There are several factors at play in Denver that contribute to problems under the home. We’ll discuss these in detail below.
The most significant issue for Denver foundations is the expansive soil. The dirt in the area has an unusually high concentration of clay. Clay is present in all soil, but Denver’s higher ratio causes foundation damage for three primary reasons.
Expansive soil expands when it gets wet, sometimes growing up to 10% in volume. As the soil around your foundation expands, it puts added stress on your concrete block walls and slab. The inward pressure of the surrounding soil can eventually cause bowing of your concrete and cracking, both of which can indicate a loss of structural stability.
Clay-rich soil loses significant volume as it dries, creating additional foundation issues if it shrinks away from your concrete. Your foundation relies on the ground around it for stability, so areas of concrete that lose that support due to shrinking soil can quickly become unstable.
Unsupported concrete typically cracks off the rest of your home and settles into the ground. This is a severe problem if the soil sinks at various rates, a dangerous phenomenon called differential settling.
Lastly, clay retains water longer than typical soil, which means it can hold moisture from runoff against your concrete for extended periods. The longer water is in contact with your foundation, the more likely it is to seep in through cracks or pores in the concrete. As such, water intrusion is a widespread problem in Denver homes.
Bentonite in the Soil
In addition to the standard clay found in expansive soil, Denver and the surrounding area has a somewhat unique constituent to its dirt: bentonite. Bentonite is a clay that forms from the degradation of volcanic ash as it mixes with salt or seawater. It can hold up to five times its weight in water and expand to fifteen times its original volume in the presence of moisture.
Bentonite is a severe issue in Colorado for many of the same reasons why the expansive clay soil is a problem. However, it causes more excessive ground movement and can very rapidly cause structural damage to your home’s foundation.
Colorado is commonly ranked as one of the driest states in America, experiencing an average of around 15 inches of rain annually. This is less than 50% of the national average, and while it’s great for enjoying the outdoors, the dry climate can cause significant foundation problems.
Days or weeks without rain give the soil ample time to lose moisture. All dirt provides less stability to a foundation when completely dry, but Denver’s expansive soil can shrink excessively in dry conditions. It can pull away from the concrete, leaving your home without the support it needs. Dry periods can contribute to differential settling, foundation sinking, and a loss of structural integrity.
Heavy Snowfall & Mild Winters
The melting of the snow in any area creates runoff, which soaks into the soil. The more snow an area receives, the worse the problem with soil movement will be, and the more pressure is placed on concrete foundations that can’t bow and flex with the soil.
Although Denver gets significantly less rainfall than much of the United States, it does experience above-average snowfall. Residents can expect an average of 50 inches throughout the year. The significant runoff created by the snow melting can place excessive stress on your foundation.
To make the issue worse, Denver experiences relatively mild winters, with temperatures averaging in the 40s. As a result, the snowfall that the city does get typically melts in just a few days. The heavy snowfall all melting in a short period means a lot of runoff that will come in contact with the ground around your foundation.
The expansive soil in Denver compounds the problem with melting snow. The runoff meets with the clay and bentonite in the dirt, causing the ground to swell more than it would in areas with typical soil.
Additionally, the otherwise dry climate in the area makes the snowfall more hazardous to home foundations. When expansive soil goes from dry to wet and back again in a short amount of time, the soil swells and shrinks rapidly, creating constant movement around your home.