Packing a shipping container so nothing is ruined when you open it

Think in three dimensions before you carry anything in

A container is long, narrow and taller than it looks. The instinct is to fill from the back wall forwards in a solid mass, and that instinct produces two problems: everything you need is at the back, and the weight ends up wherever it happened to fall.

Before the first box goes in, decide three things.

1. What you will need to reach. Anything you might want in the next six months goes near the doors, full stop.
2. Where the weight goes. Heavy items spread along the length, not concentrated at one end.
3. Whether you want an aisle. A 600 mm walkway down one side costs you maybe a fifth of the floor area and turns an unusable box into a store you can actually work out of.

Sketch it on paper. It takes five minutes and it stops the sequencing mistakes that cannot be undone once forty cartons are stacked in front of the thing you forgot.

Weight distribution, and why it matters more than you would think

Spread the heavy items evenly along the floor. Not because the container cannot take it — a general purpose unit is rated to carry many tonnes — but because of what happens either side of the storage period.

If the unit is ever lifted or moved loaded, an unbalanced load is genuinely dangerous. A crane crew calculates on an assumed centre of gravity, and a load stacked heavily at one end puts the real one somewhere else. Even on the ground, a concentrated mass at one end pushes harder on two of the four pads, which is how a corner settles and the doors stop closing.

The rules are simple:

• Heaviest items on the floor, spread along the length, roughly balanced end to end and side to side.
• Nothing heavy stacked high. A toolbox at chest height is a hazard every time you open the doors.
• Point loads spread with a sheet of ply or a pallet. Machinery on small feet will mark and eventually punch marine plywood.
• Do not stack against the doors. Things settle, and a load leaning on the doors comes out at you.

Get everything off the floor

This is the single most valuable habit in container storage. The floor is the coldest surface in the box, it is the surface any water that gets past a door seal will run across, and it is where condensation ends up.

Use pallets, timber battens, a layer of bearers, plastic crates — anything that lifts the load 50 to 100 mm and lets air pass underneath. Cardboard sitting directly on marine ply wicks moisture out of the timber and out of the air, and that is how the bottom row of boxes turns to mush while everything above it is untouched.

The same principle applies to the walls. Leave a gap of 50 mm or so between the load and the side walls. The walls are steel, they are where condensation forms first on a cold night, and anything pressed against them collects it.

Managing moisture — the real enemy

Most goods ruined in containers are ruined by moisture that came in with the load rather than through the roof. Warm humid air enters when you load, the steel cools overnight, and the moisture in that air condenses on the ceiling and walls and drips back down.

You reduce it at the source:

• Pack dry. Nothing damp goes in — not a garden hose, not a wetsuit, not timber that has been out in the rain, not a lawnmower with wet grass in the deck, and definitely not anything with a fuel tank full of moist air.
• Load on a dry day if you have the choice, and preferably not late in the afternoon in humid weather.
• Use desiccant. Hanging container desiccant bags are cheap and they work. Put them high, where the moist air is, not on the floor.
• Do not wrap tightly in plastic. Sealed plastic traps whatever moisture was inside it against the item. Breathable covers, dust sheets and moving blankets are better for long storage.
• Keep the vents clear. Every general purpose unit has passive vents in the upper side panels. Stacking hard against them defeats the little airflow you have.

Things that should not go in a container at all

• Fuel, gas bottles and anything flammable. A closed steel box in the Australian sun gets very hot. This is a genuine hazard and usually a breach of your insurance.
• Anything perishable. Food, seed, pet food, birdseed. It brings vermin, and vermin bring damage to everything else.
• Batteries left connected. Disconnect and remove where you can.
• Paint and solvents. Temperature cycling ruins them and the fumes concentrate.
• Anything alive, including pot plants. Obvious in hindsight, regularly attempted.

Packing for long-term storage specifically

Six weeks and six years are different jobs. If the container is going to sit, take the extra steps.

Furniture. Dismantle what comes apart. Wrap in moving blankets, not plastic. Stand mattresses on edge against a wall with a barrier between the mattress and the steel, never flat on the floor.

Appliances. Drain fridges and washing machines completely and leave doors ajar with a wedge. A sealed wet fridge becomes a science experiment.

Tools and machinery. Wipe down with an oily rag or spray with a corrosion inhibitor. Bare steel in a humid box will bloom with surface rust in a season.

Documents and photographs. Archive boxes, on pallets, in the middle of the stack rather than against a wall. Add desiccant to the box itself.

Electronics. Original boxes if you have them, desiccant inside, and keep them off the floor and away from the walls.

Fabric, leather and anything upholstered. These take up moisture readily. Breathable covers and desiccant, and check them at the first opportunity.

Label like you will forget, because you will

Number every carton and keep a list on your phone with the number and the contents. Write on two faces of each box, one of which faces the aisle. Keep a rough map of what is where in the container, and put a copy of it in a sleeve taped inside the door.

Eighteen months later this is the difference between fetching one thing in five minutes and unloading half the container onto the lawn.

Security and the load

Pack so nothing valuable is visible in the first two metres. Anyone who gets the doors open takes what is at the front, and what is at the front is what they can carry. Bikes, tools, outboards and anything else easily resold belong at the back, behind the boring boxes.

Put the door end where you can see it from the house or the office, and keep the doors away from a boundary fence or a lane if you have the choice.

Check it after the first big weather

Open the doors after the first heavy rain and the first hot spell. You are looking for three things: water on the floor near the doors, which points to a seal or a level problem; drips or staining on the ceiling, which is condensation rather than a leak; and any sign of vermin.

Catching any of those in the first month lets you fix it while the load is still worth saving. Discovering them in year two does not.

The grade you packed into matters

All of this assumes the container itself keeps weather out. New and cargo-worthy units are checked wind and watertight before leaving the yard, and they are the grades to use for anything that must stay dry. Units sold as-is are not sold watertight — they are a good buy for steel, fencing, formwork and scrap, and a poor place for anything you would be upset to lose. The grades page sets out the difference.

If you are not sure whether what you are storing suits the unit you are looking at, describe the load when you ring. That conversation takes two minutes and it is the cheapest insurance available. Ring 1300 467 776, or read the storage page for how we set units up for long-term use.