Viewing a basement for the first time—whether cluttered with junk or furnished with a pool table and wet bar—often evokes one very familiar question from home-shoppers looking over a potential property: Does it get wet when it rains? It’s an important question that can highlight a number of trouble spots in a home. This condition is more common than you might think. In fact, it is estimated that six out of ten residential homes in the U.S. have experienced basement moisture issues, with a significant number of these properties dealing with mold and mildew formation brought on by the dampness. This is why this blog makes it a point to revisit this topic every year or so.
It’s important to remember that heavy precipitation—plus the conditions and defects that let this moisture inside—is only one reason a basement may show evidence of wetness. The following are some common conditions that contribute to basement moisture that have been observed by the certified home inspectors at A-Pro after evaluating many thousands of homes over the last 27 years.
A note about basement inspections and water: Your inspector will check walls for dampness and the floor for the presence of standing water (perhaps from a recent rain). Obviously, not all inspections can be performed when there’s a torrential downpour that provides real-time, active evidence that the basement either holds strong against the onslaught or takes on water like a leaky rowboat.
Perhaps the area hasn’t experienced rain in several weeks, leaving walls and the floor dry to the touch. Still, the inspector may be able to cite evidence—both inside and out—that indicates past water problems, in addition to conditions that render the basement vulnerable to moisture penetration. Indicators of water issues include stained surfaces, musty smells, visible mold, rotting wood structures (e.g., trim board), carpet decay, spalling of concrete, efflorescence (crystalline-type salt deposits), repaired cracks, gaps where floors abut poured concrete walls, rusted beams, rusted nails and carpet tacks, stains or rust on the bottom of appliances, decaying drywall at floor level, curled basement floor tiles, pronounced water lines on surfaces (evidence of past flooding), and other signs that may throw up red flags to an experienced home inspector.
Foundational Cracks: The home inspection report will include mention of structural cracks that may be contributing to a wet basement by providing easier access to moisture—a situation that could lead to mold growth, structural damage, and high humidity.
Basement Windows Wells: Window wells clogged with leaves, dirt, and debris can make underground basement windows susceptible to leaks. Runoff from the roof due to a failed gutter system (see below) will find window wells a convenient receptacle to collect in and cause problems. Often, basement windows are made from cheaper materials that can worsen the threat. Your inspector will report on aging basement windows that are showing signs of corrosion and decay.
Gutter System: During the exterior portion of the inspection, gutters and downspouts will be checked to see if they are properly set up to direct rainwater and melting ice and snow away from the foundation (once again, unless it’s raining at the time, it’s impossible to observe the flow of water in action). However, defects will be noted: clogged, sagging, broken, or missing gutters; gutters pulled away from the roof; ice dams in winter; gaps in downspouts that allow leakage; missing downspout sections; or terminations that actually direct water toward the foundation. Other evidence of gutter concerns may include saturated soil at the base of the home (or pooling water) and exterior staining from water cascading off the roof or leaking through a gutter.
Poor Grade: Rainwater is much more likely to find its way into your basement if the soil around the foundation slopes downward toward the home (negative grade) rather than directing it away (positive grade). This will be highlighted in the home inspection report. A concrete or asphalt driveway (or masonry patio) that slopes toward the home’s foundation may also be the culprit if you find water gathering around the base of the house.
Saturated soil from a failed gutter system and negatively graded soil can create water pressure that pushes moisture through porous foundation walls. Further, lateral pressure caused by soil expansion can damage foundations and lead to basement leakage.
Humidity: High indoor humidity is a common cause of a musty, damp basement. Leaky pipes, foundation cracks, and lack of basement insulation can contribute to this harmful condition. Ways for homeowners to reduce this problem include sealing dryer vents, insulating basement pipes, and insulating basement walls.
Plumbing Issues: Burst pipes, slowly leaking pipes, backed-up drains, and blocked fixtures can all lead to water in a basement. Water from a leaky toilet in a bathroom above the basement, for example, may be finding its way into the space below.
Leaky Water Heater: Your inspector will check to see if the water heater is leaking. Such leaks can range from minor and repairable to major issues that will require replacement of the unit. Corrosion of the tank’s inner liner due to sediment buildup, a leaky drain valve, or leaky pressure relief valve are possible causes. Regular maintenance of the tank, such as annual flushing to remove sediment, is recommended to help extend the life of this hard-working appliance.
Sump Pump: Your inspector will check various aspects of this useful device that’s designed to prevent intrusion of groundwater and surface runoff before damage can result. Possible defects include a jammed or tangled float, dirt and debris clogging the pump, and a pump that doesn’t expel water upon testing.