Finding moisture issues in a basement can be a major source of stress for a homeowner. Basements are meant to be dry. When moisture finds its way inside, dampness and subsequent mold can occur. This not only impacts the functionality of a basement, it can also pose significant health risks for the homes occupants. It is important to address moisture issues promptly; if they are ignored, these issues can compound over time, and grow more serious. When water penetrates the foundation walls, it can ultimately cause detrimental deterioration of materials.

With a variety of possible issues and circumstances, there are several different ways to handle basement moisture. Surface rain run-off is a major contributor to moisture issues in basements. Ground water issues can often be traced to ineffective gutters and downspouts, piping penetrations of foundation walls which were not fully sealed, and incorrectly placed irrigation systems. 

When a homeowner discovers moisture issues within their basement, they will first want to make sure all their gutters and downspouts are effectively routing water well away from the home. Further, the grade of soil should always slope away from the home. Basement windows can also be tested to ensure a watertight seal. In some cases, these tips may be enough to solve moisture problems.

If these tips are not enough to control the moisture entering a home, more aggressive waterproofing measures may be necessary. Below you will find information regarding the two main types of waterproofing – interior and exterior.

Without continued maintenance and upkeep of the home, issues can return. Below are listed some tips to control water seepage into your home:

+ Gutters should be checked to ensure they are functional. They should be inspected and cleaned at least twice a year. Downspouts should be repaired or replaced when cracked. Clean downspout boots twice a year.

+ Trim trees that are overhanging gutters. Keep bushes, trees, and other vegetation away from your foundation.

+ Reduce the amount of moisture used to clean steps and sidewalks. Clear away anything that will retain moisture from around your foundation, such as firewood piles.

+ Ensure the grade is sloping away from the foundation.

+ Ensure irrigation systems are operating correctly.

+ Check dehumidifiers, sump pumps, ventilation fans, and any water detection systems to ensure they are working properly. If needed, these can also be installed.

+ Check your crawl space for moisture. Install a polyethylene vapor barrier and/or ventilation if needed.

+ Ensure there is adequate ventilation in your home to account for moisture created, with fans in bathrooms, showers, and kitchens. Ensure there is adequate circulation in places like damp basements.

+ Check for condensation on pipes. Think about insulating pipes in places like unheated basements to avoid freezing, or water pipes which are subject to condensation.

+ Replace any older pipes and fixtures which are subject to leaking.


Interior waterproofing refers to a drainage system installed within the building. While the moisture is still allowed to penetrate the building, the system captures and controls that coming in from the walls and floor. The interior drain tile system, or French drain, is installed inside the footing at its lowest point, to carry water away. This type of waterproofing is often used when exterior waterproofing is impractical due to the increased cost or the accessibility of the foundation.



Quick installation

Water will still be permeating foundation walls


Basement is unusable during the installation

Repairs are often easier compared to exterior waterproofing

Requires some homeowner preparation: moving items within basement (shelving, cabinets, storage), as well as removing flooring materials, such as carpet

No exterior disruption


Can be performed year round


Exterior waterproofing involves excavating to the bottom of the foundation to install proper drainage, such as a trench or perimeter drain, at the exterior of the home. Walls are then treated with an exterior membrane to prevent water from re-entering. This process is effective when water is penetrating the foundation walls.



Little interior disruption

Expensive (more labor)

Little customer preparation

Disruptive (heavy equipment): Landscaping and pavement needs to be removed

Keeps moisture from entering the home

Takes 2-3x longer

Generally is thought to be the more effective option

Accessibility issues: Exterior waterproofing cannot be installed if there are additions, attached garages, or close buildings in the way

All tips above are found in the National Park Service’s Brief 39. For more in depth information on moisture issues throughout your home, as well as steps to take to prevent or manage this, please see: Preservation Brief 39: Control Unwanted Moisture