External Wall Insulation (EWI): Advice for Building Owners

External Wall Insulation (EWI): Advice for Building Owners2021-02-12T15:07:46+00:00

External wall insulation (EWI) cladding systems with medium to heavy-weight cement render or ceramic brick-slip finishes have been installed on domestic two-storey dwellings and on low, medium and high-rise multi-storey housing blocks throughout the UK and may pose serious risk of injury or to life not only of the building occupants but also to pedestrians and the general public from potential collapse of parts of external wall insulation systems falling from buildings:

  • due to potential inadequacies of the structural design calculation methodologies of the external wall insulation (EWI) systems and/or

  • due to poor installation and/or

  • due to deterioration from rainwater ingress into the external wall insulation (EWI) systems and premature breakdown of the finishes

           Fig1. EWI Cladding Collapse – High-Rise

Fig2. EWI Cladding Collapse – Low-Rise

Fortunately, external wall insulation (EWI) cladding system collapse is not a common occurrence but all those responsible for the maintenance of a building with external wall insulation (EWI) systems with either a cement render or brick-slip finish should make themselves familiar with the advice contained in the Department for Communities and Local Government ADVICE NOTE 13, Ref DCLG/BSP/Advice Note/13/111217, 11th December 2017 and take appropriate action to ensure the safety of their building.


“Where inadequate design and/or installation reduces safety factors, EWI systems are more vulnerable to:

  • damage from high wind speeds;
  • other installation defects such as poor water-tightness (which can lead to insulation becoming water-logged and heavier as a result);
  • and variations in the design and installation quality of mechanical or adhesive fixings.

These potential defects increase the risk of the EWI system becoming detached from the building and falling from height. This in turn poses risks to life safety. With render or brick-slip EWI systems there is a heightened risk of the render or brick-slip layer detaching from the insulation underneath where these defects are present.”

“If not undertaken recently, building owners should consider an immediate audit or review of the buildings for which they are responsible ……”

Fig3. EWI Render Failure – Domestic Housing

I-CAN (Insulation Consultancy and Analysis) Chartered Building Engineer staff has been involved in investigating high profile external wall insulation failures for over 30 years including complete EWI system detachment from high rise multi-storey tower blocks.

If you require assistance in carrying out investigations of existing external wall insulation systems failures please click here to contact us.

Related articles:

Department for Communities and Local Government ADVICE NOTE 13, Ref DCLG/BSP/Advice Note/13/111217, 11th December 2017 – https://assets.grenfelltowerinquiry.org.uk

Advice note for external wall systems that do not incorporate Aluminium Composite Material (ACM) – https://assets.grenfelltowerinquiry.org.uk

Fire performance of external thermal insulation for walls of multi-storey buildings, third edition (BR135) – https://assets.grenfelltowerinquiry.org.uk/