A ship must not only be efficiently designed, it must also be soundly built, and the certificate of an independent body as to quality of design and construction may help a shipowner to convince an insurance underwriter that his ship is seaworthy. Such independent bodies are known as ‘classification societies’. There are numerous societies but the oldest, one of the largest and perhaps most famous, is Lloyd’s Register (LR). There is an International Association of Classification Societies (IACS), founded in 1968, and IACS members classify around 90% of the world’s gross tonnage. IACS consists of 10 member societies and 1associate. In 2005 IACS agreed common shipbuilding rules which came into force in 2006. There are about 40 small classification societies which are not all IACS members.
Classification is voluntary but few shipowners would or could operate without it. It is not only the underwriters that the shipowners have to convince of a ship’s seaworthiness but also the charterers, shippers, financiers, various cargo interests and the port state authorities of the countries the ship will visit.
Lloyd’s Register includes all ships over 100 tons gross, whether classed with Lloyd’s or not, and that's why LR is often referred to as the ‘shipping man’s bible’.