Quick Search

669 Light Gauge Steel Framing and responsibilities on site

Report ID: 669

Published: Newsletter No 51 - July 2018

Report Overview

As an increasingly popular method of supporting building envelopes, Light Gauge Steel Framing (LGSF) was utilised on the residential project in question.

Report Content

As an increasingly popular method of supporting building envelopes, Light Gauge Steel Framing (LGSF) was utilised on the residential project in question. The LGSF acted as a secondary structure to the main concrete frame to carry finishes, façade and glazing at structural openings. The frame was installed satisfactorily by a sub-contractor and handed over following completion.

After the installation, additional balcony elements were fitted to the primary frame located at the first and second storey. Balcony brackets were required at a number of opening jambs, but no prior arrangements were made within the concrete frame to connect the balcony, nor was it coordinated with the LGSF sub-contractor or designer. In order to connect balcony brackets to the primary frame, the LGSF jambs were trimmed short at both head and base connections.

The glazing to the structural openings had already been installed and due to the removal of the LGSF jamb connections, it was now the plasterboard which both suspended the LGSF locally and restrained the glazing against wind and other loading applied. Fortunately, the LGSF sub-contractor was made aware of the occurrence, raised the issue with the supplier, and a remedial design was produced to bridge the brackets and reconnect the LGSF jambs back to the primary frame.

If left unnoticed, this structural fault could easily have been covered and neglected, where under much lower loading than designed for, may have resulted in failure of the envelope and glazed openings. This could have led to the LGSF, glazing or other finishes failing and falling from their installed position.

It is important to remember that LGSF is a structural steel system and it is of vital importance that notching and material removal not confirmed within the design does not take place. Examples such as the above, where future elements of the site program require space not previously provided, must be coordinated during the LGSF design and ahead of installation to mitigate scenarios like this.

Comments

The LGSF sub-contractor is to be congratulated on their diligence in spotting the conflict which could have had serious consequences. It begs the question however as to what happened to the site supervision?

There are two main issues. The first is that there was a failure to recognise at the design stage that provision would be needed to accommodate the balconies. CDM 2015 promotes closer working between designers, facilitated through the Principal Designer, and the transfer of relevant information in order to overcome interface issues.

The second is the failure of the Principal Contractor to refer the issue back to the relevant designer once the problem became known and before allowing notches to be made. The report highlights the problems of multiple sub-contractor suppliers without one overall guiding hand. In any structure, the Principal Designer ought to ensure there is a viable load path which all parties understand and respect across all structural parts - whoever supplies them.

There is always a need to inform following trades (and indeed future occupiers through CDM) of the structural importance of secondary elements. This case illustrates once again some of the flaws highlighted in the Independent Review of Building Regulations and Fire Safety: final report.

Balconies, particularly cantilever balconies, must always be treated with care. There are frequent failures and there have been many fatalities due to collapsing balconies. Entering “balcony” in the Quick Search facility on the Structural-Safety website will give examples.

 

CROSS depends on you for reports - if you have experienced a safety issue that you can share with CROSS, please Submit a CROSS Report

If you have any comments regarding this CROSS report, please Submit Feedback

View other CROSS reports published in Newsletter No. 51

Images

LGSF trimmed to allow for balcony brackets



Register

How to Report

Online submission:
Submit by post: