Rainscreen cladding systems rely on a ventilated cavity behind the outer panels to manage moisture. That same cavity can allow fire and smoke to spread rapidly if it isn't correctly fire-stopped — which is where cavity barriers come in.
What a cavity barrier does
A cavity barrier closes the ventilated gap at key points — around openings, at floor/compartment lines, and at the top and bottom of the wall — so a fire in the cavity can't travel unchecked between floors or compartments.
Where they're required
Cavity barriers are required in ventilated rainscreen systems generally, with specific positions and fire ratings set out in Approved Document B and the system manufacturer's tested specification. Getting the positions wrong is one of the most common defects found in post-Grenfell external wall reviews.
Installation matters as much as design
A correctly specified cavity barrier that's poorly installed — gaps, compression, wrong fixing centres — doesn't perform as tested. We install to the exact tested detail and photograph cavity barrier positions before the outer panels go on, as part of our handover records.