Mold in the Basement: Preventive Measures and Tips

A moldy basement is something that every homeowner has had to deal with at some point. Although it is one of the most popular problems for homeowners, it is avoidable. Some of the common signs of the presence of mold are allergic reactions, headaches, or the nose getting stuffy. Unlike when caused by other illnesses, the symptoms will subside when you step out of the room or house.

The main cause of mold growth in the basement is the use of wall construction materials that are meant to be used above ground, underground. The use of concrete in the basement can also result in the growth of mold because of the long duration it takes to fully cure. The porous nature of the cement and the natural level of ventilation that occurs on the ground floor makes the basement more humid than other areas. If left unattended, moisture will continue to spread through the concrete and reach other parts of the house.

Although the right information about how to get rid of mold in basement can come in handy, other measures like proper insulation and choosing the right materials can save you a lot of money and stress in the future.

Mold in the Basement Preventive Measures and Tips

What Exactly Mold Is

Mold (also called mildew) is a kind of fungus that consists of tiny organisms that produce microscopic spores to multiply rapidly on damp surfaces. The pores tend to attach themselves to any type of surface, including shoes, clothing, and walls. Their tiny nature also makes them easily transferable through the wind. Mold thrives where there is warmth, humidity, and food in the form of any organic material, such as wood, wallpaper, fabric, and dust.

What Does Mold Look Like in the Basement

Mold in basement does not look intimidating or threatening, and it does not usually show up in the open spaces. It starts to grow in hidden areas such as inside walls, which means you may have to dig into those places to see the fungus.

Mold usually manifests itself in various colours, ranging from green to black. Some colours are more common in homes than others, with black being the least common. According to the Center for Disease Control, the most common types of mold in house are Penicillium, Cladosporium, Alternaria, and Aspergillus.

Despite the different appearances, the growth of all types of mold is driven by excess moisture in basement. They mostly attach to insulation material, carpets, upholstery, ceiling tiles, and paint. Any type of discoloration, especially those that appear in clusters, could indicate the presence of mold.

How House Mold Affects Your Health

Growing mold in basement isn’t just unattractive; it also poses a lot of health risks, with the level of threat varying with each mold type. In some cases, exposure can lead to mild allergic reactions, but at other times, it can result in compromised immunity.

How House Mold Affects Your Health

Mold can reach the body through inhalation, skin contact, or ingestion. It can cause an itchy or scratchy throat, watery eyes, runny nose, or asthma attacks. While these may not be life-threatening conditions, mold can be toxic to those who are hypersensitive. Those suffering from conditions causing respiratory distress are also likely to experience extreme effects of mold.

It is easy to distinguish the effects of mold from those of common illnesses. If the symptoms disappear when you leave the basement or house, you can suspect mold as the cause.

Even so, ignoring basement humidity and already existing mold is not a good idea. The longer the fungi spreads, the more your health is likely to be compromised, and the more you are likely to deal with expensive damages that will be too costly to repair. Getting rid of the mold permanently once it becomes dominant is also more challenging. Check to ensure there are no plumbing leaks, dampness around crawl spaces, or leaking roofs.

Real Reasons Behind Your Moldy Basement

All types of house molds need humidity and temperature to exist. As such, these elements must be present in our basement, but they can originate from different sources, namely:

1. Water leakages

Cracked cold joints: One of the signs of water intrusion and causes of white mold in the basement is cold joints on the areas where the floor meets the wall. It is common in sections that have cracks; however minimal they are. Such parts are also bound to crack because the flooring and the wall concrete are poured at varying times, which means their curing is different. Water will start to accumulate on one side of the point and eventually push its way to the other part, causing slight puddling or pooling of a lot of water.

Damaged foundation walls: Black mold in basement usually show up on the vertical foundation walls that are not installed correctly. Sealing and waterproofing of the walls should always be handled by professionals. Otherwise, they can allow water to seep through and create a conducive atmosphere for mold to grow. The holes do not have to be big for water to cause any damage.

Problematic slabs: Although this is not very common, water seeping through the middle of the slab can still cause mold to grow. This type of water leakage mostly occurs during the rainy season when the increased quantity of water causes too much pressure on the slabs. It is also rampant in houses where there is no sump pump to redirect water that finds its way into the foundation.

