What a Worker Accommodation Quotation Does Not Tell You: Nine Material Differences

Two quotations for the same worker accommodation block can describe an identical building in words, differ by a third in price, and differ by roughly half in the amount of steel, zinc, floor board and hardware that will actually arrive — and the only one of those differences a buyer can prove without a laboratory is the weight.

This is the least comfortable subject in this industry, and it is the one a farm buying accommodation at volume most needs. The specification sheets look the same because they are written from the same template. The dimensions are the same because they are set by the shipping container. The photographs are the same because they are renders. What is not the same is what is inside the wall.

This article sets out the nine items where the difference lives, the one number that settles the argument, the six failure modes that follow from a low-cost configuration, and the three requirements that are specific to worker accommodation on a farm. It is written from our own standard configuration, and the comparison column is the low-cost practice that is common in this market rather than a claim about any named competitor. Where a buyer can check something, the article says how.

Why the quotes look identical

A modular building is bought as a building and delivered as a stack of materials. The buyer sees the building; the price is driven by the stack. Everything between those two facts is where the difference hides, and there are four reasons it stays hidden.

• The specification is copied. Most quotes are written from a template that says "sandwich panel", "steel frame" and "aluminium window" without a single number attached to any of them.
• The number that is quoted is not the number that is delivered. Profile thickness is routinely stated at the top of a range and shipped at the bottom. A quote that says 2.1 mm and a delivery at 1.45 mm are the same document.
• The visible items are not the expensive ones. The panel colour, the door and the window are the parts a buyer inspects. The corner block, the zinc weight and the floor board grade are the parts that decide the service life.
• Nobody weighs the building. This is the one that can be fixed in an afternoon, and it is described below.

The nine items where the difference actually lives

The middle column is our standard configuration. The right-hand column is the low-cost configuration that is common in this industry. Every row is something a buyer can put in a written question and expect a written answer to.

Unit weight: the number that ends the conversation

Every row above can be argued about in a meeting. Only one of them can be measured in five minutes by a third party, and it is the total.

Two modules of the same nominal size, one at 1.3 tonnes and one at 0.85 tonnes, do not contain the same building. The difference in mass comes from profile thickness, zinc coating, flooring grade and hardware, in that order of contribution. For visually similar units the actual material content differs by roughly 1.4 to 1.6 times.

That is why comparing prices alone cannot tell a buyer which quote is cheaper. The lighter unit costs less to buy and less to ship, and it is more expensive to own, because every kilogram removed was removed from something that had a job: on a wet site it came out of the zinc, on a relocatable camp it came out of the joint hardware, on a cold highland site it came out of the insulation.

The way to use this in procurement is straightforward. Ask for the unit weight in the quotation. State in the purchase order that a pre-shipment inspection will include weighing one unit. Then do it. A supplier who is honest about the frame will not object, and a supplier who is not will withdraw the offer — which is the outcome the test is for.

Six failure modes that follow a low-cost configuration

These are the patterns we see when a buyer asks us to match a price rather than a specification. They are worth reading as a checklist, because each one can be verified before a deposit is paid.

1. Overstated thickness. Quoted at 2.1 mm and supplied at 1.45–1.8 mm, so the actual load capacity does not match the design assumption — and on a two-storey block that assumption is carrying a floor of people.
2. Non-standard shrunken sections. A "50×100" tube that measures 48×98 weakens the structure and the fittings, and it causes fit-up problems during installation — which appear as a programme delay, not as a material complaint.
3. Black iron corner blocks. With no zinc layer the joints rust first. They are the weakest point of the building for both load transfer and corrosion, and they are the item that decides whether the block can be dismantled and re-erected at all.
4. Low-grade colour coil. A 5–10 g zinc layer and an 8–10 miu coating produce rust spots, paint loss and colour mismatch within a short time. On a red-earth farm the mismatch is visible from the gate.
5. Recycled powder coating. Neither film thickness nor adhesion is assured, the risk of fading and chalking is high, and the warranty period is hard to verify afterwards.
6. Grade B flooring and salt migration. Salt migration corrodes the frame from the inside and the damage is irreversible. Non-standard screws rust and snap, which hampers later maintenance and re-assembly.

Three requirements that are specific to worker accommodation

The nine items above apply to any container building. On a labour camp three more sit on top of them, because the building is used intensively by people who did not choose it.

Cleanability. A room that has to be turned around between crews needs a hard floor, a washable wall and a bed that strips quickly. This is a specification choice, and it is the one most often lost when a hospital or hotel template is reused for staff housing.

Peak water. Accommodation draws in bursts — a shift ends and everyone showers at once. The wet-core strategy, the storage volume and the pipe sizing have to answer the peak rather than the average, and the building has to be structurally designed for wherever the tank ends up.

Insect and dust control. This is the difference between a block that is habitable in week one and one that is complained about by week three. Screens specified with the window, envelope joints detailed as continuous, and a door closer — three cheap items that decide the interior environment.

What customisation actually covers

Customisation in this industry is often presented as unlimited and delivered as a colour choice. What a factory can genuinely change on a project basis is a finite list, and knowing it makes the enquiry productive rather than a negotiation about what is possible.

• Dimensions. The folding container is normally 5950×3000×2800 mm and the flat pack container 6000×3000×2840 mm; length, width and height can all be built to project-specific dimensions.
• Corrosion system. Any double-sided zinc coating thickness up to 300 g, and 4.0 mm profiles on request.
• Wall panels. 50, 75, 100, 150 or 200 mm thicknesses, with core options of rock wool, glass wool, EPS, PU, PIR, glass-magnesium board and phenolic, and density adjustable within the permitted range.
• Colour and finish. Powder coating colours are selectable, which is how a farm gets a red panel with a white frame rather than a white box.
• Openings and hardware. Door and window sizes are customisable, including the insulated window made as a custom model for the flat pack range; door, window and bottom-tube quantities can be adjusted to the project.
• Flooring. Glass-magnesium and cement-sanded boards at 15 or 18 mm, cement board at 18 mm, and other thicknesses on request.

What a factory can and cannot put its name to

A factory can hold itself to a drawing. It can guarantee frame thickness, zinc weight, floor grade and hardware specification, open its doors for inspection, and supply the certificates and test reports those claims depend on. It can tell a buyer honestly when a request needs a different product.

It cannot certify a building against a code it does not administer. Structural calculations for the site, the fire strategy, means of escape, occupancy limits, accessibility, foundation design and permits belong to the buyer's engineer, the operator's health and safety responsibility and the local authority.

The useful question at enquiry stage is not "can you handle everything" — anyone will say yes — but three specific ones: which documents will you give my engineer, which drawings do you need back from them before you cut steel, and what is the unit weight we should expect on the weighbridge.

Questions buyers ask when comparing quotations

The specification is the only document that survives the delivery

A quotation is a commercial proposal. A specification is what gets built. On a worker accommodation order the practical difference between the two is a page of numbers, and that page is the only thing that will still be enforceable six months after the invoice is paid.

The block in these photographs is built from the same module family, in the same factory, on the same lines as the unit standing on the yard apron. It is not a showcase product. It is what the system produces when the nine items above are written down and the factory is held to them — which, on a farm buying beds by the hundred, is the whole of the argument.

Global Container (Suzhou) Co., Ltd. produces prefabricated container house, flat pack container house and detachable container house systems at Zhenze Town, Wujiang District, Suzhou, Jiangsu, China, with two thousand detachable and three hundred expandable units a month of capacity and exports to more than thirty countries since 2012. Detailed configuration lists, material samples and test documents are available on request, and we can prepare a tailored configuration for a specific project.