Why Is A Cool Basement Often Damp In The Summer? (Find Out Now!)

Jessica Allen
by Jessica Allen

In the winter, your basement is cool and dry, and you don’t even have to think about water damage. But once the summer months come around, it becomes damp and humid in your cool basement. Why does this happen, and what can you do to prevent it?

Signs of dampness in your basement include standing water, deteriorating wood or carpet, mold or mildew, and condensation. The source of your basement’s dampness could be groundwater or rain, ventilation with outside air, or interior factors. Ineffective grading, interior leaks, problematic gutters and downspouts, issues with drainage systems, foundation cracks, and condensation can all cause dampness.

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What Are Signs Of Dampness In The Basement?

There are several signs of dampness to look out for in your basement. Some signs are more obvious, while others are a bit more subtle.

Of course, standing water, water trickling out of the walls, and humid, damp air are clear signs of dampness. If you have concrete walls, examine the base of the concrete around the perimeter of the basement. If there appears to be a ring of dampness around the concrete’s base, that’s another sign.

You might also see condensation forming on the walls and floor. Stained or blistering walls and deteriorating wood or carpet are also signs of dampness and water damage. Another problematic sign is rotting joists, headers, and columns. If there’s a lot of dampness in the basement, you might also smell mold or mildew in the air.

Where Does Dampness In The Basement Come From?

Dampness comes from three main sources. They include interior sources like a downstairs shower or dryer, ventilation with humid air, and rain or groundwater.

Interior Moisture Sources

Interior moisture sources refer to dampness that originates from inside of your house. This could be a dryer venting into your basement. Another possibility is that you have a downstairs shower that could be causing humidity or moisture.

Another interior moisture source is a humidifier. Or, if you’ve recently laid concrete in your basement, that can also cause dampness.

Ventilation With Humid Air

Another source of dampness in the basement is ventilation with humid air that comes from outside. If you open your basement windows in the summertime for ventilation, you’re letting that warm, humid air into your cool basement. The moisture in the air then condenses, and your basement becomes damp.

Groundwater Or Rain

The third source of dampness in your basement is outside water that makes its way inside. This could be groundwater or rain. It’s essential to have proper gutters, downspouts, and grading in order to keep outside water out. Otherwise, you’re risking a lot of water damage as time goes on.

What Are The Main Causes Of Dampness In The Basement?

Now that we’ve covered the sources of dampness in the basement, let’s zero in on the specific causes.

Ineffective Grading

Poor grading is often the reason for rain and groundwater making their way into your basement. The ground around your house’s foundation should slope away from the house rather than towards it. This is frequently the result of improperly compacted dirt around the foundation of your house.

If the water drains in the wrong direction, it’ll start to accumulate against your foundation. It’ll eventually find its way into your basement and begin to cause water damage.

To fix ineffective grading, you’ll need to build up the dirt around the foundation of your home. Use the dirt to create a slope that aims away from your house. You can also hire a professional to fix the grading.

Interior Water Leak

If there’s dampness in your basement, then an interior leak could be to blame. Check the pipes and any appliances like dishwashers and washing machines. A sink, shower, or toilet could also be the culprit. To solve this issue, simply fix the leak (or hire a plumber to do it for you).

Problems With Gutters And Downspouts

The purpose of gutters and downspouts is to direct water away from your house’s foundation. When they’re missing or not working correctly, water can make its way into your basement.

If you don’t already have some, consider installing gutters to protect your home from water damage. If you do have gutters, be sure to clean them regularly. You can also add extenders to your downspouts to further direct the water away from your house’s foundation.

Issues With Drainage Systems

Subsurface drainage systems can require maintenance, and many homes don’t have them at all. Basements in many older homes weren’t built to be habitable spaces. Because of this, it wasn’t necessary to install a drainage system under the floor. Meanwhile, many newer houses with drainage systems can run into issues like clogged pipes and broken sump pumps.

This is one of the more challenging and expensive fixes for dampness in your basement. Adding a new subsurface drainage system is costly and labor-intensive. This type of waterproofing requires professionals and isn’t considered a DIY project. This is because the process involves digging up your flooring or the dirt around the foundation of your house.

Cracks In The Foundation

If your foundation has any cracks, it’s pretty much guaranteed that water will find its way in. But the way you handle cracks that are causing dampness depends on the specific cause.

If the floor joists aren’t connected to the foundation walls correctly, the walls can move and form cracks. Poor drainage in the soil can also lead to cracks due to water putting pressure on the walls. To fix cracks caused by water pressure, exterior drainage should do the trick. Structural problems leading to cracks will need to be fixed with proper footing and connections.


When warm, moist air comes into contact with the cool walls and floor of your basement, it forms condensation. Condensation is usually one of the simplest causes of dampness to fix.

Start by checking your dryer’s exhaust and draining your home’s central air conditioner. Check for any clogs or other issues that might keep them from flowing properly.

If you have a basement bathroom or kitchen, be sure to install an exhaust fan. The moisture that comes with showering and cooking can create condensation. An exhaust fan will take care of the steam so that it doesn’t condense and cause water damage.

Minor dampness in your basement can often be resolved by improved air circulation. You might want to add air conditioning vents or a fan if you don’t already have some in your basement.

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Related Questions

Why is a cool basement humid in the summer?

There are several reasons why a cool basement can become humid in the summer. First, if the soil around your foundation becomes oversaturated, wet foundation walls can cause humidity in the basement. Second, if your dryer is located in the basement, it can fill the basement with humid air.

Another cause of basement humidity is water underneath your foundation. Finally, humid air from outside can make its way inside through windows, doors, cracks, and gaps.

Is basement flooding covered by insurance?

If the water damage is sudden or accidental, it should be covered by your homeowners insurance. Your insurance will typically take care of the cost of cleanup after flooding.

Are basements required to have windows?

Finished basements must have at least one egress window. Otherwise, basements that have full-height foundation walls are required to have some type of window. This could be a ventilation window or an egress window.

Jessica Allen
Jessica Allen

With a lifelong passion for writing plus strong enthusiasm for home improvement and DIY projects, joining the team at Upgraded Home was an easy choice. Jessica Allen likes to share helpful information with current and aspiring homeowners. Aside from writing, Jessica loves doing yoga, playing the piano, and dabbling in graphic design.

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