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The Causes of Foundation Problems and
Basement Wall Cracks

What Causes Foundation Settlement?

Foundation settlement is usually not due to the design of the foundation. Often, the damage to the foundation is a result of changes in the ground that surrounds the foundation. Following are brief explanations for a few of the more common causes of foundation settlement.

Weak Bearing Soils

Some soils are incapable of supporting the weight or bearing pressure exerted by a building's foundation. The footings of the house may press or sink into the soft soils. In these instances, footings may be designed to spread the load over the weak soils, thereby reducing potential foundation settlement. The majority of settlement problems caused by weak bearing soils occur in residential construction, where footings have been designed based upon general guidelines and not site-specific soil information.

Poor Soil Compaction

Placement of fill soils is a common practice in the development of both commercial and residential properties. Generally, raised land is flattened and gullies filled to create buildable lots. Properly placed and compacted fill soils can provide adequate support for foundations. Improperly spread soil can compress under a foundation load resulting in settlement of the structure.  

Changes in Soil Moisture Content

Extreme moisture changes within soil can result in damaging settlement. Excess moisture saturates the ground and leads to softening clays and silts. A reduced ability of soil to support a houses load can result in foundation settlement. Increased moisture within foundation soils is often a consequence of poor surface drainage, leaks in water lines or plumbing, or a raised groundwater table.

Clay-based soils have a tendency to contract with moisture loss, resulting in a decrease in soil volume. Therefore, settlement damage can also be observed in a structure supported on dried-out soil. Drying of foundation soils is commonly caused by drought, maturing trees and vegetation, and leaking subfloor heating, ventilation, and air conditioning (HVAC) systems. 

Maturing Trees and Vegetation

Maturing trees, bushes and other vegetation in close proximity to a home or building are a common cause of settlement. As trees and other vegetation grow, so does their need for water. Root systems expand and draw moisture from the soil beneath the foundation. Many home and building owners often state that they did not have a settlement problem until decades after the structure was built. This time frame coincides with the maturation and of the vegetation that surrounds their home.

Foundations closer to the surface are more often affected by soil dehydration due to tree roots than are deep, basement level foundations. As a general rule, the diameter of a tree's root system is at least as large as the tree's canopy.

Soil Consolidation

Consolidation occurs when the weight of a structure or newly-placed fill soils compress lower, weak clay heavy soils. The applied load forces water out of the clay soils and compresses it. Consolidation results in downward movement or settlement of overlying structures. Settlement caused by consolidation of foundation soils may take weeks, months, or years to be considered "complete."

Roadways and Street Creep

Surprisingly, nearby roadways can cause significant damage to foundations. Roads expand when heated and shrink when they cool. As they expand, and especially when a home is located at the end of a T-intersection or cul de sac, the expanding street will push against the driveway. This causes the driveway to push against the concrete garage slab, and consequently against the foundation walls. This process will cause wall deflection and cracking. Gaps that are created to help avoid this situation problem may work for a period of time but will generally fill with debris and gravel over the years and become ineffective. Because obstructions settle within the bottom of the gap, it may be obstructed even when it appears open and clear from the top.

Vibrations from passing traffic can also do damage to foundation walls. When a home is located along a major roadway, and particularly when that roadway accommodates large trucks, the continued vibration of the earth can weaken foundation walls and damage a home over time.

Service Area

Foundation Repair of Western Colorado, LLC services North and South Western Colorado. See our service area page for more information.

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