General cargo, or breakbulk, is cargo shipped as individual units rather than in containers or loose in bulk: bagged rice, cement and fertiliser, steel coils, pipes, plywood, drums, machinery and vehicles. In Indonesia, general cargo ships still carry much of the inter-island trade, especially to ports without container cranes. This guide walks through how to build a practical stowage plan for this kind of cargo.
The cargo spaces: holds, tween decks and hatch covers
A traditional general cargo ship has several holds, each split vertically by a tween deck. The space below the tween deck is the lower hold; its floor is the tank top, which is also the roof of the double-bottom tanks. Above sit the hatch covers, which can carry cargo on the weather deck as well.
The capacity plan gives two volume figures for each space:
- Bale capacity: measured to the inside of frames, beams and stiffeners. Use it for packaged cargo.
- Grain capacity: measured to the shell plating, including the spaces between frames. Use it for bulk cargo that can flow into those gaps.
Every floor also has a permissible uniform load in t/m². The tank top is normally the strongest, the tween deck is weaker and weather-deck hatch covers are the most limited. Floor strength is covered in detail in deck and tank top strength.
Stowage factor and broken stowage
The stowage factor (SF) is the volume one tonne of cargo takes up in its packaging, in m³/t. Broken stowage (BS) is the share of space lost to the shape of the cargo, the hold structure and dunnage. The hold space a parcel needs is:
Space required = weight × SF ÷ (1 − BS)
| Cargo (example) | Indicative SF (m³/t) | Indicative broken stowage |
|---|---|---|
| Bagged cement | 0.9–1.0 | 5–10% |
| Bagged rice | 1.4–1.5 | 5–10% |
| Bagged fertiliser | 1.0–1.2 | 5–10% |
| Plywood in bundles | 1.7–1.9 | 5–15% |
| Drums of liquid | 1.6–1.9 | 15–25% |
| Steel coils | 0.3–0.5 | 30% or more |
These are illustrative ranges. The real SF depends on the packaging and should come from the shipper's data or from measurement. Try the numbers in the stowage factor calculator.
Example: 800 t of bagged rice at an SF of 1.4 m³/t with 10% broken stowage needs 800 × 1.4 ÷ 0.9 ≈ 1,244 m³. If the No. 2 lower hold has a bale capacity of 1,600 m³, about 356 m³ is left for a light, compatible cargo such as bagged sugar, provided the total weight stays within the tank top limit.
It also helps to know whether a parcel "cubes out" (light cargo with a high SF fills the space before reaching its weight) or "weighs out" (dense cargo with a low SF reaches its weight before the space is full). Dense cargo low down with lighter cargo on top often makes the best use of both weight and space.
Tank top and hatch cover loads
The pressure from a heavy item is its weight divided by the bearing area. Take a 24 t machine sitting on two skids of 4.0 × 0.3 m each. The bearing area is 2.4 m², so the pressure is 10 t/m². If the tween deck on this example ship is rated at 4 t/m², the machine cannot go straight onto it. With dunnage beams or a grillage that spread the load over 3.0 × 2.5 m (7.5 m²), the average pressure drops to 3.2 t/m².
Load spreading only works if the dunnage is stiff enough and bears on structural members such as girders and transverse beams. For very heavy items, ask the class society or a naval architect whether a point-load check is needed. The deck load calculator gives a quick first check.
Separation and cargo compatibility
One general cargo hold often holds cargo for several receivers and ports. Parcels are separated with nets, tarpaulins, paint marks, coloured rope or dunnage so stevedores at the discharge port do not mix them up. Planners also check compatibility:
- Wet and dry: cargo that gives off moisture or might leak, such as drums, should not sit above bagged cement, rice or flour.
- Odour and taint: fishmeal, raw rubber or hides can spoil tea, rice and other foodstuffs.
- Dusty and clean: bagged cement and fertiliser are best kept away from clean cargo.
- Heavy and fragile: heavy cargo must never crush cargo that dents easily.
- Dangerous goods: follow the segregation rules of the IMDG Code; see dangerous goods stowage on ships.
Ship's sweat and cargo sweat matter on voyages between cool and hot climates. Hold ventilation and dunnage that leaves air gaps help limit condensation damage.
Discharge order and access
The basic rule: cargo for the last port is loaded first and stowed deepest, while cargo for the first port goes where it is easiest to reach, such as the tween deck or directly under the hatch opening. A wrong order leads to overstowage, where cargo has to be shifted out of the way to reach another parcel, costing time and stevedoring money.
Also plan for:
- Spreading cargo across holds so several gangs can work at once and port stays stay short.
- Heavy items in holds served by ship's cranes or derricks with enough SWL.
- Stability at every port. After part-discharge, KG, draft and trim change; check them with the basic GM calculator and the draft and trim calculator.
- Optional cargo whose discharge port is not yet fixed, stowed so it can come out at any of the options without overstowage.
Dunnage and securing
Dunnage spreads loads, provides drainage and ventilation, separates parcels and adds friction so cargo does not slide. Timber dunnage on international voyages normally has to comply with ISPM 15. Cargo that can shift is secured according to the ship's Cargo Securing Manual and the principles of the CSS Code: chocking, lashing or tomming. The principles of securing are covered in cargo lashing and securing.
Inter-island general cargo in Indonesia
Many inter-island routes, including subsidised ones, carry a mix of cement, rice, building materials, consumer goods and vehicles on a single voyage with several calls. Common challenges include:
- Small ports without shore cranes, so the work depends on ship's gear and stevedore capacity.
- Ports with large tidal ranges and limited depth, where the arrival draft has to be watched.
- Shipper weights that are not always accurate; spot weighing helps check declared parcel weights.
- Weather-deck cargo that needs protection from rain and seas and proper lashing.
For a tidy plan, list the cargo by port, work out volumes with SF and broken stowage, allocate holds, then check deck loads and stability. STOWAGE.ID Vessel Stowage helps shore-side planners build and compare scenarios like this; see also the general cargo stowage page. It is planning and decision support: the ship's class-approved loading computer and stability booklet remain the official reference, and the final decision rests with the master and chief officer.