This part of ISO 19901 contains provisions for those aspects of geoscience and foundation engineering that are applicable to a broad range of offshore structures, rather than to a particular structure type. Such aspects are:

Particular requirements for marine soil investigations are detailed in ISO 19901‑8.

Aspects of soil mechanics and foundation engineering that apply equally to offshore and onshore structures are not addressed. The user of this part of ISO 19901 is expected to be familiar with such aspects.

ISO 19901‑4 outlines methods developed primarily for the design of shallow foundations with an embedded length (L) to diameter (D) ratio L/D < 1 (Clause 7) and relatively long and flexible pile foundations with L/D > 10 (Clause 8). This part of ISO 19901 does not apply to intermediate foundations with 1 < L/D < 10. Such intermediate foundations, often known as 'caisson foundations', comprise either shallow foundations with skirts penetrating deeper into the seabed than the width of the foundation, or shorter, more rigid and larger diameter piles than those traditionally used for founding offshore structures. The design of such foundations can require specific analysis methods, and any extrapolation from the design methods described in this part of ISO 19901 to intermediate foundations should be treated with care and assessed by a geotechnical specialist.