Mezzanine Addition

Access, Egress and Use

NCC 2022 Volume 1

Area of NCC Requirements:

• Section D2
  

The Challenge

Mezzanines can be a smart way to maximise space within existing warehouses or commercial tenancies. But they often run into compliance hurdles when the original building wasn’t designed to accommodate another level.

In this case, the proposed mezzanine addition did not meet the minimum Deemed-to-Satisfy (DTS) ceiling height of 2.4 metres. It also lacked the natural light and ventilation typically required for habitable spaces. These shortfalls raised further questions about how the mezzanine should be classified—was it a separate storey, and did it trigger additional fire safety and egress provisions?

What This Means

The NCC’s rules for mezzanines are intended to ensure that they are safe, usable, and don’t compromise the overall building’s performance. When a mezzanine doesn’t meet DTS standards for height, light, or ventilation, it doesn’t automatically mean it’s non-compliant—but it does mean that further justification is needed.

The intent is clear: even if a mezzanine is used for non-habitable purposes like storage or display, it must still provide safe movement, appropriate fire safety measures, and adequate egress for occupants. Performance solutions allow these factors to be addressed in a way that reflects the actual use and limitations of the space.

The Solution 

A performance solution was developed to demonstrate that the mezzanine could achieve the NCC’s intent despite not meeting DTS provisions. The assessment considered:

• The use of the mezzanine for non-habitable purposes
• Mechanical systems compensating for the lack of natural light and ventilation
• Safe access and egress via stairs and exits designed to NCC requirements

By addressing these key factors, the performance solution showed that the mezzanine design provided an equivalent level of safety and usability to what the DTS provisions are designed to achieve.

Why This Matters

The final report confirmed that the mezzanine addition satisfied NCC performance requirements through a performance-based pathway. This allowed the project to move forward without major structural redesigns, while still ensuring safety, accessibility, and compliance.

For designers and owners, it highlights how mezzanines don’t always have to be abandoned when DTS rules seem restrictive. With the right performance solution, they can still add valuable usable space without compromising on compliance.

Have a similar compliance issue? 

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