Foundation Design Principles

The main objectives of foundation design are to ensure that the structural loads are transmitted to the subsoil(s) safely, economically and without any unacceptable movement during the construction period and throughout the anticipated life of the building or structure.

Basic Design Procedure

This can be considered as a series of steps or stages

1. Assessment of site conditions in the context of the site and soil investigation report.
2. Calculation of anticipated structural loading(s).
3. Choosing the foundation type taking into consideration.
   1. Soil conditions.
   2. Type of structure.
   3. Structural loading(s).
   4. Economic factors.
   5. Time factors relative to the proposed contract period.
   6. Construction problems.
4. Sizing the chosen foundation in the context of loading(s), ground bearing capacity and any likely future movements of the building or structure.

Foundation Types

Apart from simple domestic foundations most foundation types are constructed in reinforced concrete and may be considered as being shallow or deep. Most shallow types of foundation are constructed within 2000mm of the ground level but in some circumstances it may be necessary to take the whole or part of the foundations down to a depth of 2000mm to 5000mm as in the case of a deep basement where the structural elements of the basement are to carry the superstructure loads. Generally foundations which need to be taken below 5000mm deep are cheaper when designed and constructed as piled foundations and such foundations are classified as deep foundations. Foundations are usually classified by their type such as strips, pads, rafts and piles. It is also possible to combine foundation types such as strip foundations connected by beams to and working in conjunction with pad foundations.