3.1.2 Loadlines & Plimsoll Mark


The amount of a ship's deadweight is determined by its loadline and this varies slightly because a ship has a maximum depth (draft) to which it is permitted to be loaded. This differs according to the part of the world in which the ship is loading and what season of the year. When reference is being made to a ship's deadweight without any qualification it invariably refers to the amount that can be loaded on 'summer marks'.


The ship's maximum draft and its variations are determined according to an internationally established formula. This international convention was the first one dealing with ship safety and started life in 1876.


Plimsoll Mark

It was then that Samuel Plimsoll a campaigning British politician succeeded in persuading the government of the day to pass a Merchant Shipping Act. This gave the authorities several powers to detain unsafe ships and by an amendment drawn up in 1894 it particularly introduced a loadline. This was the deepest draft to which a ship could be loaded and was shown on the starboard side of the ship by a painted circular disc 12 inches in diameter with a line 18 inches long drawn horizontally through its centre to show the loadline. Because of Plimsoll's involvement, the loadline is sometimes referred to as a Plimsoll Mark.

Location of loadline

The decision as to where the load line shall be situated is made at the time the ship is constructed and the decision process is overseen by the ship's Classification Society which issues the Load Line


Certificate and supervises the placing of the loadline. This mark is situated approximately amidships on both sides of the vessel.


Plimsoll line


The Classification Society's initials (e.g. LR Lloyd's Register of Shipping, GL Germanischer Lloyd (German Classification Society) etc) are included in the loadline. The maximum draft allowed is calculated according to a formula laid down in the loadline convention, but an owner can opt for a lesser draft and, if he does so, a lower NT Net Tonnage can be assigned to the ship. An owner who intends to use his ship for carrying lightweight cargoes might choose this option because it means that port charges calculated on the ship's GT Gross Tonnage, Greenwich Time or NT will be lower.


Loadline and safety

Although, commercially, one associates the load line with the draft of the ship, the depth of the ship in the water, the safety aspect of the load line is concerned with the ship's freeboard, the amount of the ship's hull between the water level and the loadline deck. The level of the deck is indicated by a horizontal line painted on the ship's side above the loadline itself.



Presentation home