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CROSS Safety Report

Poorly applied external insulation on buildings

Report ID: 1203 Published: 21 August 2023 Region: CROSS-UK


This report concerns external insulation on buildings being inadequately applied and fixed, with poor control of the workmanship standards, leading to potential safety concerns and damage to the property.

Key Learning Outcomes

For owners, clients and specifiers:

  • Be aware that insulation and renders can fall if not properly designed and installed

  • Consider the advantages of work guarantee schemes that require providers to be competent

For providers and installers of external insulation:

  • External insulation fitted to buildings must be designed by a suitably qualified and experienced person (SQEP)
  • Insulation installers should be appropriately trained and experienced
  • Installations should be monitored by competent supervisors
  • The Construction Fixings Association provides guidance for those specifying, using and testing fixings

Full Report

Find out more about the Full Report

The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


This report concerns external insulation on buildings which has been poorly applied and fixed. The reporter says workmanship issues observed include insulation applied in a haphazard method, multiple unnecessary holes drilled, insulation cut into shape on the installer's knee, and insulation panels having to be reattached several times because of defects in fixing. Generally, the reporter is concerned about poor standards of workmanship which can have safety implications and result in poor insulation for the buildings concerned.

The reporter considers there may be poor training, a lack of appreciation of the risks of material failure, and a lack of checking of the standard of work. The reporter wants to see higher standards of installation and inspection, to avoid future failures and falls of material.

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

External insulation work is becoming more prominent as energy saving and other initiatives to improve housing stock come to fruition. The reporter is therefore right to be concerned about the fall of material from buildings.  There is a need to consider the life-safety risk that could occur during the potential life of the building and its cladding, the potential life being likely to extend beyond any theoretical design life of the building.

Where a system can fail with no visible prior warning, such as is possible in the case of externally fixed insulation and renders, the need to consider risks is amplified. The risk, for example, of insulation material becoming waterlogged and detaching because of its increased weight, potentially with other cladding materials from height, is a key concern and should be addressed within the design. CROSS has published a number of reports concerning falls from buildings including, in 2022, report 1081 - Another example of brick slips falling from height


The risk, for example, of insulation material becoming waterlogged and detaching... is a key concern and should be addressed within the design

Any insulation scheme must be designed by a suitably qualified and experienced person (SQEP). Poorly designed insulation could not only be hazardous due to falling materials but also cause extensive damage to a building including problems associated with condensation within the wall structure.

Works could be undertaken by a range of providers; however, regardless of which organisation undertakes the work, competent installers are required. If the insulation is not fitted properly, there is a high risk of moisture being trapped within the construction causing significant damage and the potential for the insulation and the external render to come away from the building in storm and other weather conditions.

There are many aspects of the work that need very careful consideration both during design and installation, for example:

  • impacts upon the wall of internal and external moisture
  • weather dependency of work to avoid trapping moisture
  • detailing to allow for future maintenance including window replacement
  • treatment around air bricks and other vents
  • not bridging damp proof courses
  • avoiding water traps at eaves and generally ensuring compatibility with roof edges
  • maintaining access to cables, pipes and other external fittings
  • security and life of fixings in different wall materials

Clearly, planning for and undertaking the work requires knowledge, skills and experience. Competent providers will ensure their operatives are appropriately trained to use the various materials, and that the work is monitored by competent supervisors. Some material manufacturers will provide training on the use of their materials. Insulation work guarantee schemes, such as offered by the Solid Wall Insulation Guarantee Agency, may require that installers are appropriately trained and supervised.

Competent providers will ensure their operatives are appropriately trained to use the various materials

CROSS has been concerned for some time about the use of structural fixings where these, so called minor, items have not received the attention they deserve given their safety critical nature. CROSS published its Safety Alert, The selection and installation of construction fixings, in 2010. The specification of suitable fixings is a critical part of the design of externally fixed insulation. The designer must take into account all wall materials being fixed to, including existing renders, masonry units and mortar joints, all of which may significantly affect the type, spacing and capacity of fixings. The exposure and durability of fixings must also be considered. The Construction Fixings Association provides guidance, training and other support to those specifying, using and testing fixings.

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