Guides / Modular buildings
The supplier list you are choosing from is not a list of factories. It is a mix of factories, assemblers and trading companies, most of them describing themselves the same way. Seven checks separate them, and six of those checks can be run from your desk in an afternoon.
Ask what the supplier actually makes, not what it sells. A container house is three products assembled into one: the steel frame, the sandwich panel, and the fittings and finish. Whoever cuts and welds the frame controls your structural quality; whoever forms the panels controls your thermal and fire performance; whoever assembles controls the tolerances you will see on site. A supplier that owns one of those three and buys the other two is still a legitimate partner, as long as it says which is which.
The fastest test is a technical question with an operational answer, asked in writing: what changes on your panel line if I move from a 50mm core to a 75mm core on the same unit type. A producer answers with the line, the run length, the effect on price and the effect on lead time. A company that only resells forwards the question and returns a number.
A factory cuts steel, welds frames on a jig, forms and cuts panels, and runs coating or galvanising before assembly. An assembler buys frames and panels to its own drawings and builds the unit, which is a real production capability even though the parts arrive made. A trading company coordinates all of it and owns none of it.
None of those three is automatically the wrong choice. What matters is that you know which one you are talking to, because the failure modes differ. A factory can change a weld procedure, but may be inflexible on small quantities or unusual finishes. An assembler can move quickly on a custom layout, and depends on its panel supplier for the specification you asked for. A trader can compare several factories and absorb your paperwork, and cannot fix a tolerance problem without going back to someone else.
The costly mistake is believing you are buying from a factory when you are buying from a trader, then discovering it during a dispute over a panel that was not the thickness you ordered.
Each one yields something you can keep in the order file, which is the point: a claim in a chat is not evidence.
| Check | Question to ask | A real answer contains |
|---|---|---|
| 1. Production video | Send a two-minute video of this unit type in production, with the drawing revision visible | Your unit type, a dated frame, a visible drawing or part mark. Generic showroom footage is not an answer |
| 2. Frame ownership | Who cuts and welds the main frame, and what gauge and corner post section is used | A process answer, not a number: cut to length, jig, weld, then galvanising or coating |
| 3. Panel source | Which panel core and thickness, from which line, and what test report covers it | Core type, density, thickness range, and a report with a number you can check |
| 4. Business licence | A copy of the licence, and whether the registered scope covers production of this product | A scope line that matches what you are buying, not a general trading scope |
| 5. Export capability | Is the order exported in the supplier's own name, and who handles the documents | Clarity on who the shipper is, which decides who you can claim against |
| 6. Inspection | Will you accept a third-party pre-shipment inspection on a first order | Yes, plus a checklist agreed before production starts |
| 7. Loading plan | How many units fit a 40HQ on this packing arrangement, with a drawing | A packing drawing. This is also where the minimum order quantity comes from |
The loading plan question is covered in more detail in what sets the MOQ for container houses, because the arithmetic behind a minimum and the arithmetic behind a freight cost are the same arithmetic.
Four documents carry most of the weight on a first order. Ask for them in this order, because each one narrows the next.
Ask for the documents with the quotation rather than after the deposit. A supplier that produces them at quotation stage is organised; one that produces them three weeks after payment is improvising, and improvising is the thing you are trying to screen out.
Our own certifications page lists what we hold and what we do not, and the guide to modular building certifications explains what each one actually covers, including the ones buyers ask for that do not exist as a single certificate.
A quotation without a drawing. A unit price that arrives before a layout, a panel specification and a destination port is a number without a subject. It cannot be compared with any other quote, and it will change.
A single MOQ figure with no arithmetic. Minimum quantities follow the loading plan and the panel run. A number quoted as policy, identical for every buyer and every port, is a sales position rather than a production constraint.
A price below the panel cost. Panel and steel are the two largest inputs. If a quotation is far under the others, one of three things is happening: a thinner panel, a lighter frame, or a specification that will be substituted later. Ask for the panel thickness and the frame gauge in writing, and measure on arrival.
Refusal of a third-party inspection on a first order. This is the cheapest risk control available to you and the one a confident supplier welcomes.
Silence on who the manufacturer is. A trader is entitled to exist. A trader that cannot or will not name the production site it is using is asking you to take on a risk it will not describe.
Sequence matters more than any single clause, because each step gives the next one something to check against.
The same sequence applies to a flat-pack order and to a detachable unit; what changes is the packing arrangement in step two, which is why flat-pack and detachable container specifications are published separately rather than merged into one page.
We are an engineering-led supplier rather than a single-site factory, and it is worth stating plainly because it is exactly the question this page tells you to ask. Manufacturing, testing and consolidation for our orders are carried out by partner facilities in China, working to drawings we issue and inspect against. That means the drawing, the specification and the inspection checklist are ours, and the production site is not.
If your requirement is that the supplier must own the welding line, we are not the right partner and we would rather say so before a deposit than after one. If your requirement is that somebody owns the specification, the inspection and the paperwork end to end, that is the model we work in, and the inspection process describes how it is controlled.
Is every container house supplier in China a manufacturer? No. The word covers a factory that cuts and welds the frame and forms the panels, an assembler that buys those parts and builds to order, and a trading company that coordinates without owning production. All three can deliver a good building; only the first can change a weld procedure on its own authority.
How do I confirm a supplier actually makes the frame? Ask for a video of your unit type in production with a drawing revision visible, and ask who cuts and welds the main frame. A maker describes a process. A reseller describes a product.
Which documents are worth asking for? Business licence with the registered scope, export licence if the order ships in the supplier's name, the quality certificate checked against the issuing body's register, and the panel and steel test reports for the specification you ordered.
What deposit structure is normal? A deposit against production and the balance against shipping documents. What matters more is what the deposit releases: an approved production drawing, a dated schedule and an agreed inspection point.
Can I inspect before shipment? Yes. Agree the checklist before production, book a third-party inspection at pre-shipment, and keep the report with the shipping file.
What is the fastest way to tell a trader from a factory? Ask what changes on the panel line when the core goes from 50mm to 75mm on the same unit. The answer separates the two in one exchange.