The Impact of Grading on Foundation Moisture Infiltration: Tennessee Inspection Services Explains

August 10, 2019
by Charlie Priest

When it comes to the structural integrity of a building, there’s no room for ambiguity. Grading around a property is a prime example of this black-and-white principle. In the realm of construction and inspection, grading either falls into the positive, flat, or negative category, leaving no gray areas in between. Tennessee Inspection Services is here to shed light on the critical role grading plays in safeguarding your property against moisture infiltration during heavy rainfall events.

Positive Grading: Sloping Away for Protection

Imagine a scenario where rainwater cascades down during a heavy storm, only to find its path blocked by a property’s foundation. In cases where proper grading is implemented, the soil around the structure is carefully sloped away, resembling a gentle descent that guides rainwater far from the building. This positive grade, often with a 5% slope over the first 10 feet (equivalent to a 6-inch drop), ensures that rainwater flows effortlessly away from the foundation.

The Science Behind Negative Grading

In stark contrast, negative grading takes the opposite route. Picture the soil around a building’s foundation sloping towards the structure or, even worse, remaining completely flat. During heavy rainfall, this misguided grading approach allows rainwater to accumulate and saturate the soil. The result? An environment ripe for moisture infiltration through foundation walls. As soil becomes saturated, it exhibits capillary action, causing water to wick out and affect porous masonry foundation walls. Over time, this can lead to the foundation becoming saturated and releasing moisture in the form of water vapor. The consequences are high humidity levels and, potentially, water seeping into areas below grade.

The Menace of Flat Grading

Flat grading, often categorized as “wrong” in the grading spectrum, is another offender in the battle against moisture infiltration. As rainwater pools around the foundation due to insufficient slope, it creates an environment where the foundation’s porous masonry walls can absorb moisture. This can result in elevated humidity levels below grade, creating a breeding ground for mold and mildew growth. The potential for long-term damage to the foundation and the property’s overall structural stability cannot be underestimated.

Mitigating Risk: The Role of Swales and Drains

While the ideal scenario is to have a well-executed positive grade, reality sometimes presents challenges that make achieving such grading difficult. This is where the expertise of professionals like Tennessee Inspection Services comes into play. When conventional grading isn’t feasible, the installation of a swale or drain can act as effective alternatives for managing rainwater runoff. These features redirect excess water away from the foundation, preventing moisture infiltration and its detrimental consequences.


Foundation Preservation and Moisture Management

Tennessee Inspection Services emphasizes the importance of proper grading as a foundation preservation strategy. The role of grading extends beyond aesthetics; it’s a critical defense against potential moisture-related issues that can compromise the longevity and stability of a property. Moisture infiltration might not manifest immediate repercussions during inspections, but it’s a ticking time bomb that can wreak havoc during heavy rainfall events.


In the world of grading, there’s no gray area – it’s either right or wrong. The choices made in grading can determine a property’s fate when facing heavy rainfall events. Positive grading ensures rainwater is guided away from the structure, while negative and flat grading expose foundations to the risk of moisture infiltration. Tennessee Inspection Services urges property owners to prioritize proper grading, taking the necessary steps to safeguard their investments against the destructive forces of water. Whether it’s implementing a well-executed positive grade or installing swales and drains, proactive measures can make all the difference in preserving the structural integrity of a property for years to come. Don’t let the rain be your property’s downfall – choose the path of proper grading and moisture management.

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