Separating Walls on Boundaries – a gap with fire safety implications
Thursday, 30 March 2017
The VBA Pro-Active Inspection Program has identified many garage brick walls on boundaries being bricked only as high as the course below the lower end of the pitched gutters, and in some cases only as high as the top plate.
This practice saves a number of courses of brickwork and avoids the task of splitting bricks. The gap that extends up to the underside of the gutter is being clad with a metal sheet Colorbond flashing, with the structural framework immediately behind, including wall and roof framing members.
The VBA reminds practitioners that Colorbond flashing is not a fire-rated material and does not provide fire separation in its own right.
What should be done?
The Building Code of Australia – NCC Series, Vol. 2, sets out the Performance Requirements relating to protection from the spread of fire. Key information on this issue can be found in Part 2.3.1 – Fire Safety: Protection from the spread of fire and Part 3.7.1 – Fire Separation, including Part 188.8.131.52 External walls of Class 1 buildings and Clause 184.108.40.206 Separating walls.
BCA Deemed-to-Satisfy (DTS) provisions for External Walls on Boundaries includes four diagrams indicating acceptable construction methods (Figure 220.127.116.11). It is important to note that figure 18.104.22.168 (c) does not permit a gap to be provided between the underside of the gutter, the flashing or brickwork.
Figures 22.214.171.124 provide acceptable construction practices for separating walls between dwellings.
Performance Solutions may be proposed that meet Performance Requirement P2.3.1. However these must be designed by a suitably qualified person and be reviewed and approved by the Relevant Building Surveyor (RBS) to verify compliance with BCA Clause 1.0.5 (Clause A0.5 of Volume 1). This is to occur prior to construction.
For Class 2 to 9 buildings (BCA Volume 1), the Performance Requirements are contained in Clauses CP2 & CP8. Compliance with BCA Volume 1, Clause A0.5 is to be verified by the RBS prior to construction. DTS Clause C2.7 specifies that a fire wall is to be carried through to the underside of the roof covering. Concessions exist to permit certain elements to cross or pass through a fire wall.
What can you, as a practitioner do?
Building practitioners should speak with the RBS prior to carrying out any building work that falls outside the BCA DTS Provisions and Australian Standards.
Building Inspectors are advised to report to the RBS any Performance Solutions used in construction that are not part of the approved documentation, or do not comply with the BCA DTS Provisions and Australian Standards.
Remember: it is not the role of the building inspector during the inspection process to approve Performance Solutions that have not been considered and approved by the RBS.
Examples of non-compliant building work:
|Example of a typical domestic garage wall on the title boundary with a non-compliant fire-resisting wall. Excessive metal flashing between the top of the brick wall and the underside of the gutter can be seen.|
|Example of a typical domestic wall on the title boundary with the timber framing behind the gutter and metal flashing; without the required fire-resisting protection in place. (Note: approximately 3 brick courses are missing and the metal flashing should also continue and be located directly under the roof covering – refer Figure 126.96.36.199(c) of the BCA).|
|Example of a completed domestic project where the top 340mm of the external wall on the boundary is non-complaint.|