Building Code of Australia (BCA) Clause FP1.4: Weatherproofing Requirements for Louvres

30 JUNE 2025

Authored by Jessica Tayag

Overview of Performance Requirement FP1.4

Performance Requirement FP1.4 of the National Construction Code (NCC) mandates that roofs and external walls—including openings around windows and doors—must prevent water penetration that could result in:

Unhealthy or dangerous conditions, or loss of amenity for occupants; and
Undue dampness or deterioration of building elements.

Importantly, the NCC does not provide Deemed-to-Satisfy (DtS) Provisions for compliance with FP1.4 in relation to external walls. As a result, compliance must be demonstrated through a Performance Solution.

Responsibility for Sign-Off

The development and approval of a Performance Solution under FP1.4 generally involves:

Qualified Façade Consultant: Responsible for designing a solution that ensures the façade system complies with FP1.4 performance criteria.
Principal Certifying Authority (PCA): Responsible for reviewing and approving the proposed Performance Solution to ensure it meets the NCC's performance requirements.

Louvres and Weatherproofing Compliance

Fixed louvres are assessed against AS 4740, which outlines performance requirements for pressure drop and rain resistance. While high-performance louvres can achieve Class A rain resistance, meaning 99–100% effectiveness, it is essential to understand that louvres are not watertight. Some level of water ingress is inevitable due to their open construction. Consequently, fixed louvres are generally not specified for applications that demand total weathertightness.

Addressing FP1.4 with Louvres

To achieve compliance with FP1.4 when using fixed louvres, the following considerations are critical:

Façade Integration: The interface between the louvre and the surrounding façade must be carefully detailed. This includes the design of flashings and sealing systems to prevent water ingress at the perimeter.
Product Selection: Building designers and specifiers must evaluate the rain resistance performance of different louvre types. This includes assessing the percentage of rain deflection and determining an acceptable level of water ingress for each specific application.
Performance Matching: The selected louvre system should balance rain resistance with airflow requirements, aligning with project-specific environmental and operational conditions.

Example: Louvreclad Kensington Series

The Louvreclad Kensington Series® is an example of a high-performance louvre that achieves:

Class A rain resistance (100% effective)
Class 3 aerodynamics

This makes it suitable for projects where maximum rain defence and airflow are critical, though still within the context of acknowledging that full watertightness is not feasible with any fixed louvre system.