basement more isolated and more attractive, without having to pay a large amount. Zen Wall panels are an example.

gyps walls

Can a basement humidity problem have an impact on the sale of your home?

You guessed it – a potential buyer usually expects to buy a healthy home with a dry basement. They do not want to have to deal with problems arising from a humid basement.

A basement that isn’t completed or renovated, but also has a moisture problem, even benign, will have an impact on the resale value of your home. In general, an impairment loss of 10% of the total value of the house is calculated. For example, for a house of $400,000, you will lose about $40,000. This is the minimum loss threshold because it doesn’t include damage or the cost of repairs and renovations. If the buyer has to change a French drain, repair cracks, redo finishes and the floor, this will add to your losses as a seller.

Before investing in a basement renovation

If you’re thinking about finishing your basement, know that there are plenty of benefits in doing so. In addition to being a great way to earn additional living space, you’ll get a very interesting return on investment (50 to 75%). However, you can’t think of doing so until you have solved the causes of the humidity in your basement. The way you choose to layout your basement will not solve moisture problems. It can cost you up to $40,000, or sometimes more, to insulate and complete the finish of your basement.

Note: it’s best to avoid wood flooring in the basement. With moisture usually higher in this space than elsewhere in the house, wood would swell, and if there is a seepage or water damage due to a sump pump problem, the wood would rise. A floating floor solution would be better suited to achieve a wood effect without the disadvantages.

Installing new floor

Learn more about the costs of a basement finish by taking a look at our basement renovation cost article. You’ll find the different costs for insulation, flooring, walls, divisions and more.

Would you like get inspired by real basement renovation projects? Check out basement ideas on our Reno-Inspiration page. With each project, you’ll find details along with their price tag. It’s a great way to get some good ideas while thinking about your budget and the type of project you want to do.

Invest in a dry basement or endure a wet basement?

Fixing the problems of a wet basement is not the most exciting project, it’s true. But if you push the problem too long, your health may suffer … and your wallet too! The more important problems will cost more to correct. It is always more economical to solve the problem when it is small. In addition, with a basement in good condition, you will enjoy the space for many years.

Need to speak to an expert or ready to receive quotes with no fees?

If you’re ready to get started with your basement renovation, then you’ll need some help looking for some basement contractors.

Call us or fill out our form to speak to one of our Renovation Advisors. They can help you with your project with no fees, by rallying up three Verified Contractors to compete on your project. You’ll get fairly priced quotes, all at no cost, no obligation to you!

Happy Renovations Start Here!

Marilena Tricarico has been a key figure in the interior design world for over 15 years. Her expertise and designs have been featured on the hit TV show Décore ta Vie for 10 years. Today, she shares her knowledge of the renovation industry with RenoAssistance as a video content producer and host.