There are various types of isolated footings such as spread footing, stepped footing, sloped footing etc. They are usually square, rectangular or circular in shape. Each type of footing is selected based on the soil condition and configuration of imposed loads. Isolated footings are one of the most economical types of footings and are used when columns are spaced at relatively long distances.
Isolated or single footings are structural elements used to transmit and distribute loads of single columns to the soil without exceeding its bearing capacity, in addition to preventing excessive settlement and providing adequate safety against sliding and overturning. Furthermore, they are used in the case of light column loads, when columns are not closely spaced, and in the case of good homogeneous soil.
Types of Isolated Footings
1. Flat, Pad, Plain, or Reinforced Isolated Footing
It is constructed under each column independently and is usually square, rectangular, or circular in shape. The thickness of flat isolated footing is uniform. It is provided so as to reduce the bending moments and shearing forces at their critical sections. It can be constructed from plain concrete or reinforced concrete to increase the ultimate load carrying capacity.
2. Sloped Isolated Footing
Sloped or trapezoidal footings are designed and executed with utmost attention to maintain a top slope of 45 degrees from all sides. The amount of reinforcement and concrete used in the sloped footing construction is less than that of plain isolated footing. Therefore, it decreases the utilization of concrete and reinforcement.
3. Stepped isolated Footing
Previously, the construction of this type of isolated footing was popular, but its application has declined nowadays. It is generally used in the construction of residential buildings. Stepped footings are stacked upon one another as steps. By and large, three concrete cross-sections are stacked upon each other to create steps.