5 Questions Buyers Must Ask Before Signing a Steel Building Contract

Meta description: Most steel building problems start with the wrong questions asked too late. Here are the 5 questions that expose supplier quality and design capability before you commit.

Category: Case Study

Tags: steel building contract questions, prefabricated steel building buyer guide, steel structure supplier selection, steel warehouse procurement Africa South America, steel building quality checklist

5 Questions Buyers Must Ask Before Signing a Steel Building Contract

Most problems with prefabricated steel buildings are decided before a single column arrives on site. They are decided in the contract stage — or more precisely, in the questions that were not asked during the contract stage.

We have been involved in enough post-delivery disputes, site remediation jobs, and "why does the roof leak" investigations to know what the warning signs look like. And almost every time, the warning was available before the purchase. The buyer simply did not know what to ask.

These five questions will not catch every problem. But they will expose the majority of them.

Question 1: "Can I see the structural calculations, signed by a licensed engineer?"

This is the single most diagnostic question on the list.

A supplier who provides a structural drawing is providing a visual representation of a building. A supplier who provides structural calculations — load cases, section properties, deflection checks, connection design — is providing evidence that someone qualified has verified that the building will stand up under the loads it will actually experience.

In many export markets, this distinction is not well understood. Buyers receive architectural drawings, perspective renders, and floor plans, and assume that structural engineering has been done. It may not have been.

Ask for the calculation pack. It will typically run 20 to 60 pages for a standard single-span warehouse. It should include the design wind speed used (expressed in metres per second or kilometres per hour, site-specific), the imposed roof load, the steel grade of every main member, and the governing load combinations. If the supplier cannot produce this document — or produces a one-page summary with no derivations — treat it as a significant risk signal.

On our export projects, structural calculations are standard deliverables. For projects in coastal Mozambique, northern Brazil, and the Atacama-facing zones of Chile, the wind speed and corrosion category inputs vary materially from an inland Chinese reference site. A calculation based on a domestic reference climate and applied to a cyclone-zone site is not a structural calculation for that site.

Question 2: "What steel grade are the main columns and rafters manufactured from, and do you have mill certificates?"

Q235 and Q345 (or its current equivalent Q355) are the two structural grades used in the overwhelming majority of Chinese-manufactured portal frame buildings. The difference in yield strength is roughly 35%. On a heavily loaded building — wide span, heavy roof, crane loading — the choice of grade affects member sizes, weight, and cost.

The problem arises when a supplier quotes Q345 and delivers Q235. This happens. It is not always deliberate — it can be a procurement or production control failure — but it happens, and the delivered building has less structural capacity than the one you bought.

Mill certificates are the paper trail that connects specific steel coils to specific rolling batches to specific chemical and mechanical test results. Ask for them before shipment. Match the heat numbers on the certificates to the markings on the steel. If a supplier resists providing mill certificates as a standard part of the delivery package, ask why.

Question 3: "What is the design life of the corrosion protection system, and what surface preparation standard are you using?"

A steel building in a temperate climate with a standard paint system will last 15 to 25 years before requiring a full repaint. A steel building in coastal West Africa or coastal Brazil with the same paint system may require remedial work within five years — not because the paint is poor, but because the environment was not accounted for in the specification.

Corrosion protection is specified in terms of coating thickness (dry film thickness, measured in microns), number of coats, paint system type (epoxy primer, polyurethane topcoat, zinc-rich primer), and surface preparation standard before painting. Sa 2.5 blast cleaning as the surface preparation standard is the minimum for any corrosion-exposed environment. Mechanical grinding (St 3) is significantly less durable.

Ask for the paint system datasheet — not just the specification description, but the actual product datasheet from the coating manufacturer. It will state the expected service life in different corrosivity categories. A coating with a 10-year expected life in a C3 (medium-corrosivity, urban inland) environment may have a 5-year life in a C4 (high-corrosivity, coastal) environment and a 3-year life in a C5 (very high, marine) environment.

