How monsoons damage your foundation — and what you can do

10:43 AM, Jul 23, 2020
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In a state known for heat and dryness, monsoon season may seem like an anomaly — but it hits Arizona every year from June to September, according to the National Weather Service, and the area can become a flood zone in minutes.

In fact, much of northern Arizona gets about half its annual rainfall during monsoon season.

“Rainfall during these months is not continuous but comes most days in the form of afternoon and evening thunderstorms,” the NWS says. “It is incorrect to call one single thunderstorm a ‘monsoon.’ Instead it is a large-scale weather pattern that causes these thunderstorms.”

The amount of rainfall varies from year to year, with the last 12 years seeing anywhere from 3 to 15 inches in the Flagstaff region. The total depends on changing weather patterns, but any heavy precipitation can wreak havoc on your home.

That’s why it’s important to be prepared. Here are three facts you need to know about how monsoon season can affect your home’s foundation — and what you can do about it.

Local soil expands when wet

The clay-rich soil found in much of Arizona is largely to blame for the damage to homes following monsoon rain. Clay-rich soil is known as expansive soil because it expands as it soaks up water, exerting extra pressure on whatever surrounds it.

“Lab tests have demonstrated that expanding clay soil can exert an uplift pressure of over 5000 pounds per square foot,” Arizona Foundation Solutions says. “That’s more than enough pressure to lift a concrete slab foundation.”

About 80% of the homes Arizona Foundation Solutions visits have some amount of heave from expansive soils.

When the soil dries, it shrinks and leaves mud cracks that show how much the soil has shrunk. You can determine whether you have expansive soil on your property by watching for the following, according to the Arizona Geological Survey:

· Desiccation cracks (mud cracks)
· Popcorn soil texture
· Soil that is sticky when wet
· Cracked foundations and warped roads

Soil upheaval damages foundations

Problems associated with soil upheaval include foundation cracks, slab wall cracking, jammed windows and doors, broken pipelines, and heaving sidewalks and roads, according to the Arizona Geological Survey. These problems may start small but can progress over time.

Ideally, a builder prepared the ground prior to constructing your home to lower your chances of soil upheaval damage, but even the best contractors are at the mercy of expansive soils.

Preventing damage requires maintenance

The key to stopping damage is to keep the soil below your home as dry as possible. Start by maintaining your gutters, checking frequently for leaks or blockages, and adding extended drains to move rainwater far from your home.

Another proactive approach is to install a moisture management system that can regulate moisture below your home. For example, the MoistureLevel Smart Foundation System lessens expansive soil problems

below concrete slab foundations. This repair technique uses a fan and plastic pipe to create air movement and suction on the under-slab soil.

“Introducing outside air to the damp soil causes evaporation to take place, making it possible to reduce soil moisture content and (as a result) damaging soil expansion,” Arizona Foundation Solutions says.

Arizona Foundation Solutions can inspect your foundation for damage and suggest repairs that will keep it strong for years to come. Visit for more information, and call to schedule your free foundation inspection.

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