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Conformity Assessment of the Execution of Steel and Aluminium Structures (CAESAS)

All UK manufacturers of structural products require a UK Conformity Assessed (UKCA) mark. Successfully undergoing conformity assessment of Factory Production Control (FPC) by TWI Certification Ltd (TWI CL) will enable UK manufacturers to affix a UKCA or CE (UKNI) mark and place products on the UK market.

Recognised Third Party Certification from TWI CL is a clear, high profile and independent verification of compliance with BS EN 1090 and UKAS requirements. It provides independent confirmation of competence of welding and fabrication capabilities and personnel, in a clearly defined scope of activity. Furthermore, it increases national and international business potential through demonstrated compliance with legal manufacturing requirements. This is supported by TWI CL being the only Certification Body in the UK able to provide the internationally recognised EWF and IIW Manufacturer Certification Scheme certificates.

TWI CL performs its assessment and certification of manufacturers through its CAESAS scheme and in accordance with BS EN 1090 - the harmonised supporting standard that sets the requirements for conformity assessment of steel and aluminium structures. Furthermore, EN 1090 Part 2 for Steel and Part 3 for Aluminium under the welding section requires compliance to ISO 3834 - Quality requirements for fusion welding of metallic materials. TWI CL provides assessment and certification for both CAESAS/EN 1090 and WFCS/ISO 3834 to ensure our customers have confidence they comply with both standards.

TWI CL is a UK Approved Body and operates under the UK Statutory Instrument (SI) No. 1359 and is an Approved Body for the SI (AB 2400). This enables certified companies to place a UKCA mark on their product or group of products, required for goods being placed on the market in Great Britain, which replaces the previously required CE marking.

For customers who wish to export into Europe and require EU FPC certification to CE mark their products, TWI CL has collaborated with European partners to continue offering this service. More details can be found via the link below.


CAESAS/1: 8th Edition, January 2023

How to Apply

To apply to be assessed against the requirements of EN 1090-1, please complete the application form located in the below link and email to

You will then be provided with a no obligations quotation for conducting the assessment.

Further information on the scheme and how the assessment is conducted can be found in the CAESAS Scheme Description document. 

CCCM-F01 Preliminary Information Enquiry Application Rev 6 May 2023 - 834kb

EU FPC for CE Marking

For manufacturers wishing to export their structural products to the European market and affix a CE Mark, information on how TWI CL can provide this service can be found via the below.

CE Marking

Register of Certified Companies

All companies who have been certified by TWI CL are listed in our register of certified companies.

Register of Certified Companies


Check our list of frequently asked questions about the scheme and the certification process.

View FAQs

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