Cavity Barriers

We supply both closed state and open state cavity barriers to meet the needs of modern construction.

Closed State Cavity Barriers are permanently closed and used in traditional applications like party walls, floor zones, roof spaces, and masonry/timber frame construction. They are designed to block fire and smoke movement through voids at all times.

Open State Cavity Barriers (OSCBs) are specially engineered for ventilated façades and rainscreen cladding systems. They allow air and moisture to pass through during normal operation but expand and seal the cavity in the event of a fire.

Masonry Cavity Walls

In traditional masonry construction, cavity barriers are installed within the wall cavity to prevent fire and smoke from traveling through the void between the outer and inner leaves of brick or blockwork. These closed state cavity barriers are typically placed at junctions with separating walls and floors, around openings such as windows and doors, and at compartment lines to preserve the fire integrity of the structure.

Timber Frame Construction

Timber frame buildings often have large, continuous cavities that can act as hidden channels for fire and smoke spread. To address this, closed state cavity barriers are strategically placed at compartment lines, floor zones, and roof junctions. Special attention is given to ensuring the barriers maintain integrity despite timber shrinkage or movement, and that they’re compatible with breathable membranes used in timber construction.

Roof Voids and Eaves

Roof voids, eaves, and loft spaces can be vulnerable to fire spread, especially where compartments meet the roofline. Cavity barriers in these areas are used to seal off hidden paths for flame and smoke, often at wall plate level, between rafters, and across roof slopes in multi-unit buildings. They are especially important in terrace or apartment buildings where fire could move between dwellings via shared roof space.

Party Walls and Floors

At the junctions of party (separating) walls and floors between dwellings or commercial units, cavity barriers prevent lateral fire and smoke spread through hidden voids. These are crucial for maintaining compartmentation in compliance with building regulations. Barriers here must offer both fire resistance and, where applicable, acoustic insulation to meet dual performance requirements.

Ventilated Cladding Systems (Rainscreen Façades)

These systems create a ventilated cavity behind the outer cladding, which improves thermal performance and moisture control but also introduces a risk of chimney-effect fire spread. Open state cavity barriers (OSCBs) are installed horizontally and vertically within the cavity. Under normal conditions, they allow air flow and moisture drainage. In a fire, their intumescent materials expand to seal the cavity, preventing flame and smoke from racing up or across the façade.