Hidden flammable cladding ‘in 2,000 high-rises’

Up to 2,000 properties may have been built using flammable cladding and insulation that cannot easily be identified, a report has warned.

An internal document from one of the country’s biggest cladding firms, seen by Telegraph Money, has warned that high-rise blocks have been built using flammable materials that may not be discovered unless invasive tests are carried out. It warned that poorquality and highly flammable materials were often hidden behind a thin concrete layer, meaning basic building checks may not highlight the problem.

This could have major repercussions for buyers who purchase new-build flats in buildings that have no visible cladding, because problems could be discovered years later that cause their homes to plummet in value. Surveyors who inspect a property will demand that buildings with visible cladding have passed an External Wall Fire Review (EWS1) test before they issue a valuation (see telegraph.co.uk/go/ews1 for more).

Without this approval, the property is considered worthless as banks will not offer mortgages. If the property has no cladding that causes concern the surveyor will issue a valuation and the transaction can proceed as normal. However, the leaked report warns that many buildings have combustible expanded polystyrene (EPS) insulation hidden below a thin layer of concrete.

Materials are rated from A1 to F based on flammability, with EPS described as an “extremely poor, E-class product”.

Rainscreen cladding systems were highlighted as a particular area of concern. No public figures are available on the number of properties with potential problems. However, a letter from Clive Betts MP, chairman of the housing, communities and local government committee, in 2018 cited a separate report by Rockwool, a cladding firm, which warned that at least 90pc of buildings with rainscreen cladding were built using flammable insulation.

The report estimated that about 1,700 blocks had yet to be identified by safety officials, given the number of high-rises built with this cladding. More than 18 months later, fresh information suggests that 80pc-90pc of problem blocks have not been identified. The report said that in many cases freeholders had refused to carry out EWS1 checks because “they fear the cost of remediation”. It also warned that “combustible cladding and insulation are an endemic issue”.