Wet Basements

Wet basements plague many homes. A wet basement can lead to foundation failure and cause air quality mold problems. This brief will be an introduction to discussing various causes and some of the approaches to monitor and remedy water and moisture entry problems. Sometimes homeowners do not realize that they have a basement water entry or moisture problem.  Professional assistance may be needed preferably from people who are not selling specific “waterproofing” products.

If you detect a musty odor there may be moisture entry and potentially a mold problem. The problem may not be visible.  Water, organic material (such as wood or paper), and humidity allow mold production. Environmental and health mold experts are needed to evaluate conditions when there is a problem that will affect you or your family.  This brief will deal with building and site conditions that permit moisture intrusion.

Water adversely affecting buildings has many forms. Rain water, surface water, ground water, condensation water, and plumbing water are the primary suspects.  Water is in the air we breathe. Warmer air will contain more water than colder air. This is why when one breathes on glass moisture condenses out.  The dew point is the temperature when the air will release water from the gas state (vapor) to water in the liquid state. The dew point temperature may exist on a basement steel column or within an exterior wall cavity. The basement steel column will eventually exhibit rusting.  The interior of an exterior wall cavity is not likely visible.  It is complicated to determine when a dew point will be experienced within a wall.  Water can enter a building through openings in the exterior envelope. Wind driven rain will increase the potential for water entry. Sometimes capillary or wicking action will suck water into a building. Water saturated soil against the foundation wall can cause pressure to drive the water through porous masonry. Elevated ground water can cause pressure to drive the water up into a basement through porous concrete or openings in the basement floor. Special conditions such as flooding require flood resistant or elevated construction to prevent problems that is beyond the scope of this discussion.

Rain water generates roof water and surface water. Getting roof water and surface water away from the foundation is the first priority. Each inch of water on a 1,500 square foot building would generate 935 gallons of water. When this water is not diverted away from the foundation, serious problems can result. An easy way to understand where roof water is affecting the foundation is to observe ponding of water when it is raining so hard (2-4 inches per hour) that were you driving you could barely see the car ahead.  During these short periods of extremely heavy rain water overflowing the gutters and ponding of water at the foundation will be evident.

Adverse drainage grading is a significant source of water wetting the foundation walls. Even meeting building code requirements for drainage may not be adequate to assure all surface water flows away and downhill from the foundation walls. Sometimes a drainage slope of one to two inches drop per foot for 12 or more feet is needed.  On relatively flat property swales may be needed or a drainage system that collects the water and pipes it to dry wells. When there is overflowing roof water and relatively flat grading it may be necessary to construct a water collection system on the ground adjacent to the foundation that pipes roof and surface water to dry wells.

Openings in the building envelope (roof and walls) will allow water entry particularly during strong winds.  Sometimes a specific wind direction and velocity creates water entry. Brick veneer that lack drainage weep systems are vulnerable to moisture intrusion from wind driven rain. Even vinyl siding, with drainage openings, is vulnerable to wind driven rain water entry. Exterior insulation and finish systems (EIFS) without drainage provisions or with poor sealant systems are vulnerable to moisture intrusion. Leaking plumbing piping and leaks from water using home appliances are sources for water entry.

Recommend monitoring for moisture or water entry as part of you maintenance check-up at least once a year and after major rain storms.  Consider monitoring instrumentation to detect basement water.