Lashing and securing keep cargo from shifting, sliding or tipping during road and sea transport. The idea is simple: the forces created when a truck brakes or a ship rolls must be absorbed by a mix of blocking, bracing, lashing and friction. This guide covers the CTU Code principles, the design accelerations and a simple worked example.
Core principles of the CTU Code
The Code of Practice for Packing of Cargo Transport Units (CTU Code) was published by the IMO, ILO and UNECE in 2014 (IMO circular MSC.1/Circ.1497). It applies to containers, trucks and other transport units. The principles used most often:
- Secure cargo against forward, backward, sideways and upward forces.
- Fill or block voids: cargo that can move even a little gains momentum and damages itself and the container walls.
- Keep heavy items low and the centre of gravity central; see centre of gravity and weight distribution.
- Never exceed the capacity of the container's or vehicle's lashing points.
Design accelerations by mode
The CTU Code expresses design accelerations as fractions of g. The values commonly quoted from its tables are below; always check the current edition.
| Mode / area | Longitudinal (forward) | Longitudinal (backward) | Transverse (sideways) |
|---|---|---|---|
| Road | 0.8 g | 0.5 g | 0.5 g |
| Sea, area A | 0.3 g | 0.3 g | 0.5 g |
| Sea, area B | 0.3 g | 0.3 g | 0.7 g |
| Sea, area C | 0.4 g | 0.4 g | 0.8 g |
Truck braking (0.8 g forward) is often the governing case lengthwise, while rolling in open ocean (area C) governs sideways. A container stuffed in Cikarang and shipped to Europe has to be safe for both. For calculating securing forces on the road, Europe uses the standard EN 12195-1.
Four ways to restrain cargo
Blocking means holding cargo against something rigid: the container walls, other cargo, timber beams or empty pallets. It is the most effective method because its capacity is high and does not depend on lashing tension.
Bracing is blocking with angled or cross-wise supports, such as timber nailed to the container floor or built up between cargo and wall.
Lashing uses web straps, chains or wire rope attached to lashing points. Direct lashings connect the cargo to the lashing points; top-over lashings press the cargo down onto the floor and increase friction. Capacity is shown as MSL (maximum securing load) or lashing capacity (LC) on the label, usually in daN (1 daN = 10 N).
Friction between cargo and floor helps resist movement. As a guide, friction mats are commonly around µ 0.6 and dry wood on wood about 0.3–0.5; verify against the CTU Code annex. Small voids are filled with dunnage such as dunnage bags, timber or filler cartons.
Dunnage, airbags and palletised cargo
Most Indonesian export loads are cartons on pallets rather than heavy crates, and for those the key is closing the voids:
- Dunnage bags (airbags) go into gaps between pallets or near the doors and are inflated to the manufacturer's pressure. They should not be the only restraint in front of the doors and must be kept away from sharp edges.
- Timber or frames handle large gaps, for example at the door end when the last row is not full. Export timber must comply with ISPM 15.
- Stretch wrap and strapping bind cartons to the pallet so each pallet moves as one unit. They do not replace blocking inside the container.
Stow pallets tight against the front and side walls. Spread any remaining transverse gap in the middle of the container rather than leaving it on one side.
Worked example: a 2,000 kg crate in a 20GP
Assumptions (simplified for illustration):
- Wooden crate of 2,000 kg, base 1.2 m (lengthwise) × 1.0 m (across), height 1.8 m.
- Centre of gravity in the middle, 0.9 m above the floor.
- Friction wood on timber floor µ = 0.3; with a friction mat µ = 0.6.
- Vertical component taken as 1.0 g. The CTU Code tables give vertical values per mode; check the current edition.
- g = 9.81 m/s².
1. Sliding force to restrain: F = m × g × (c − µ × 1.0).
| Direction and case | µ 0.3 | µ 0.6 (friction mat) |
|---|---|---|
| Forward, road (0.8 g) | 9.81 kN | 3.92 kN |
| Sideways, road (0.5 g) | 3.92 kN | 0 (friction suffices in theory) |
| Sideways, sea area C (0.8 g) | 9.81 kN | 3.92 kN |
For example: 2,000 × 9.81 × (0.8 − 0.3) = 9,810 N ≈ 9.81 kN (about 981 daN).
2. Tipping risk: in simple terms, the crate tips when c × h exceeds half the base width (with a vertical component of 1.0 g).
- Sideways, road: 0.5 × 0.9 = 0.45 < 0.5. Stable.
- Sideways, sea area B: 0.7 × 0.9 = 0.63 > 0.5. Tips unless secured.
- Sideways, sea area C: 0.8 × 0.9 = 0.72 > 0.5. Tips unless secured.
- Forward, road: 0.8 × 0.9 = 0.72 > 0.6 (half of 1.2 m). Tips forward.
3. Solution: block the crate against the front wall up to its top edge (not only at floor level), add a friction mat, then fit two direct lashings per side. Assume each lashing has an MSL of 10 kN and is set at 30° both vertically and horizontally; its sideways contribution is roughly 10 × cos 30° × cos 30° = 7.5 kN. Two lashings give 15 kN, more than the 3.92 kN needed with the mat, and they also resist sideways tipping.
This is an educational simulation. For real cargo, use the full methods in the CTU Code annex or EN 12195-1 and the Lashing Calculator. A plan is no substitute for a lashing survey, carrier instructions or operator approval.
Lashing in containers and trucks
Dry containers have lashing points on the bottom and top rails and at the corner posts. Their capacity is limited, often far below that of a heavy lashing, so check the markings or ask the equipment owner. Flat racks and open tops have stronger points; see the flat rack container guide. Indonesian trucks, whether dropside or wingbox, often have non-standard tie-down points; do not assume European ratings. Cargo that shifts also changes the axle load, so check it with the Axle Load Calculator.
Common mistakes
- Relying on friction alone, especially for heavy cargo on slippery or wet timber.
- Blocking only at floor level for tall cargo that is actually at risk of tipping.
- Mixing devices with different MSL ratings without accounting for the weakest component.
- Lashing to points never designed for it, such as roof bows, tarpaulin rails or machine piping.
- An empty space at the door end with no restraint, so cargo falls against the doors on opening.
- Slack lashings after a long road leg with no re-tensioning check.
Next steps
Lay out the cargo and spot the voids to fill in the 3D Load Planner, then size the lashings with the Lashing Calculator. For the wider picture of where containers sit on board, read what is a stowage plan.