Principles of Foundation Design

The main objective of foundation design is 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

These 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 –

a. Soil conditions

b. Type of structure

c. Structural loading (s)

d. Economic factors

e. Time factors relative to the proposed contract period

f. 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 2m 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 2m to 5m 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 5m deep are cheaper when designed and constructed as piled foundations and such foundations are classified as deep foundations. Also, foundations are usually classified by their types such as strips, pads, raft, 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.

Guide to Strip Foundation Width