Guide
External wall insulation and fire safety
On houses, EWI systems with EPS or other combustible boards are widely used within tested systems. On taller buildings, the rules tighten: England bans combustible materials in the external walls of relevant buildings 18 metres and over, and guidance covers residential buildings with a storey at 11 metres or more. Scotland restricts combustible cladding above 11 metres. Mineral wool systems are used where these apply.
Combustible and non-combustible boards
EPS, phenolic and wood fibre are combustible materials used within render systems tested as a whole. Mineral wool is non-combustible. A system's overall classification depends on all of its components, so it's confirmed from the manufacturer's documentation.
Height thresholds
In England, regulation 7(2) bans combustible materials in the external walls of relevant buildings 18 metres and over, and Approved Document B guidance covers residential buildings with a storey at 11 metres or more. Wales has its own amended rules, updated in 2025. Scotland restricts combustible cladding on buildings with a storey more than 11 metres above ground. Northern Ireland follows Technical Booklet E.
Cavity barriers and fire-stopping
On flats and multi-storey buildings, fire breaks and cavity barriers at compartment floors and walls, and fire-stopping around openings, are part of the specification.
Rules under review
The government consulted in 2026 on updates to Approved Document B, including external wall systems and the scope of the combustible materials ban. We follow the guidance in force when your work is specified.
Questions
Is EPS EWI safe on my house?
On low-rise houses it's widely used within tested systems; on taller buildings, non-combustible systems are used.
What is an EWS1 form?
A form used by some lenders to record a fire assessment of external walls on certain residential buildings.
Do bungalows need mineral wool?
Not for fire reasons, generally.