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CROSS Safety Report

Brick slips falling from height

Report ID: 1017 Published: 13 August 2021 Region: CROSS-UK


Overview

A reporter describes cases of brick slips falling from height due to adhesive failures and considers that there is a danger to the public.

Key Learning Outcomes

For building owners:

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

For designers:

  • Consider the likely life-span of the materials and components used on facades
  • Some adhesives used may not adequately give the required robustness and longevity

For the construction team:

  • Manufacturer’s 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

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A reporter has been examining failures in brick slip systems and has found the same issues in several projects. They are all in the UK but 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 slips are falling to the ground.

A brick slip falling from any height could cause injuries and possibly a fatality. In the cases in point, the buildings are over 3 storeys and all are 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: 

  • Adhesive layer is applied too thinly or inconsistently
  • Adhesive may be inappropriate for the job

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

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

Failure modes in adhesively bonded brick slip systems

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, meaning that they become brittle with age and have less capacity to accommodate movement of the system components.

Brick slips are porous, allowing moisture and air to 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 the Building Regulations.

Impact of ban on combustible products

An additional complication is the UK Government 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.

It is the reporter’s view that if they are aware of several failures there must be many more actual or potential future failures out there, and 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 has been reclad with a mechanically fixed system and the other two have temporary protection around the failed areas pending further investigation.

Expert Panel Comments

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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 were 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.

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

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 had had many reports about falling objects.

CROSS publication on resin adhesives

CROSS has also published reports and Alerts on problems with resin adhesives in relation to tension systems: Tension systems and post-drilled resin fixings which, although not the same as brick slip failures, 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.

Call to share information about brick slip issues

The reporter makes a good point in 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.

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?.

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