2. Humidity

Being below ground means the basement always has high humidity. Low temperatures down there reduce the air volume, but it does not interfere with the volume of moisture. This causes the moisture to occupy a larger part. It is important to note that the level of moisture does not change under such circumstances; it only increases in relation to air. The high humidity can be perfect for the growth of mold on drywall.

If, for example, the temperature in the basement reaches 68℉ and the relative humidity stays at 35%, mold will not grow because that is not a conducive atmosphere. However, if the temperature drops to 55℉ and humidity increases to 55%, mold will start to thrive. The problem is usually worse in areas likely to experience extreme winter conditions.

The poor ventilation present in most basements is another reason why mold is likely to grow there than in any other part of the house. High temperatures in the basement, together with proper insulation and ventilation can deter the growth of mold.

3. Presence of vapour

Vapour intrusion is common in basements built with concrete because of the porosity of the material. Large amounts of water can seep through cement unless curing and other factors like insulation are done properly. When the concrete is left uncovered, vapour can be absorbed into the air, which will eliminate mold-related problems.

However, the unattractive nature of bare concrete makes it the least used material in basements. Most people that have concrete cover it with carpets, which traps moisture. The more the quantity of the vapour increases, the more it gets harder to be absorbed into the air. As the carpet and floor retain more moisture, mold starts to grow. Sometimes mold growth is not visible, but it can be present on insulated and other interior surfaces.

The best way to differentiate mold growing because of water intrusion and that from vapour or humidity is by checking where it grows. If it is behind the sheetrock, it is caused by water intrusion, while that which grows on walls inside the room comes from condensation.

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How to Prevent and Get Rid of Mold Right Away

It is easier to ignore mold, but that is not a good idea. A small amount of the fungi is easy to remove with soap and water. However, if the fungi have extended to a larger area, you may need to hire professionals to handle it.

Bleach can also be efficient in removing small quantities of mold, but you will have to scrub those areas thoroughly to ensure you get all of it out. Trained mold remediation specialists are available to handle mold that spreads more than 10 feet and know how to get rid of mold in basement.

Preventive Measures

Some of the effective and simple preventive techniques you can try include:

  • Insulation

Insulation can go a long way in preventing condensations, especially when the temperatures outside exceed those inside the basement. The insulation material and the design used can both play a role in getting rid of mold in the basement because they determine how inhabitable the room becomes for the fungi. Using wood and fiberglass insulation on places that are likely to have a lot of moisture can lead to mold growing on them.

  • Installing footing drains

Footing drains can be installed inside the basement to capture water and channel it to the sump pump for proper drainage. These drains can be installed even after the construction of the house, and they will function properly.

The installation involves digging a small trench close to the outside walls and putting in a perforated drain pipe. The pipe will be connected to the sump pump to get rid of the water properly. The drain works with a dimple board, which catches water that is trying to reach the basement through the foundation and redirects it to the pipe. This is one of the most effective moisture prevention measures and one of the best ways of getting rid of mold in the basement.

  • Having adequate ventilation

Another important factor to look into when considering how to get rid of mold on walls is ventilation. Having windows down, there is not enough adequate ventilation because it is difficult to gauge the level of humidity outside. A good Heat Recovery Ventilator or An Energy Recovery Ventilator can come in handy with humidity control and make the house less conducive for fungi.

The ventilation systems in place should be taken care of and cleaned regularly, especially the filters. Regular inspection of the intake areas in the HVAC to check for signs of mold growth is also essential. If possible, the ventilation systems should also be placed in bathrooms, laundry rooms, and any other area where there is likely to be a lot of water usage.

  • Testing for radon

Radon is an odourless, colourless, and tasteless gas that is also radioactive. It is usually found in soil and rocks when uranium naturally breaks down. It travels through cracks in the foundation into the air. Increased amounts also indicate that the ventilation in the basement is not up to par. Testing for radon regularly will help you determine whether the conditions in the basement can promote the growth of mold.

There are technologically advanced devices that you can use to test under the slabs, the insulation, and inside the room. The presence of radon can pose a risk to your health, therefore you should implement measures that prevent the growth of mold, such as improving ventilation.

