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Compartmentation Guide
Open-State vs Closed-State Cavity Barriers
Open-state and closed-state cavity barriers are designed for different construction conditions. Closed-state barriers occupy the cavity continuously, while open-state systems retain a ventilation gap in normal conditions and react to fire to close the cavity.
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Use This Guide
Understand the principle first
Use this guide as a practical introduction, then check the relevant tested system and manufacturer documentation before selecting or installing a product.
Cavity Barrier Comparison
Quick Guide
Open-state and closed-state cavity barriers are designed for different construction conditions. Closed-state barriers occupy the cavity continuously, while open-state systems retain a ventilation gap in normal conditions and react to fire to close the cavity.
Key Points
What You Need to Know
Closed-State
Closes the cavity during normal conditions.
Open-State
Retains a ventilation gap before activation.
Façade Design
Ventilation and drainage requirements affect selection.
Tested Gap
The permitted open gap is product- and system-specific.
Key Principle
What Is a Closed-State Cavity Barrier?
A closed-state barrier fills or closes the relevant cavity location during normal building use. It can be formed from suitable fire-resistant materials or proprietary products depending on the construction.
Because the cavity is closed, the detail must also be compatible with moisture, ventilation and façade design requirements.
Practical Guidance
What Is an Open-State Cavity Barrier?
An open-state barrier is designed to leave a defined gap for ventilation and drainage during normal conditions. Intumescent material reacts to heat and expands to close the gap during a fire.
These systems are often used in ventilated rainscreen façades where a permanent obstruction would interfere with cavity ventilation.
Selection & Application
Which Type Should Be Used?
The correct type depends on the building design, cavity function, façade construction and fire strategy. A ventilated cavity does not automatically mean any open-state product is suitable.
Check the permitted cavity width, orientation, substrate and tested support detail.
Important Detail
Installation Details Matter
The distance to the opposing surface, fixing arrangement and continuity of the barrier can affect performance.
The installed gap should match the tested system, and installers should follow the manufacturer detail rather than using a generic site rule.
Relevant Products
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Use the guide to understand the application, then browse the relevant Fire Protection Direct product categories.
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Frequently Asked Questions
Frequently Asked Questions
It is a cavity barrier system designed to maintain a ventilation gap in normal conditions and close the gap when exposed to fire conditions.
A closed-state barrier continuously closes the relevant part of the cavity rather than relying on an open ventilation gap.
They are strongly associated with ventilated façade systems, but suitability always depends on the actual tested application and construction.
The installed gap should remain within the parameters covered by the system evidence and manufacturer instructions.
Neither is universally better. The correct solution depends on the cavity function, construction and fire strategy.
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