Read on to find out what is foundation settlement? What sorts and sources of it might cause harm to your building
Foundation is an integral part of a home that supports the stability of the entire structure. Therefore it must be constructed efficiently and correctly. While we focus on high-quality material and the process of construction, the soil supporting the foundation is often overlooked. Here is how the shifting of soil impacts the foundation.
What is Foundation Settlement?
- Over time, the soil deforms under a load of foundation structure. This may give rise to displacement and shifting of the soil below a home. This phenomenon is known as foundation settlement.
The magnitude of foundation settlement depends on foundation structure and the type of soil. For instance, bedrock foundations rarely settle, while foundations built on clay soil settle to a greater degree.
Causes Of Foundation Settlement
Keep reading to find out some of the potential causes of foundation settlement.
Changes In The Moisture Content
- When the soil beneath the foundation changes the moisture content, it can cause damage to the foundation in the form of soil shifting or settlement. When there is excess moisture in the soil, the soil becomes saturated.
It causes softening of the silt or clay soil. This softened soil can no longer support the load and results in soil settlement.
What Causes Soil Saturation?
The soil beneath the foundation becomes increasingly saturated with moisture due to:
- Poor drainage around the structure
- Leaks in the sewer lines
- Leaks in the plumbing
- Elevated groundwater table
Shrinkage Of Foundation Soil
- Soils with higher clay content have a greater tendency to absorb moisture. When the enriched clay soil dries out, it contracts and shrinks. As a result, a gradual decrease in soil volume occurs.
When this happens, the foundation begins to settle, thereby leading to structural damage. Maturing vegetation and trees can also absorb moisture from the soil and cause drying out of the foundation soil.
Poor Compaction Of The Soil
- When developing commercial subdivisions and residential subdivisions, buildable lots are created by making spaces that are flat and compact. This is often done by cutting down hilltops or by filling in valleys. Fill soils can efficiently create an adequate amount of support for the foundation, given that they are placed and compacted correctly.
However, if these fill soils are not compacted sufficiently, they may give in under the load of the foundation and compress. The compressing of the soil will result in the settlement of the foundation. This compromises the integrity of the whole building.
Weak Bearing Soil Issues
- When it comes to supporting the weight of the foundation, certain types of soils are incapable of doing the job. These soils simply cannot bear the pressure exerted by the foundation of the building. The foundation built on weak soils can press down or sink into softer soils. The best way to lay a strong foundation is to design the footing in such a way that it distributes the load across the weaker soil. This can go a long way in reduction of the potential settlement.
Use Of Incorrect Footing
- Most problems arise when the standard footings are used in residential construction instead of the better load-bearing footings. During construction, the footings are usually designed based on the general guidelines rather than the soil information of the local area. The foundation laid on weaker soil will eventually settle and cause structural issues.
- The settlement that occurs at the same rate throughout all building parts is referred to as uniform settlement. The whole structure sinks vertically, which causes the integrity of the building to remain unaffected in most cases. Likewise, the foundation sinks uniformly when all building parts rest on the same soil.
Also, when the design of the structural system is uniform, the settlement would be uniform. Usually, the uniform settlement has a negligible effect on the safety of the building. However, connected piping, sewer lines, water supply, cables, and other utilities of the building will be damaged due to uniform settlement.
Differential Foundation Settlement
- Differential settlement corresponds to a different rate of sinking for different building parts. Differences in the soils, loads and structural systems can cause unequal vertical sinking of the foundation. This results in the settlement or sinking of different parts of the building at varying rates.
The structure of the building tilts in the direction of the tilting foundation, which causes additional shear, bending, stress, and torsion in structural parts of the building. As a result, cracks may appear in the foundation, structure, or finish, floors may slope, and doors and windows may not open properly. This type of foundation settlement leads to the majority of foundation failures.
- In addition to uniform and differential settlement, sometimes the structure may tilt to one side leading to tipping settlement. Subsequent settlement causes tilting of the foundation. In tipping settlement, the foundation on one side remains unaffected, and the second and third grid settles.
But the third grid will settle more than the second and so on. Tipping settlement usually does not damage the structure of the building. However, as time passes the structure may overturn.
Methods To Correct Foundation Settlement
The correction methods depend on structure, soil type, reason of settlement, and the cost of application.
Correction Of External factors
It is important to thoroughly inspect the site and check the following points:
- Presence of nearby trees and bushes
- Leaks in the sewer lines, HVAC lines, water lines, etc.
- Rat holes, termite or ant burrows near the foundation.
- Underpinning is another important method that is used for preventing further settlement of the foundation. In this method, the major load is transferred to the deeper strata in an attempt to strengthen the foundation. It is often done in combination with shoring.
- In grouting, a liquid is injected into the foundation soil. Grout is usually made of a mixture of sand, cement, and chemicals. This mixture is used to fill gaps, and repair cracks in the concrete, for sealing and waterproofing purposes.
This helps protect the soil from erosion. In addition, grouting helps reduce water seepage and improves load-carrying capacity. The different types of grouting include:
- Chemical grouting
- Jet grouting
- Cement grouting
- Bituminous grouting
Advantages Of Grouting
- Grouting can be performed easily in most ground conditions.
- It does not involve vibrations that endanger structural integrity.
- Grouting is especially advantageous for limited space and low headroom applications.
- It can lift or level a deformed foundation.
- Grouting helps control water seepage, groundwater flow, etc.
Are you also dealing with foundational issues? Give us a call at 877-727-2259. Addressing the foundational issues quickly and effectively is the best way to preserve the integrity of your structure. Our experts from Crack-X will assess the damage and provide necessary foundation repairs. Crack-X is a structural repair company located in Maine and New Hampshire.