Cladding is a construction technique that refers to the components that are attached to the primary structure of a building to form non-structural external surfaces, including the weather-exposed outer layer or screen, fillers, insulation, membranes, brackets, cavity barriers, fire breaks, flashing, fixings, gaskets, and sealants.

detailed cladding image

A typical cladding detail showing the structural aspect of a wall, the insulation layer then the external weatherproofing and fixings.

What is ACM and non-ACM cladding?


An ACM clad building

An ACM clad building

(Aluminium Composite Material) cladding is aluminium sheets bonded to a central core. It is light and versatile and comes in many decorative finishes.  It provides weather proofing and has good insulative properties.

Category 1 ACM has a non combustible core

Catagory 2 ACM has a polythene core that has been treated with flame retardant chemicals

Catagory 3 ACM has an untreated polythene core.

The untreated polythene core was determined to be a major cause of rapid fire spread at Grenfell Tower.  This was a contributing factor to the tragic loss of life.


These cladding types include other materials such as:

Composite panels

Typically something that looks like wood, also known as HPL (high pressure laminate)

An example of a HPL system

An example of a HPL system

Insulated Render

A cladding render system

A render system

Whilst the render itself in generally non combustible, it is usually applied over Expanded Polystyrene (EPS) Insulation blocks.  If the render is not kept free of cracks / chips the insulation behind can ignite in the event of a fire.  As the insulation burns away, sections of the render fall.  Visit our videos page to see the performance of a render system under test condtions.


(Expanded Polystyrene) used as an insulation material behind a rendered or metal finish.

EPS insulation being installed

EPS insulation being installed


fire test

A still from a fire test video showing EPS Insulation after 2m 14s of exposure to flame.


A Timber Cladding System

A Timber Cladding System

Timber cladding is more popular on low rise buildings, however it is often used on taller buildings to give a different aesthetic to the façade.  It is also often used as partitions between flats and for decorative screening.

What is an EWS1 Form?

EWS stands for External Wall System.

The EWS1 Form was introduced in December 2019 to give lenders more confidence in offering mortgages on apartments built before changes to the building regulations in 2018.  It was developed by lenders and the Royal Institution of Chartered Surveyors (RICS), to make the valuation process easier.

The form is completed by a competent surveyor following an intrusive survey of the external walls.  The building construction documents (O&Ms) can be used in conjunction with a survey report, however an EWS1 Form cannot be completed solely on the contents of O&M documents.

The EWS1 Form can provide confirmation that the material on external walls poses a limited risk of fire or is non-combustible. Alternatively, if materials do pose a fire risk, a Fire Engineer needs to complete section B2 which will detail the necessary remedial works.  A Fire Engineer may also issue instructions for ‘Interim Measures’ such as a waking watch.

Any EWS1 Form needs to be reassessed if any significant changes occur to the external wall or attachments of the building and is valid for up to 5 years from the date at which it is signed.

The EWS1 Form has unfortunately caused severe problems with lenders requiring it on buildings for which its was not designed. It has also held up valuations and financing on many properties.

In January 2021 the RICS announced a consultation to review the EWS1 Form and process with a view to making it much clearer as to which properties require it and hopefully open up the lending market as a result. See our News page for further updates.

Click here to see the EWS1 Form

If you have a cladding issue and need help in progressing matters to conclusion, there is no time to lose.
Call us on 0203 627 0581 or click here to send us a message.