Two containers can look almost identical in a photograph and be several thousand pounds apart in price. The difference is condition, and condition in the container trade is described by a small set of grades that are widely used but not legally defined. Understanding what those grades actually mean — and what they do not promise — is the fastest way to avoid overpaying for a unit you do not need, or underpaying for one that will not do the job.
Where used containers come from
Shipping containers are built to move cargo across oceans for around ten to fifteen years. After that, the economics of shipping them back empty stop working, and they are sold off in the countries where they happen to have ended up. Because the UK imports far more than it exports, a steady surplus of containers reaches British depots every year. That surplus is the used market.
A “new” container in the UK is almost never brand new in the sense of never having been used. It is a one-trip unit: built in Asia, loaded once with cargo for its delivery voyage, and sold on arrival. It has done a single journey and looks essentially new.
The grades explained
New / One-Trip
Manufactured within the last year or two and used for a single laden voyage. Paint is clean and uniform, there is no meaningful rust, the floor is unmarked marine plywood, the door seals are supple and the locking gear moves freely. One-trip units usually come in a solid factory colour and often have cargo doors that still shut with a satisfying clunk.
Buy one-trip if appearance matters (a container visible from a house, a shop or a client-facing site), if you plan to convert or modify the unit, or if you want the longest possible service life. Expect to pay the most.
Cargo-Worthy (CW)
A used container that remains structurally sound enough to be certified for international shipping. In practice that means no through-holes, sound floor and door gear, functioning seals, and corrosion that is cosmetic rather than structural. It will show its age: surface rust, dents, patched repairs and the ghost of a previous shipping line’s paintwork.
Cargo-worthy is the sweet spot for most buyers who want a container that will last decades but do not need it to look new. It is the grade to specify if there is any chance the unit will be shipped, moved between sites repeatedly, or stacked.
Wind & Watertight (WWT)
The workhorse grade for UK storage. The container is dry inside and secure, with a sound roof, working doors and no holes — but it is no longer certified for shipping. Structural repairs, heavier corrosion, floor patches and cosmetic damage are all acceptable within the grade, provided the unit keeps weather out.
WWT is what most people should buy for a farm yard, a builder’s compound, a domestic store or an allotment. It does the same practical job as a cargo-worthy unit at a lower price, and the difference is largely paperwork and appearance.
As-Is
Sold with its faults declared. That might mean a hole in the roof, a door that will not seal, a rotten floor section, or damage from a forklift. As-Is units are bought by people who intend to cut them up, use them as static shells where weatherproofing is irrelevant, or carry out their own repairs. If you are buying As-Is, get the specific defects listed in writing before you pay.
What the grades do not tell you
Grading describes condition, not age, colour or specification. Two wind-and-watertight 20ft containers can be eight years apart in age and still carry the same grade. Grades also say nothing about:
- Colour. Used containers arrive in whatever the last operator painted them. If you need a specific colour, you are buying a one-trip unit or paying for a respray.
- Floor treatment. Marine plywood floors in shipping containers are treated with insecticide as a biosecurity requirement. This matters if you are storing food, animal feed or bedding — ask, and consider overboarding.
- Previous cargo. Reputable depots reject contaminated units, but if you are storing anything sensitive, inspect and ventilate.
- Insulation or condensation control. No standard container is insulated. A steel box in a British winter will sweat. If you are storing anything moisture-sensitive, look at insulated containers or budget for lining and vents.
Condensation: the thing nobody warns you about
“Container rain” is the most common complaint from first-time buyers, and it is almost never a fault. Warm, damp air enters the container during the day; at night the steel cools faster than the air, moisture condenses on the underside of the roof, and it drips. The container is watertight — the water came from inside.
The fixes are straightforward: keep the unit raised and ventilated, add extra vents if the standard ones are inadequate, avoid storing anything wet or freshly cut, and consider insulating the roof if you are storing tools, documents or electronics. Getting air moving is worth more than any dehumidifier.
Which grade should you buy?
A practical way to decide:
- General storage on your own land, appearance not critical — wind and watertight. This is the right answer for most buyers.
- Storage where the container is on show, or a domestic setting — one-trip, or a repainted cargo-worthy unit.
- Conversion into an office, workshop, gym or garden room — one-trip. You are about to spend money on cutting, insulating and fitting out; do not build it on a corroded shell. See modified containers for units already converted.
- Repeated transport, stacking or export — cargo-worthy at minimum.
- You need a shell to cut up — As-Is, with the defects listed.
Questions worth asking before you buy
Ask what grade the unit is sold as and get it in writing on the invoice. Ask its year of manufacture if that matters to you. Ask whether photographs are of the actual unit or a representative example — for used stock, representative photographs are normal and honest suppliers say so. Ask about the floor and the door seals specifically, because those are the two things that most affect day-to-day use.
Finally, remember what “satisfactory quality” means for second-hand goods under UK consumer law: it is judged against the age, price and grade the unit was sold as. Surface rust and dents on a wind-and-watertight container are characteristics of the grade, not faults. A hole in the roof on the same unit is a fault. Our Returns Policy explains how we handle both.
Grade is only half the decision — size and access decide the rest. See what size shipping container you need and our guide to delivery access and ground preparation.
Our Condition Guide sets out the grades we sell against in full detail, and the FAQ answers the questions we get asked most. Browse shipping containers and storage containers, or ask us for a delivered price and tell us what the container is for — we will say honestly which grade will serve you best.