Real thickness against declared thickness: a buyers' checklist for container houses

In a modular housing purchase there is an uncomfortable asymmetry: the buyer cannot see the steel once it is painted. What is declared in the quotation and what lands at the port can be two different things, and the difference only shows in the second winter, when corrosion starts at the joints. These are the checks that can be made before signing.

1. Profile thickness — the most inflated number

Our main frame profiles are 2.2 / 2.45 / 2.75 / 3.0 mm, with 4.0 mm on request, all measured actual thickness. Low-cost market thicknesses are typically 1.45 / 1.8 / 1.95 / 2.1 mm, and the declared figure is often higher than the real one.

Verification is simple: callipers on a profile section, in front of the inspector, or on the visible section at the anchor zone. A manufacturer who will not allow measurement in the factory has already answered the question.

2. Zinc coating — what decides service life in humid climates

Our standard applies hot-dip galvanising at 60 g both faces, customisable up to 300 g both faces. The low-cost reference is 40 g. In a coastal or permanently humid environment, that difference separates a unit that lasts from one that rusts in the first years.

3. Corner blocks — galvanised, not black iron

On folding containers, galvanised corner blocks of 3.5 mm and 4.0 mm are standard; on flat pack, both top and bottom corner blocks are 4.0 mm galvanised. Low-cost practice is black iron at 3.0 / 3.2 mm on folding units and 3.2 / 3.5 mm on flat pack. The corner block is where water enters and where the crane lifts: it is not a detail.

Module components: frame, floor joists, sandwich panel, ceiling and perimeter trim.

4. Square tubes and tolerances

All our top and bottom tubes meet national standard: main tube from 1.2 mm, 50×50 top tube from 1.5 mm, the rest from 1.0 mm. Low-cost units start at 0.8 mm on the lower main tube and 1.2 mm on the 50×50 top tube, with out-of-tolerance sections — a “50×100” that actually measures 48×98.

5. Pre-painted steel coil

Wall panels, roof sheet and ceiling sheet use “Traffic White” pre-painted coil from Zhejiang Huada, 0.3 to 0.6 mm, 20 g zinc and 18 miu weather-resistant PE coating: more than eight years of service life. Low-cost coil runs 5 to 10 g zinc and 8 to 10 miu coating, prone to oxidation.

6. Powder coating, floor and hardware

Values for our standard quotation configuration; actual supply is subject to contract and approved drawings.

Finished unit in the hall before packing — thickness measurement and weighing happen at this stage.

What we ask buyers to check themselves

• Weigh a complete unit on a bridge. Weight is the sum of all material and cannot be simulated.
• Measure profile thickness at three points on the frame.
• Ask for the steel coil certificate and compare zinc grammage with the offer.
• Check the floor board: grade, brand and asbestos-free certificate.
• Request the wind resistance report and the panel fire certificate.

If a supplier provides all five, price comparison becomes a real comparison. If not, the lowest price has already explained itself.