  • Reducing humidity

The relative humidity should always be between 35% to 50% to prevent the accumulation of allergens and bacteria that can cause health complications. A humidifier or air conditioner can be helpful if you cannot afford ERV or HRV. Make sure the level of humidity is enough to prevent chapped lips or cracking on furniture, but it is still low enough to prevent condensation.

When using a dehumidifier, make sure you empty the collected water regularly. You could also use a hydrometer to keep tabs on the humidity levels all the time.

  • Discarding water as soon as possible after a leak 

In case your area experiences floods or you get leaks in the house, eliminating the water as soon as possible is paramount. Improve the ventilation to ensure every affected area dries up properly. Do not cover any surface if it is still damp. If possible, remove all the damaged materials, including ceilings, carpet, drywall, and furniture. If there are items you would like to keep, bring a professional to clean and dry them thoroughly.

It may be tempting to paint over discoloured surfaces that water has made unattractive, but that is a big mistake you should not make. The paint will make the surface look better for a short while, but it will allow mold to grow and spread to other areas rapidly.

Useful basement Insulation Techniques

  • Mineral Wool + EPS + XPS

Expanded and extruded polystyrene and mineral wool are more rigid insulation panels that are cheaper choices compared to SPUF, but they also need to be handled with care.

This insulation method can increase the R-value and prevent the buildup of moisture by breaking the thermal bridge and increasing the temperature in the walls. By enhancing the stud wall temperature, the material also enhances insulation of wiring, which provides additional protection to the drywall.

Although EPS is pervious, the level of porosity is minimal, that it does not interfere with the material’s ability to provide insulation. Every two inches of EPS has 60-75 ng perms, a range that is allowed by building codes. Small amounts of moisture will still reach the walls, but it should pass through into the air, causing no damage.

EPS, XPS, and mineral wool can be used with polyethylene as a barrier, but it should be placed behind the stud. It can act as a radon gas barrier to improve indoor air quality. It could also help persuade building inspectors that are keen on vapour barriers.

Assembling the walls correctly

It is better to install rigid insulation boards directly against the concrete. You can use concrete nails or adhesive as wall framing continues. Stud walls should be placed at 24-inch intervals, and they should be pressed on the foams tightly.

You can then use mineral wool batts in the wall cavities because they are resistant to moisture. In case of exposure to water, they will dry quickly and maintain their R-value, which makes them superior to fiberglass. Drywall installation should be the next step, and it should be followed by the application of latex paint.

This type of insulation may seem extensive, but it offers a lot of value and better performance.

  • SPUF Method

Spray Polyurethane Foam or SPUF is usually sprayed directly on the walls, which makes it one of the best insulation materials. It spreads evenly to provide better protection than other insulation materials. The higher R-value per inch that the material has also adds to its benefits by serving as a moisture and air barrier.

On the downside, SPUF does not provide thermal protection. It also shrinks after application, which creates air gaps on the walls. It is also possible that some of the blowing agents that are used with the insulation material are detrimental to the environment.

Another potential disadvantage of this insulation method is that some contractors interfere with the chemical solution when using it. They may end up using less material with a high volume of the solution, which will not give the optimal protection needed. Such cases are very rare, but you still need to be careful about the installers you hire.

Insulation process

If you decide to do DIY insulation, you can start by creating stud walls at 24”, with the space between the studs and the concrete being at least an inch. The bottom layers should be shimmed up to avoid problems in case of flooding. Spray the foam on the concrete and be careful to leave enough space that will be the air and moisture barrier. Studs touching concrete can easily rot because of constant exposure to moisture.

Make sure the rim joists are insulated and cover the foam with drywall to prevent fire hazards. An extra vapour layer will not be necessary.

It is always better to hire a professional to do the installation to avoid a situation where SPUF creates a mess that makes the home inhabitable. If the spray lands on the wrong surface and hardens, it will be very difficult to get rid of.



The above measures will protect you and your loved ones, making your basement a safe and fun place to be. Always be on the lookout for condensation on walls, doors, and windows. Take the necessary measures to match the indoor temperatures with the outdoor ones to reduce the chances of condensation. Waterproofing outside the basement can also prevent a lot of moisture-related issues.

Watch out for common signs of mold, such as a musty smell, discolorations, and allergic reactions. Be careful with vapour barriers to ensure they do not cause the other materials to rot. In case you notice mold forming, clean it using bleach or soap or call a professional service provider near you to get rid of it permanently.