A damp basement can lead to mold growth, structural damage, and foul odors. In this article, we’ll explore the causes of wet basements and solutions to keep the area dry and healthy. Plumbing and heating expert Richard Trethewey demonstrates methods for controlling basement moisture to This Old House host, Kevin O’Connor.
Understanding the Scope of Basement Moisture Problems
Basement moisture issues are more common than you might think. Trethewey notes that about 40% of homes in the U.S. have basements and 60% of those experience moisture issues.
Common Causes of Wet Basements
Many factors can contribute to a damp basement, including improper grading, poor gutter and downspout systems, groundwater seepage, and condensation from high humidity levels. Sometimes, multiple causes can contribute to the issue.
The Dangers of a Damp Basement
A wet basement can pose risks to you and your family. These include mold growth, structural damage, and poor indoor air quality. These problems can impact your home’s livability and resale value.
Solutions for Controlling Basement Moisture
Several exterior and interior solutions can help control basement moisture and address water drainage and sealant issues.
Improving Exterior Drainage
Proper exterior drainage prevents water from reaching the foundation, helping to keep basements dry and reducing potential damage. One of the first steps in addressing basement moisture is to manage water outside the home:
- Extend downspouts: Make sure water from the roof is directed at least five feet away from the foundation.
- Regrade the landscape: Slope the ground away from the house to prevent water from pooling near the foundation.
- Install French drains: These underground drainage systems redirect water away from the foundation.
Sealing Foundation Walls
Sealing solutions focus on creating a watertight envelope around the basement, preventing exterior moisture from entering your home. For moisture coming through the foundation itself, sealing can often resolve this issue:
- Apply hydraulic cement: This quick-setting material plugs active leaks in concrete or masonry walls.
- Use epoxy-based sealants: These create a waterproof barrier on foundation walls.
- Install plastic sheeting: This acts as a vapor barrier when applied to foundation walls.
Implementing a Subfloor System
To manage moisture coming up through the concrete slab, install a floating subfloor for better air circulation and use vapor barriers like plastic sheeting under the subfloor to provide more protection against ground moisture. Subfloor systems protect the basement flooring and promote healthy air circulation, reducing the chances of mold growth. These systems are best in areas with high water levels or poor soil drainage.
Managing Basement Humidity
Controlling humidity produces a dry basement, as explained by Trethewey, who shares that the ideal humidity level for buildings is around 30%.
Understanding Relative Humidity
Relative humidity (RH) is the amount of moisture in the air compared to what the air can hold at that temperature. For example, 100% RH is saturated with moisture and would be visible as steam or fog, while 0% RH is extremely dry air, commonly in desert climates. This makes 25% to 30% RH the ideal range for comfort and preventing mold growth.
Using Dehumidifiers
Dehumidifiers are often the best solution for controlling basement humidity. Dehumidifiers draw in moist air, cool it to condense the moisture, and reheat it before releasing it back into the room. Residential units can remove up to 50 pints of moisture daily, while built-in systems can handle 100 pints or more.
Some features to look for when purchasing a dehumidifier include adjustable settings, automatic shut-off, a continuous drain option, and a built-in pump for units that need to drain upwards. Modern dehumidifiers often come with built-in pumps, allowing them to drain into sinks or other elevated disposal points up to 16 feet away.
Additional Basement Moisture Control Measures
Proper Ventilation
Improving air circulation can help reduce moisture levels. To do this, install exhaust fans in bathrooms and laundry rooms, use window fans for better air movement, or purchase a whole-house ventilation system.
Proper ventilation reduces moisture buildup, making maintaining a dry and comfortable basement easier. Installing and maintaining these systems can improve air quality and reduce moisture-related issues.
Insulation Improvements
Proper insulation can prevent condensation. You should insulate cold water pipes to prevent sweating, insulate your basement walls and ceiling, and use vapor barriers with insulation. All of these can reduce moisture-filled air and avoid condensation for a drier basement.
Regular Maintenance
Consistent upkeep can prevent many moisture issues. Regularly clean gutters and downspouts, inspect and repair foundation cracks, and monitor indoor humidity levels with a hygrometer.
Regular maintenance practices keep your home’s moisture management systems in good condition. Addressing any issues reduces the risk of more significant problems down the line.
Choosing the Right Moisture Control Solutions For Your Basement
Consult with professionals to assess your basement situation, develop a plan, and avoid potential issues.
Assessing the Situation
Begin by identifying the sources of moisture by observing exterior conditions for improper grading, inspecting the interior foundation walls and floors for cracks or signs of water, and measuring humidity levels using a hygrometer. An accurate assessment of your basement and exterior pinpoints problem areas and guides you to the right moisture control solution.
Developing a Comprehensive Plan
A multi-step plan is often necessary to achieve the best, longest-lasting results. Combine exterior and interior moisture control measures, prioritize action based on the severity of the issue, and plan for regular maintenance to keep your basement in good condition.
