Class

Classification societies

Published 28 August 2026 · updated 22 September 2026

A classification society is not a regulator, and a ship being in class is not a statement that she is safe, well run or worth fixing. Class is a private technical standard for the hull, machinery and essential systems, plus a cycle of surveys that says she still meets it. Almost every misunderstanding about class comes from expecting it to answer a question it was never written to answer.

What class actually is

A society publishes rules for design, construction and life cycle maintenance. A ship built to those rules and surveyed against them holds a certificate of class. The society does not own the ship, insure her, operate her or police her. It maintains a standard and records whether this hull still complies.

The compliance is kept alive by a survey cycle rather than by a one-off inspection:

• Annual surveys, a general examination each year within a window around the anniversary date.
• Intermediate survey, more searching, around the middle of the cycle.
• Special survey, the full examination every five years, with thickness measurement of the steel and opening up of machinery. This is the expensive one.
• Bottom and docking surveys, requiring the hull to be examined out of the water or in an approved in-water survey.

Findings that do not stop the ship trading are recorded as conditions of class or recommendations, with a date by which they must be cleared. Class can be suspended when a condition is overrun, when a survey falls due and is not held, or after damage that has not been repaired to the society’s satisfaction.

The second hat: acting for the flag state

This is the part most often conflated with the first. A flag state may authorise a society to issue statutory certificates on its behalf: load line, SOLAS safety certificates, MARPOL certificates, tonnage. In that role the society is a recognised organisation, carrying out a state’s duty under an international convention, not enforcing its own rules.

Two different jobs, two different sources of authority, frequently the same surveyor on the same visit. Class rules are contractual and belong to the society. Statutory certificates belong to the flag and are only administered by the society. The IMO codified this in the Code for Recognized Organizations, adopted in 2013, which sets the standard for how a flag assesses, authorises and oversees the societies it uses. The European Union runs its own recognition regime alongside it.

IACS, and why the societies are not all different

The International Association of Classification Societies publishes Unified Requirements, which member societies must incorporate into their own rules. That is the floor. IACS states that its members between them class more than 90 per cent of the world’s cargo carrying tonnage in international trade.

The practical effect is that the difference between two IACS members is service, network and reputation rather than structural standard. The difference between an IACS member and a society outside it is a genuinely different question, and it is one that charterers, insurers and financiers ask on their own terms. Many charterparties simply require an IACS member society, which turns the question into a term of the fixture.

Class is not port state control

Class is a private relationship the owner pays for. Port state control is a coastal state boarding the ship in its own port, under its own authority, whether anyone wants it or not. A ship can be perfectly in class and still be detained, because the inspector is looking at operational condition, crew competence and how the safety management system is actually working rather than at whether the steel meets a design rule.

The two records complement each other and neither substitutes for the other. If you only get one, take the inspection history: it is the record of how the ship was found, not of how she was approved.

The signals that matter commercially

The society, named. Whether it is an IACS member is a filter that takes one second and is often written into the charterparty.

Notations. Class notations sit on the particulars sheet and are chartering facts, not decoration. Ice class decides whether a Baltic winter cargo is possible. Strengthened for heavy cargoes, and holds may be empty, decide whether ore can be loaded in alternate holds. Grain fitted decides whether she can be offered for grain at all.

A change of society. Moving class mid life is not by itself misconduct, and there are ordinary reasons for it. It is still a question worth asking, because one route past an outstanding condition of class is to find a society that does not have it on file.

The survey date. This is the one that reaches a broker directly. A special survey means a drydocking, and a drydocking takes the ship out of service for weeks at a date nobody negotiates. A position that reads open and clean but has a special survey falling inside the laycan is not a position. It is a ship who is already committed to a shipyard, and the constraint is invisible in almost every position list in circulation.

References

• IACS, Unified Requirements. iacs.org.uk
• IACS, Classification Societies: What, Why and How? iacs.org.uk
• IMO, Code for Recognized Organizations (RO Code), resolution MSC.349(92), 2013. imo.org
• European Union, Regulation (EC) No 391/2009 on common rules and standards for ship inspection and survey organisations, 2009. eur-lex.europa.eu
• IMO, International Convention for the Safety of Life at Sea (SOLAS), 1974. imo.org

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