A shipping container needs very little looking after, but the little it needs matters. Keep it level, keep water off the roof and touch up the coating before rust bites, and a used unit will still be working in twenty years.
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A simple maintenance schedule
| Interval | Task | Why |
|---|---|---|
| Monthly | Open both doors fully and close them again | Keeps gaskets from sticking and reveals any change in door alignment early |
| Quarterly | Clear leaves and debris from the roof and the top rails | Standing water and trapped organic matter is the number one cause of roof corrosion |
| Quarterly | Grease the cam bars, hinges and lock rods | Seized locking gear is the most common avoidable failure |
| Every 6 months | Check vents are clear and inspect for damp inside | Blocked vents cause condensation and rot in the plywood floor |
| Annually | Walk the outside and touch up any broken paint | Coating is what keeps the steel stable; bare metal is where pitting begins |
| Annually | Check the unit is still level across both diagonals | Ground settles. A racked container will bind its doors and eventually leak |
| Every 5 years | Consider a full clean down and repaint | Far cheaper than repairing corrosion, and it protects resale value |
Rust: what matters and what does not
Containers are built from Corten weathering steel, which is designed to develop a tight surface oxide layer that then slows further corrosion. Light orange surface rust on a used container is normal and largely cosmetic. What matters is whether the coating has been breached and moisture is now sitting on bare metal.
The test is simple. Run a screwdriver or a wire brush over the area. If the rust brushes off and leaves sound steel, clean it, prime it with a zinc-rich primer and topcoat it. If the metal is flaking in layers or pitted deeply enough to feel, it needs a welded patch plate rather than paint.
Priority order for touching up: roof first, then the top rails, then the door frames, then the lower side panels and the floor bearers underneath.
Controlling condensation
Almost every complaint about a leaking container turns out to be condensation. Warm, damp air enters when the doors are open, then the steel cools overnight and the moisture forms on the inside of the roof and walls before dripping onto whatever is below. It is often called container rain.
- Add vents. Two passive vents are standard. Four to six makes a real difference in a unit used for tools, textiles, paper or electronics.
- Get goods off the floor. Pallets or battens allow air to move underneath and stop moisture wicking into cardboard.
- Leave air gaps. Keep stacked items a couple of inches clear of the walls rather than pressed against cold steel.
- Use desiccant. Hanging moisture absorbers are cheap and genuinely effective in a sealed unit.
- Insulate if it matters. Closed-cell spray foam on the inside of the roof and walls removes the cold surface entirely and is the permanent fix.
- Store dry. Never load damp timber, wet equipment or fresh concrete products into a sealed container.
Doors, gaskets and locking gear
The doors are the only moving part and the only place water can realistically get past a sound shell. Grease the cam bar bearings, the hinge pins and the lock rods with a marine or lithium grease a few times a year. If a cam bar needs force, do not force it: check the container is level first, because a racked frame is almost always the underlying cause.
Gaskets should be supple and continuous all the way round. Flattened, split or perished rubber is inexpensive to replace and worth doing as soon as you notice it. A smear of silicone grease keeps the rubber flexible and stops it bonding to the frame in cold weather.
The roof is the weak point
Container roofs are not designed to be walked on or to hold standing water for years. They are also the surface nobody looks at. Sweep leaves and silt off quarterly, check that water runs off rather than pooling in a dent, and if you find a low spot, either pack the container to a very slight fall or fill and coat the depression.
If you must walk on the roof, keep to the perimeter above the rails and spread your weight across a board.
Looking after the floor
The floor is marine-grade plywood over steel cross-members. It is tough, but it is still timber. Sweep it out regularly, deal with spills quickly, and avoid dragging sharp steel across it. Rot almost always starts at the door threshold where rain blows in, so check that area first when you inspect.
If you are storing something heavy on a small footprint, spread the load with a steel plate or timber bearers. The published payload figure assumes evenly distributed weight.
Need a unit that is already sorted?
We can supply containers shot-blasted and repainted, fitted with additional vents, or insulated and lined before delivery, so the maintenance clock starts from zero.
Maintenance questions answered
On land, twenty to thirty years is a realistic working life for a used unit that is kept level, kept clear of standing water and touched up when the coating breaks. One-trip units start that clock much later.
Usually it is condensation rather than a leak. Check on a dry day: if water appears without rain, it is condensation. Add vents, lift goods off the floor and use a moisture absorber. If daylight shows through anywhere with the doors shut, that is a genuine leak.
Clean back to sound material, prime with a zinc-rich or red-oxide metal primer, then use a direct-to-metal topcoat or a marine enamel. Avoid ordinary emulsion or masonry paint, which will not adhere or last.
Yes, at a sensible distance. Very close, high-pressure work will strip loose coating, which is fine if you intend to repaint but not if you want to leave the paint intact.
It arrives treated and does not need routine treatment. If you want extra protection, a floor paint or sealer works well, and a rubber matting layer is worth it under vehicles or heavy plant.
Nine times out of ten the container has settled out of level. Check the diagonals, re-level using packers under the corner castings, and the doors will usually realign. If they still bind, the frame may be racked and needs professional attention.
Remove loose and flaking material with a wire brush or an angle grinder with a wire cup, then prime immediately. Do not leave bare steel exposed overnight, especially in damp weather.