What Is a Bay Plan and How Do You Read It?

The bay gives the container's position along the length of the ship, normally numbered from forward to aft. The row gives its position across the ship, and the tier gives its height in the stack.

Read together, the three values identify a unique slot on board, so the terminal, the ship and the line all refer to exactly the same place when discussing a container.

The bay plan is a working document constantly updated between the terminal planner and the ship's cargo officer. The preliminary plan prepared before loading is refined by changes made during the operation and shared with the parties before the vessel sails.

In common practice, odd-numbered bays (01, 03, 05) denote 20ft slots. A 40ft container occupies two 20ft slots and is shown by the even number between them, so a 40ft box spanning bays 01 and 03 appears in bay 02.

An even bay number on the plan therefore tells you that a 40ft (or longer) container sits in that position. How 20ft and 40ft boxes can be mixed within a bay depends on the ship's design and its stowage rules.

Rows are numbered outwards from the centreline. Looking aft, rows to starboard take odd numbers (01, 03, 05) and rows to port take even numbers (02, 04, 06). On ships with an odd number of rows, the centreline row is 00.

Tiers rise in even numbers from the bottom up. Tiers in the hold usually start at 02 (02, 04, 06), while deck tiers usually start at 80 or 82. The last two digits of the code therefore show immediately whether a container is in the hold or on deck.

A stowage plan is not just about fitting boxes in; it is built around vessel safety and operational efficiency. The planner balances many constraints at once.

Container stowage data is usually exchanged between the parties in a standard electronic message known as BAPLIE. It lists each container's slot, number, weight, port of discharge and special attributes such as dangerous goods, reefer or out-of-gauge.

Printed or on-screen bay plans show a cross-section of each bay and are used on the quay to check where a container sits. The final plan, reflecting changes made during loading, is the reference for the ship and subsequent ports.

A container placed in a different slot from the plan can lead to the wrong box being discharged, unnecessary restows, breaches of dangerous goods segregation or a reefer ending up without a power connection.

For that reason, on some operations, particularly with dangerous goods, reefers or heavy boxes, stowage positions are checked against the plan on site. The aim is not to change the plan but to identify discrepancies and report them to the parties concerned.

In container loading supervision, checking stowage positions is usually an optional item covering defined groups of containers. The surveyor compares each box's actual slot with its planned slot and records any differences.

Karan Gözetim provides container loading and discharge supervision from Gemlik; the scope of any stowage check is agreed at the quotation stage.