Engineers Australia has called for changes to the National Construction Code (NCC) that could prevent the leading cause of defects in Australian apartments and commercial buildings.

The leading cause, water leaks, account for 80-90% of defects and cost building owners and insurance companies up to three billion dollars annually.

“Urgent change is required to address building performance and leakage issues. Structural engineers play a critical role in preventing building leaks. While membranes typically last 10-15 years, structural designs are intended to last 40-60 years,” Engineers Australia and Watershedding Community of Practice member Michael van Koeverden says.

“The proposed changes to the NCC 2025 aim to address these issues by improving design and construction processes and enhancing collaboration among all parties involved in building projects.”

Industry experts from the Watershedding Community of Practice have collaborated with the Australian Building Codes Board to propose four critical changes to the code:

1. Using gravity: New requirements focus on naturally collecting, redirecting and draining water, just like the Romans did 2000-plus years ago.
2. Fixing flat areas: Removing leaks by removing flat surfaces from balconies, roofs and basement floors, which are common trouble spots for water issues.
3. Managing underground water: Addressing underground water, new guidelines for outdoor concrete slabs include casting the following into the structure while being built and not after:
   • A slope of (1:80) falls to drainage outlets.
   • A 70mm step down at sliding doors.
   • A 70mm edge (hob) around the perimeter.
   • 50mm edges (hobs) at construction joints.
4. Concrete is key: Concrete slabs are vital for waterproofing. Structural engineers must now consider how slabs will sag over ten years when designing them so the structure will continue to drain.

Engineers Australia encourages public feedback on the NCC 2025 improvements related to waterproofing and water shedding. The proposed changes are open for review on the Australian Building Codes Board website.