For buildings within 1 km of a coastline, or in any tropical zone with year-round humidity above 70%, we would not specify a standard three-coat paint system as the sole corrosion protection on primary structural members. The premium for a zinc-rich primer or partial hot-dip galvanizing on critical connections is small relative to the cost of early remediation.

Question 4: "What is included in the foundation design, and who is responsible for it?"

This question catches one of the most common gaps in prefabricated steel building contracts.

The supplier designs and manufactures the steel superstructure. The foundation — the concrete pad, the anchor bolt setting, the ground bearing capacity assessment — is frequently excluded from the supply scope and left to the buyer or a local contractor. This is a legitimate division of responsibility, but it becomes a problem when the buyer assumes the foundation is included, or when the local contractor receives no design guidance on what the foundation needs to resist.

Column base reactions — the vertical load, horizontal shear, and overturning moment that each column transfers to the foundation — should be provided by the steel structure supplier as a standard design output. These values are needed to size the foundation correctly. If a supplier cannot or will not provide base reactions, the local foundation designer is working without the key input.

Ask explicitly: is foundation design included in scope? If not, will base reaction forces be provided as a design output? Get the answer in writing before signing.

Question 5: "Can you provide references from completed projects in a similar climate or application?"

This is the softest of the five questions, and the most important for assessing execution risk.

A supplier who has delivered 30 portal frame warehouses to inland Chinese cities has relevant manufacturing experience. A supplier who has delivered warehouses to coastal Mozambique, sub-Saharan port zones, or high-altitude Andean industrial sites has relevant field experience. These are not the same thing.

Ask for project references — not testimonials on a website, but specific completed projects with a contact at the client organisation. You are not necessarily going to call every reference. But a supplier who can name specific projects, specific countries, and specific applications — and is willing to provide client contact details — is giving you a meaningfully different signal than a supplier who describes their experience in general terms.

We have delivered steel structures to port-side logistics facilities in East Africa, food processing plants in southern Africa, and workshop buildings in coastal South America. We do not discuss client names publicly, but on request, we provide verifiable project references to serious enquiries.

The five questions above are not a guarantee of quality. A supplier can provide correct documentation and still make production errors; a supplier with limited documentation can still deliver a reliable building. But in our experience, the answers to these five questions are strongly predictive of the overall level of engineering rigour you will encounter through design, manufacturing, and site support.

Before you sign, send these questions to your shortlisted suppliers and compare the responses. The differences will be informative.

For technical enquiries and project-specific consultation, reach out through Hjsd Warehouse or Hongjishunda Steel Structures. Johnny Joe is available on WhatsApp / WeChat at +86 133 6387 9800.

Written by Johnny Joe, Senior Export Engineer, 20+ years in prefabricated steel structures

Image Specs

 Main Scene 

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• Description: A project manager or buyer — seen from behind or at an angle, no face close-up — sitting at a site office table reviewing a set of structural engineering drawings and calculation documents spread across the table. A hard hat and safety vest are visible on the table beside the papers. Outside the site office window, a steel portal frame building under construction is partially visible. Natural afternoon light. Realistic documentary photography style. No logos, no text overlays.
• SEO alt text: Buyer reviewing steel building structural calculations on site — prefabricated steel warehouse procurement checklist

Technical Diagram 

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• Description: Clean infographic-style checklist diagram on a white background. Title at top: "5 Questions Before You Sign". Five numbered rows, each with a checkbox icon on the left and a short question label:
• 1. Structural calculations — licensed engineer?
• 2. Steel grade + mill certificates? 
• 3. Corrosion protection system + DFT? 
• 4. Foundation scope + base reactions?
• 5. Project references — similar climate? Each row alternates between a light grey and white background band. Clean sans-serif font, professional business style, 1000×1000 px square format. No logos, no decorative imagery.