Chapter 18 ties the foundation to what's under it. A geotechnical report — required in many situations — establishes the allowable soil bearing pressure and the foundation recommendations, and the design has to match them. The chapter covers footings and foundation walls, and where soils are weak or loads are high, deep foundations such as piles or drilled piers.
The core principle is fit: spread footings where bearing soil is adequate, deep foundations where it isn't. The foundation type has to suit the actual site conditions.
A common mistake is a foundation type that doesn't match the geotech recommendations — or a slab-on-grade shown where conditions call for something else, a classic misclassification. Reviewers check that the foundation design references the soils report and that bearing values and foundation type are consistent with it.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.