The soil and hot, arid climate in Tucson are the main culprits responsible for the frequent foundation problems. We’ll explain each of the causes below and the negative impact they have on the concrete beneath your house.
Most homes in Tucson are built on top of expansive soil. The Tucson soil series is defined by its abundance of clay, one soil constituent that is especially problematic for construction.
Generally speaking, there are two significant problems with building on the clay-rich soil found in Southern Arizona.
First, clay particles are very small and maintain tiny gaps that can easily absorb and hold water. Although groundwater is sparse in Arizona, any moisture from precipitation can cause the ground to expand, placing undue pressure on your concrete foundation.
The swelling earth can create enough movement to cause fissures in your slab, often creating severe structural problems that are costly and time-consuming to repair.
A more prominent issue in the arid Arizona climate occurs when the soil dries and becomes less voluminous. The clay soil shrinks and pulls away from your foundation, causing the concrete to settle further into the ground.
Settlement is typical, but differential settling is a widespread problem due to how quickly the clay soil can dry under certain parts of your foundation.
Uneven drying causes erratic ground movement and can lead to instability under your home. Over time, variances in support can crack your foundation and contribute to structural issues.
One of the most appealing aspects of living in Tucson is the abundance of hot, sunny weather throughout most of the year.
Temperatures in the summer regularly reach over 100 degrees, and the humidity is generally low, creating ideal weather for enjoying the outdoors.
Unfortunately, these conditions also contribute to differential settling. High air temperatures and abundant sun contribute to dry soil, as they cause any water that does accumulate in the ground to evaporate rapidly.
When rain falls in Tucson, the soil expands and pushes against your foundation. The extreme temperatures and intense sun cause the earth to lose its moisture content quickly, thereby leaving it to shrink away from your foundation.
The rapid fluctuations of moisture in the soil create excessive ground movement that is hazardous to rigid concrete foundations that are unable to flex with the earth.
Below-Average Rainfall & Drought
Another benefit of homeownership in Tucson is the lack of rainy days. The city experiences just 10 inches of rain annually, which is about one-third of the national average. The infrequent and minimal precipitation contributes to the extreme risk of drought for extended periods throughout the region.
The excessively arid desert conditions in the city lend themselves to differential settling, as they often leave the soil to dry completely and shrink to its minimum volume.
This occurs quickly and often unevenly, which is dangerous, and it also means that expansion will be excessive when the rain eventually does fall and replenishes the soil’s moisture content.
From July through September, Tucson experiences a surge in rainfall as Arizona monsoons rush through the area. These months can bring up to ten times the monthly average rainfall as the dry season.
The passing monsoons, thunderstorms, and frequent precipitation saturate the ground and cause it to expand.
The hydrostatic pressure on your foundation during this time can cause structural problems and fissures to form in your slab, especially as the soil goes from entirely dry to abundantly wet in a short amount of time.
Once the monsoon season is over, the ground quickly reverts to its minimal volume, once again contributing to uneven and hazardous settlement.
Finally, earthquakes in Tucson can promote foundation instability and damages over time. Luckily, the major fault lines along the Pacific coast are far enough from the city that major earth movement is rare. However, small quakes occur on a regular basis in Southern Arizona.
The earthquakes in the region alone are likely not enough to cause significant damage to your foundation. However, when combined with the excessively dry soil and the already high risk of differential settling, they can contribute to instability and structural problems.
Additionally, ground shaking and the resulting foundation movement can damage plumbing lines that run through your slab, causing dangerous underground leaking.