Cross UK Report 1017: brick slips falling from height

Collaborative reporting for safer structures. Report 1017: brick slips falling from height

A reporter has been examining failures in brick slip systems and has found the same issues in three different projects. The projects are all in the UK but are unrelated, and were completed around the mid-2010s. It has been found that the adhesive holding the brick slips to backing boards is failing and the slips are falling to the ground.

A brick slip falling from any height could cause injuries and possibly a fatality. In the cases studied, the buildings are all over three storeys and adjacent to busy streets.

In one of the buildings, a number of brick slips at a considerable height above ground had de-bonded from the composite board substrate and were lying on an adjacent roof. It was clear that the adhesive bond between the composite board and slips had failed. Possible causes are:

  • the adhesive layer was applied too thinly or inconsistently; or

  • the adhesive used may be inappropriate for the job.

On another building, with several areas of failure apparent, inspection identified that, in almost all cases, the bond between the brick slip and adhesive had failed. A contributory cause may be that the composite backing boards are bowing.

This and other investigative work by the reporter’s firm has identified failure modes in adhesively bonded brick-slip systems due to deterioration of the adhesive and/or its interfaces. For example, many adhesives, including epoxies, are known to lose their ductility over time. This means that they become brittle with age and have less capacity to accommodate any movement of the system’s components.

Brick slips are porous, allowing moisture and air into the interface between the adhesive and the slip. Hydrolysis and oxidation are just two of the mechanisms that can deteriorate adhesive bonds over time. In such cases, it is important to determine whether the adhesive has been correctly specified as being adequate for its intended purpose in order to comply with building regulations.

An additional complication is the UK government’s ban on combustible products for new work on residential buildings over 18m in height, as adhesives are generally combustible. This means that any remedial works will need to comply with this directive.

It is the reporter’s view that, if they are aware of several failures, there must be many more actual or potential future failures throughout the country. Steps need to be taken to identify buildings where adhesively fixed brick slips are incorporated and carry out structural inspections.

In the cases considered here, one building has been reclad with a mechanically fixed system and the other two have temporary protection around the failed areas pending further investigation.

Comments

This report is of concern because there must be very many buildings with brickwork cladding that incorporate brick slips, some attached by mechanical means and some with adhesives. The practice goes back many years, and a variety of systems have been used. Some will have been more robust and successful than others, and some of the suppliers no longer exist, so records are sparse or non-existent.

It is known that in the past there might not have been enough testing of brick slip systems, but developments in recent years have improved their general quality.

Components and materials do fall off buildings, and there are fatalities and injuries. In 2007-8 the Scottish government commissioned CROSS to investigate falls of material, and 1,200 cases were recorded – mostly from older buildings, with 40% associated with masonry. There were several reports of injuries due to pedestrians being struck. In addition, CROSS has had many reports about falling objects.

CROSS has also published reports and alerts on problems with resin adhesives in relation to tension systems: see Tension systems and post-drilled resin fixings, bit.ly/TensionSystems. Although these are not the same as brick slip failures, the report points to some long-term consequences from the inappropriate use of some adhesives. Specifiers and designers should assure themselves of the appropriate longevity of products.

The reporter makes a good point that if they know of a number of incidents then others must know of far more. Additional information is needed in order to assess the level of potential risk, so reports are requested from anyone who has experience of brick slips falling or becoming loose. A useful reference on the subject is Alexis Harrison’s article ‘Are brick slip cladding systems safe?’ (see bit.ly/HarrisonBrickSlips) 


Key learning outcomes

For designers:

  • consider the likely lifespan of the materials and components used on façades
  • some adhesives used may not adequately give the required robustness and longevity.

For the construction team:

  • manufacturers’ instructions for the selection and application of adhesives must
    be followed
  • ensure that adhesives are correctly applied
  • do not substitute products without the approval of the designer.

For building owners:

  • CROSS is very keen to hear about other cases of brick slip failures.

Image credit | Alamy

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