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CROSS Safety Report

Corrosion of fixings securing fire resisting plasterboard

Report ID: 375 Published: 1 July 2014 Region: CROSS-UK

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Overview

A reporter sent pictures from a site where metal plasterboard fixings had deteriorated not long after installation. 

They are concerned that poor quality fixings that are susceptible to corrosion are being used on sites.

Key Learning Outcomes

For construction professionals and designers:

  • Fire resisting partitions should be installed in accordance with the manufacturers specification to ensure the integrity of the fire-resistant boarding is not compromised 

  • Selecting the correct fixings and corrosion protection for the given environment is important to ensure they perform as expected

  • Consider carrying out a condensation risk analysis to determine the dew point to prevent the build-up of moisture and corrosion issues

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A reporter sent pictures from a site where metal plasterboard fixings had deteriorated only a few months after installation (Figure 1). The heads of the fixings were removed using a hole saw to reveal the extent of the corrosion. The reporter says that metal anchors are used to meet fire regulations, although he is uncertain of the origin of this requirement.

Image
Figure 1: corroded metal fixings

Using metal fixings in insulated panels generates cold bridges and can at best cause damp spotting on the surface of the wall.  At worst it can lead to corrosion if a low-grade metal fixing is used. They are concerned that cheap metal fixings are being brought into this country from the Far East and the market is flooded with them. 

Using metal fixings in insulated panels generates cold bridges and can at best cause damp spotting on the surface of the wall. At worst it can lead to corrosion if a low-grade metal fixing is used.

Many of these, they believe, are susceptible to corrosion. When asked to provide metal anchors to comply with board manufacturers’ requirements the reporter’s firm offers a stainless steel version but even this causes cold bridging.

Expert Panel Comments

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This is a good example of the role that understanding materials plays in assuring safety. Corrosion and degradation always affect safety to some extent and only feedback of performance in practice will assure on going reliability. 

Avoiding interstitial condensation

In any wall construction it should always be assessed where the dew point may lie so as to avoid interstitial condensation. Cold bridges can locally change the dew point, and potentially cause corrosion to unsuitable components. It may be that the effects of cold bridging were not taken account of in this case. 

In any wall construction it should always be assessed where the dew point may lie so as to avoid interstitial condensation. Cold bridges can locally change the dew point, and potentially cause corrosion to unsuitable components

It is understood from industry sources that two metal fixings are usually required per board to satisfy the need for a fire rating. However, the source of this information is not known. The issue of how to avoid cold bridging while satisfying a fire rating is also unclear. If any readers can shed light on the situation, please advise CROSS by emailing us at  team.uk@cross-safety.org. The experience also links back to previous CROSS reports of poor quality materials. 

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