Isolated columns or normally supported by different types of foundations e.g. spread footing, combined footing, pile foundation, etc. The design of the foundation is a challenging task. A foundation engineer must be careful during designing the building foundation.

Foundation thickness should be determined from one-way and two-way shear requirement calculations. However, there are code-specified minimum values for different types of foundations. Following are two code references (ACI and BNBC) for the minimum thickness value of concrete footing.


Depth of footing above bottom reinforcement shall not be less than 150 mm for footings on soil, nor less than 300 mm for footings on piles.

Section 15.7, ACI 318-08
Type of FootingMinimum ThicknessRemark
Masonry 250 mm; twice the maximum projection from the face of the wall Greater of the two values shall be selected
Plain concrete 200 mm, or twice the maximum offset in a stepped footing
Reinforced concrete (depth above bottom reinforcement)
Resting on soil
Resting on pile

N.B. Two storeys or less in Occupancy category A, B, C and D.

Table 6.3.6, BNBC 2006

In conclusion, understanding and implementing the specified minimum thickness values from reputable codes like ACI and BNBC are vital steps in the foundation design process. Engineers must exercise diligence in incorporating these standards to guarantee the stability, durability, and safety of structures.

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Please note that the information in is designed to provide general information on the topics presented. The information provided should not be used as a substitute for professional services.


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