Cavity Barriers

Purpose Of Cavity Barriers

They serve to:

1. Contain Fire And Smoke: They restrict the movement of fire and smoke within cavities, thereby preventing the spread to other parts of the building.
2. Compartmentalisation: They help in creating fire compartments within buildings, limiting the area affected by fire and enhancing the overall fire safety strategy.
3. Protection of Structural Elements: By preventing fire spread within cavities, they protect critical structural elements from premature failure.

Types Of Cavity Barriers

1. Intumescent:
   • Mechanism: These barriers expand when exposed to heat, sealing gaps and preventing fire and smoke passage.
   • Applications: Suitable for cavities around windows, doors, and service penetrations.

2. Non-Intumescent:

1. • Materials: Typically made of mineral wool, gypsum, or other fire-resistant materials.
   • Applications: Used in larger cavities and voids where intumescent materials are not necessary.

3. Rigid:

1. • Materials: Made from rigid fire-resistant materials like calcium silicate boards or metal sheets.
   • Applications: Used in specific construction details where a solid barrier is required.

4. Flexible:

1. • Materials: Made from flexible materials like fire-resistant fabric or blankets.
   • Applications: Ideal for irregularly shaped cavities and areas requiring flexible solutions.

Installation Of Cavity Barriers

1. Location:
   • External Walls: Around the perimeter of wall cavities, especially near openings and junctions.
   • Internal Walls and Floors: At intervals within cavities and at junctions with other fire-resistant elements.
   • Roof Spaces: In roof voids and around penetrations.

2. Spacing:

1. • The spacing of cavity barriers is determined by building regulations and the specific fire safety strategy of the building. They must be installed at regular intervals to effectively compartmentalize the cavity.

3. Fixing Methods:

1. • Mechanical Fixings: Screws, bolts, and brackets used to secure rigid barriers.
   • Adhesive Fixings: Fire-resistant adhesives for flexible barriers and some rigid barriers.
   • Compression Fit: For materials like mineral wool, which can be tightly packed into cavities.

4. Coordination with Other Systems:

1. • Cavity barriers must be coordinated with other fire protection systems such as firestopping, fire doors, and dampers to ensure a comprehensive fire protection strategy.

Regulatory Requirements

1. Building Codes and Standards:
   • Compliance with local building codes and standards (e.g., NFPA, IBC, UK Building Regulations) is essential. These regulations specify the requirements for cavity barriers, including their fire-resistance rating, placement, and installation.
   • Specific standards like BS 9991 and BS 9999 in the UK provide detailed guidance on the use of cavity barriers in different building types.

2. Testing and Certification:

1. • Cavity barriers should be tested and certified to relevant fire safety standards (e.g., EN 1366-4, ASTM E814). Certification ensures that the barriers perform as expected under fire conditions.

3. Inspection and Maintenance:

1. • Regular inspections are necessary to ensure that cavity barriers remain effective over time. Maintenance may involve replacing damaged or disturbed barriers and ensuring that any new penetrations are properly sealed.

By properly designing, installing, and maintaining cavity barriers, buildings can significantly improve their resistance to fire spread through concealed spaces, thereby enhancing overall safety and structural integrity.