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CROSS Safety Report

Major UK steel manufacturer talks about steel substitution

Report ID: 761 Published: 1 January 2019 Region: CROSS-UK

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Overview

A correspondent is concerned that cold formed S235 steel is being used in place of hot formed S355 steel, as this can have dangerous implications.

Key Learning Outcomes

For construction professionals:

  • Substitution of construction elements, for a lower grade material, should not be made without design team verification

  • Talk to the design team and regularly discuss your use of products, components, and materials

  • Consider introducing a quality assurance process that covers the correct use of products, components, and materials on site

For civil and structural design engineers:

  • Share your knowledge of the behaviour of products, components, and materials

  • Routinely raise the risks associated with substitutions to contractors and the wider project team

  • If you are concerned that the correct material grade may not have been installed on site, consider asking the contractor for the material certificates

Full Report

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A correspondent has written in response to the issues that have arisen from report 740 which discussed the issue of using S235 cold rolled steel instead of S355 hot rolled steel. As a UK manufacturer of both hot and cold structural hollow sections, they are concerned that cold formed S235 steel is being used in place of hot formed S355 steel, as this can have dangerous implications.

Hot v. cold formed hollow sections

In their view, there is good availability of both cold and hot formed steel in the UK and they feel that a few may be letting the industry down. They refer to the Hot v. cold formed hollow sections article published in The Structural Engineer in 2007 on the comparison and effects of hot and cold structural hollow sections and ask if this article should be re-issued with the addition of CE marking to help the industry?

The correspondent notes that S235 is generally manufactured for the commodity industry. This does not require the same quality, traceability and testing as S355 so will have a price difference. The two product standards, EN10219 Cold formed Structural Hollow Sections and EN10210 Hot finished Structural Hollow Sections, are different.

Concerns of using cold formed S235 instead of hot formed S355 steel

The correspondent has come across the substitution of S235 for S355 but is very alarmed that this is happening with cold S235 for hot finished S355. Material manufactured to EN10219 and EN10210 will be CE marked, and there should be a clear identification with the certificate and label that goes with the steel.

Material manufactured to EN10219 and EN10210 will be CE marked, and there should be a clear identification with the certificate and label that goes with the steel

The correspondent goes to say that if there are any issues arising from the misuse or mis selling, then the responsibility lies with the person/company placing the product in the marketplace.

The main problem, they believe, is that the tested values of the cold EN10219 will be much higher than the minimum yield certified due to the manufacturing process but will lose yield when heat is applied. The people responsible for upgrading are playing a dangerous game.

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

A key safety message that CROSS comments keep repeating is that there should be verification that what is built matches design intent.

The importance of quality assurance and control

There can be no more serious deficiency than having a material that doesn’t have the strength the designer thought it had. A rather obvious issue is that you cannot tell the difference in strength between two pieces of steel (or concrete) just by looking at the product. Therefore, quality assurance (QA) on product procurement (and quality control (QC)) are essential components in assuring design safety.

A rather obvious issue is that you cannot tell the difference in strength between two pieces of steel (or concrete) just by looking at the product. Therefore, quality assurance (QA) on product procurement (and quality control (QC)) are essential components in assuring design safety

Is the substitution of materials an industry wide issue?

There are issues around the whole construction industry regarding substitution of materials (usually for something cheaper), and the clear marking of products and the availability and ability of someone to check. If components and materials are marked clearly (and accurately), and there is rigorous checking on site then these things can be avoided.

The matter of false certificates has previously been addressed by the Standing Committee on Structural Safety (SCOSS) in the alert Anomalous documentation for proprietary products - February 2013.

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