How Moisture Exposure Damages Foundations

Key Takeaways:

In this article, you’ll learn how:

• Foundation moisture problems can affect structures internally and externally
• Inadequate ground slopes may result in water intrusion to crawlspaces
• Hydrostatic pressure could lead to above-ground structural losses

Many homeowners contend with residential water intrusion, and if it’s not addressed early, it can lead to mold growth, deterioration of organic construction materials, foundation gapping and cracking, wall failures, or uneven roof lines.

Insurance professionals should be aware of three of the primary causes of water-related foundation damage: poor drainage, inadequate ground slope, and hydrostatic pressure.

Inadequate Drainage

The external features of a home should be designed to direct water away from the structure. Downspouts are a key part of this system, carrying water from the roof and channeling it safely onto ground at least 5 feet from the foundation. However, downspouts are often mistakenly directed to discharge much closer.

Over time, water can infiltrate or erode the soil around the foundation and seep through the concrete and into the basement or crawlspace. Excess soil moisture contributes to foundation settlement, causing the house to sink. This moisture also leads to continuously damp wood that will begin to rot and degrade, which can cause the affected section of the house to shift.

This section of downspout discharges directly into the soil adjacent to the foundation, and it has caused foundation damage.

Inadequate drainage can also lead to mold, which requires the following five conditions to flourish:

1. A surface to grow on
2. Air
3. Moisture
4. An appropriate temperature, which varies among species of molds
5. Dead organic matter to consume as a food source

Drywall and wood are common food sources for mold, which makes it particularly damaging to home interiors. Basements and crawlspaces frequently provide additional favorable conditions for fungal growth due to their low light and low air movement.

The mold growth in this basement was caused by inadequate drainage.

Ground Slopes

Ground slopes, or the grade around the home, is also a significant factor in foundation-related moisture problems. The International Residential Code requires a minimum of a 6-inch vertical drop for every 10 feet of ground away from a building’s foundation. This equates to a 5% slope away from the structure.

If the ground slopes toward the home, surface water drains into the soil around the foundation. This can damage foundation walls or supporting footings.

As foundation elements shift, water may enter a crawlspace or intrude through gaps that develop between a basement wall and concrete slab. Building elements that are unable to support the house due to reduced capacity could lead to interior and exterior cracking.

The surrounding ground slopes toward the home’s foundation at a rate of 7.7 percent, which is more than a 6-inch vertical drop toward the structure for every 10 feet of ground.

Hydrostatic Pressure

Hydrostatic pressure is the weight of resting water against a foundation or basement wall when the soil is saturated, either by poor drainage or flooding. Gravity forces water into the soil, which causes it to push against the structure. This pressure increases with depth and can be lateral or vertical, meaning it could twist structural elements, or push them up or down.

Hydrostatic pressure can force moisture through pores in the basement wall and can crack and/or buckle walls. This damage can lead to serious structural losses above ground, including:

• Interior and exterior cracking in walls and wall coverings above weak points in the foundation
• Sections of the structure rotating in the direction of the pressure
• Uneven roof lines

This diagram illustrates the path water takes into a home when drainage is poor and hydrostatic pressure builds belowground.

Insurance professionals should understand the source and duration of water exposure to foundations in order to make an informed decision about related losses. Donan Engineering, part of the Alpine Intel suite of services, is equipped to answer complex and challenging questions about property damage, including foundation-related losses. Our licensed engineers deliver actionable intelligence and conclusive findings through peer-reviewed reports. Submit an assignment today.

Engineering services are provided by or subcontracted to Alpine Intel Commercial Solutions, LLC, Alpine Intel Commercial Solutions, PLLC, Donan Engineering, LLC, Donan Engineering NC, PLLC, Donan Forensic, LP, BSC Forensic Services, LLC, or BSC Experts, PLLC.