Engineers Australia proposes key NCC changes to combat building defects

Engineers Australia is advocating for significant changes to the National Construction Code (NCC) aimed at preventing water leaks, the predominant cause of defects in Australian apartments and commercial buildings.

Water leaks account for a staggering 80-90% of building defects, costing owners and insurance companies up to $3 billion annually.


The Watershedding Community of Practice, in collaboration with the Australian Building Codes Board, has proposed four critical changes to the NCC:

Using Gravity: New requirements will focus on the natural collection, redirection, and drainage of water, utilizing principles that date back to Roman engineering over 2,000 years ago.

Fixing Flat Areas: To eliminate leaks, the changes propose removing flat surfaces from balconies, roofs, and basement floors—areas particularly prone to water issues.

Managing Underground Water: For the first time, the NCC will address underground water management. New guidelines for outdoor concrete slabs will include casting a slope (1:80) to drainage outlets, a 70mm step down at sliding doors, a 70mm edge around the perimeter, and 50mm edges at construction joints during the building process.

Concrete as Key: Concrete slabs are essential for waterproofing. Structural engineers will need to consider how slabs will sag over a decade to ensure the structure continues to drain effectively.

Michael van Koeverden, a member of the Watershedding Community of Practice, emphasized the urgency of these changes, stating, “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. When membranes fail, the structure must continue to drain water.”

Engineers Australia CEO Romilly Madew AO echoed this sentiment, highlighting the necessity of addressing these challenges to meet Australia’s unprecedented housing demand. “Engineers are critical to delivering resilient and safe buildings. We fully support the government’s efforts to implement comprehensive building reforms. Improving standards is a responsibility that spans the entire industry, including builders, architects, developers, and designers,” Madew stated.

The proposed changes to the NCC 2025 aim to improve design and construction processes, enhance collaboration among all parties involved in building projects, and ultimately deliver safer, more resilient buildings for Australians.

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