Wall Construction

Structural Compliance in Portable Homes

NCC 2022 Volume 2

Area of NCC Requirements:

• Section H
  

The Challenge

Portable and prefabricated homes are becoming increasingly popular as flexible and efficient housing solutions. But with new methods of construction often come unexpected compliance challenges.

In this case, an inspection revealed that different wall battens and screw fixings had been used instead of those specified in the approved cladding system. On paper, this substitution fell outside the Deemed-to-Satisfy (DTS) provisions of the NCC, raising concerns about structural performance, durability, and long-term compliance.

What This Means

The NCC’s structural provisions exist to ensure that buildings—whether permanent or portable—remain safe and fit for purpose over their service life. Even seemingly minor variations, like different battens or fasteners, can affect weatherproofing, load transfer, and overall wall performance.

When construction deviates from DTS provisions, the responsibility shifts to demonstrating that the system still meets the intent of the NCC. That means showing that alternative materials, when used correctly, deliver equivalent safety, structural adequacy, and durability to the prescribed solution.

The Solution 

A performance solution was developed to assess the substituted wall battens and fixings. The assessment involved:

• Expert judgement and comparison with NCC structural requirements
• Consideration of the protective role of external cladding and insulation wrap
• Conditions around installation to ensure the substitutions performed as intended

This approach demonstrated that, when installed under controlled conditions, the alternative system still delivered outcomes consistent with the NCC’s structural performance intent.

Why This Matters

The final report confirmed that the alternative materials complied with NCC requirements for this project, provided they were installed to the specified standards. Importantly, the approval applied only to the current build—future projects must follow original manufacturer guidelines or undergo their own performance assessments.

This case underscores how performance solutions can provide a compliance pathway when real-world substitutions arise, keeping projects on track without compromising safety or quality.

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