By Bob Brown
It is a pattern that Phoenix homeowners know all too well. Beginning in July, the Arizona monsoon season begins with an increase in thunderstorms and heavy rainfall typically lasting until mid-September.
While the season is short, Ahwatukee residents can easily experience an upward movement of the ground below their foundation as the area’s clay soils swell with increased moisture. Known as “ground heave,” the impact can be long lasting, with cracks in brickwork, floor tiles, or windows as telltale signs.
Although the forecast for this year’s monsoon season calls for a slightly later arrival, the rains are expected to be heavier than usual. And the monsoon can indeed be wet.
The National Weather Service Tucson office and the Climate Prediction Center are predicting that this will be a wetter-than-average year, based on computer simulations.
As a result, it is important for homeowners to understand how to properly address ground heave because what they don’t know can cost them dearly.
It all starts with the unique Ahwatukee soil composition. Given that the soil has more clay than in other parts of the country, coupled with an arid climate, when rains drains off a roof, it has nowhere to go other than under a foundation and floor slab.
Wet soil swells and can lift a foundation in what is referred to as “heave.” Similarly, a foundation can sag after it dries known as “settlement.”
Both heave and settlement can cause serious damage to a home’s foundation. The issue for homeowners is to determine which has occurred, since the resolution for heave and settlement differ significantly.
In fact, even foundation repair service companies can be quick to diagnose settlement as the issue because the industry is oriented to selling settlement products. There are far fewer solutions for heave.
More than 80 percent of the foundation issues in Arizona are misdiagnosed. So a careful, thorough analysis of all data is necessary to compose an engineered repair plan that addresses the problem. Hasty or on-the-spot analysis, often from a salesperson visiting your home, should be avoided.
A common solution for settlement involves stabilizing and raising foundations using a variety of support piles or underpinnings driven into the ground until it contacts load-bearing soil or rock. But if the home is experiencing heave, not only is underpinning a home of no value, but it can actually place more stress on the structure.
There are several ways to remediate heave, some of which can require invasive procedures and are therefore expensive. This includes the use of cutoff walls or removal or replacement of the interior slab.
Grading and drainage improvements are typically recommended but may not provide the complete answer.
A simpler, less expensive approach is to essentially accelerate the process of drying out the soil. The process, called the Moisture Level Smart Foundation System, costs a fraction of traditional underpinning, natural dry air is drawn in from outside the home.
The dry air picks up moisture through evaporation and is vented out of the home through gable vents or another convenient spot using a quiet and energy-efficient fan.
The process can take six months or longer to completely dry out the clay soil and often remains in place to mitigate future moisture accumulation.