Being able to complete a foundation design is a highly specialized function and usually is performed by a structural engineer. It requires study and examination of multiple components, and it is the main structure of any building, since it is the base of it.
The required depth of the foundation will depend on several factors like:
1. Soil bearing capacity. How much load the existing soil can withstand.
2. Type of soil. This depth will vary depending on the type of soil beneath the structure.
3. Depth of frost penetration in case of fine sand and silt.
4. Height of ground water table. This will usually be reported on the soil study.
5. The minimum depth should not be less than 18 inches to allow removal of top soil and variations in ground level. However, depending on the structure, the engineer will select the best depth.
The foundation is usually built in brick work, masonry or concrete under the base of a wall or column. This will enable to transfer the load to the soil in a uniform manner and allow the transition from the structure to the soil. It will depend on the recommendation by the structural engineer. He will select the location, width and depth of every foundation in the structure. For smaller and lightweight structures, the design will be different depending on the material and location of the structure.
Usually dry and uniform graded dense materials should have maximum shear resistance and maximum bearing capacity. In general submerged soil and clay have fewer bearing capacities, reducing the capacity to handle loads imposed by the structure.
Foundation Design Precaution
The foundation will be designed in a way that loads will be transferred uniformly to the contact surface.
It should be designed to transmit the sum of dead load, live load and wind load to the ground. The net loading capacity coming into the soil should not exceed the bearing capacity of the soil. Settlements expected from the building will be design in such way that they will be controlled and uniform for the complete structure to avoid damages to the structure. Whole design of the foundation, super structure and characteristics of the ground should be studied to obtain benefits during construction work.
Recommended Foundation to Avoid Cracks
There are several types of foundation use in the construction industry. The most ‘secure’ one is the mat foundation. A mat foundation is a uniform slab acting as the footing for the building. It is thought as the most secure, because there is no gap to allow for differential settlements and will act as a mat for the whole building. Sometimes due to economic reasons, types of buildings and space limitations is not used and then substituted by other types of foundations.