What Is Footing In Construction- A Detailed Guide

Footing In Construction

No matter how well-built a structure is, it cannot survive without a stable foundation. That is why footings and their various types are essential to the construction process. Footer construction is a major component of the effective, long-lasting foundations that all construction relies on. Footings are generally the first support built on-site, thus having a thorough grasp of them is essential.

Footings are structural supports that provide additional solidity to a structure’s base. Footings, which are situated beneath foundational walls or columns, are often built of reinforced concrete and help disperse a structure’s weight from the foundation into the earth and soil beneath. Essentially, footings offer another load-bearing point between the structure and the ground. This is especially helpful when developing shallower foundations. As a result, they help transfer weight into the earth so that the structure doesn’t carry as much weight.

Difference Between Footings And Foundations

Despite their similarities, the footings and foundations are not identical. The fundamental distinction between the two is how vital they are to a structure’s stability. All significant structures are built on top of foundations any residential or commercial construction, however, not all of those foundations are supported with footings. However, most building standards require footers for the bulk of projects to maintain foundation stability. In addition to providing stability, footers prevent differential settlement, settlement happens when the earth beneath a structure’s foundation shifts, causing the structure to sink, tilt, or break. Water damage, soil disruption, inadequate weight distribution, and other causes can also cause differential settling.

Slight shifts are to be expected in every construction, but significant ones caused by differential settlement can crack the foundation and cause the structure to collapse. Footings increase weight distribution by minimizing the load on the foundation, preventing significant settlement.

Footing

Factors to Consider in Footing Construction

The International Building Code (IBC) and the National Building Code of Canada provide requirements for footer construction. However, structural engineers frequently provide additional guidance to builders throughout any form of footer building. They are especially useful when developing foundation footers for unusual constructions and project site conditions. In addition to these recommendations, below are some general considerations for building.

Frost Line

The frost line is the lowest point at which water in the soil freezes. Footings must be erected below the frost line to avoid frost heave, which can cause your structure to shift upwards. This happens because when water freezes into ice, it expands. If ice accumulates in the earth beneath your footings, the soil expands and exerts upward pressure on your foundation. Once that occurs, structural integrity is no longer guaranteed!

Water in the soil below the frost line does not freeze, hence frost heaving will not damage footers built at any depth less than the border. Check the frost line in your area, as it differs by geographical region. The needed distance below the frost line, job site circumstances, and load all influence footing depth.

Soil Bearing Capacity

Soil bearing capacity is the maximum pressure that each type of soil can support, which is often measured in pounds per square foot. This criterion is the most important aspect influencing footer design and width requirements. Footings are not necessarily necessary in places with high-carrying capacity soils, as the foundation will sustain the structure on its own. Silt-like soils have a lesser bearing capacity, but gravelly soils may withstand higher pressure. Before construction, soil-bearing capacity can be assessed using equipment such as soil density tests and penetrometers.

Groundwater Table

The groundwater table, or water table, is the depth at which subsurface soil becomes saturated with water. The groundwater table serves as a boundary between dry and moist earth. Unsaturated soil is found above the water table, while saturated soil with water pockets is found beneath it. Water and concrete do not mix nicely. Concrete footings absorb excess water from the surrounding soil, resulting in fractures, an upward displacement of the structure resting on top of the footing, and a reduction in load-bearing capability.

In general, footing building should occur above the water table. However, in locations with a high water table, this is difficult to perform. Helical steel piles are corkscrew-shaped footers that screw into the ground. They operate well in places with high water tables.

Types of Footings

The type of foundation used to support a structure influences which footing you select. Shallow foundations are developed at shallower depths where the soil can support the structure’s load. The following footing types are commonly used to support shallow foundations of any commercial or residential construction. Isolated footings come in three types:

Simple isolated:

Rectangular and square-based supports form an upside-down “T” shape.
Trapezoidal isolation: Trapezoidal supports that require less concrete.

Stepped isolation:

Stepped-based supports, which are less used today, Smaller concrete slabs are layered on top of bigger slabs to make a staircase shape.

Combined Footing

This occurs when two or more columns rely on a common footer. They can handle a “combined” load, hence the name. When columns are close together and there is insufficient space to insert two independent footers, a combined footing is used instead. Typically, this design sustains loads in soils with reduced bearing capacity since its bases are larger than isolated footers and may transfer more weight into the ground. There are three varieties of mixed footing:

  • rectangle combined: This design features a rectangle basis. They support columns of equal weight.
  • Trapezoidal combined: This design features a trapezoidal basis. They support columns with uneven weights. The column that bears the most weight rests on the trapezoid’s wider base.
  • Strap beam combined: Strap footings feature two square bases, one column each, joined by a concrete strap beam. They are utilized on property boundaries if one column at the property’s boundary bears a much larger load than the inner column. Instead of spreading the load’s weight to the ground, the strap beam shifts some of it from the heavier column to the lighter one.

Conclusion:

In conclusion, footings are essential to ensure the stability and lifespan of any construction project. They support the foundation by equally dispersing the structure’s weight into the soil, minimizing settlement and differential settling. To avoid potential damage and maintain maximum performance, footing construction must take into account factors such as the frost line, soil-bearing capacity, and groundwater table. Different types of footings, such as isolated and integrated footings, adapt to different structural requirements and site conditions, allowing for greater flexibility and reliability in building designs. By recognizing the importance of footings and adhering to construction standards and suggestions, builders may lay strong and resilient foundations for long-lasting structures.

FAQs

A footing is like a strong support for a building's base. It's usually made of strong concrete and sits under the walls or columns of a building.

Footings help spread the weight of a building evenly into the ground below. They make sure the building stays steady and doesn't sink or tilt.

Footings give extra support to the foundation. Foundations hold up the entire building.

Builders use different types of footings, like ones that stand alone or ones that support multiple parts of the building.