MBIE guidance on building product substitution

Codewords 109: October 2022

It has been well documented that Aotearoa New Zealand is currently facing a shortage of plasterboard and other commonly used building products. This is largely due to supply chain issues associated with the downstream effects of Covid-19 and elevated levels of demand. Consequently, there is an increased possibility that some building products specified as part of a building consent may need to be substituted with a similar or comparable building product.

A first principles approach

The Building Code sets the minimum performance requirements that all building work must meet. However, it does not prescribe which materials, building methods or products to use. Designers and homeowners can choose the product that fits their requirements if they can provide evidence that it complies with the relevant performance requirements of the Building Code. The below guidance provides a detailed pathway to product substitution and compliance for plasterboard and other wallboard products and is best read in conjunction with the more general Product Substitution Guidance published by MBIE in November 2021.

Product Substitution Guidance [PDF, 6.0MB](external link) – Building Performance, MBIE

MBIE’s plasterboard specific guidance

MBIE recently released the guidance document Product substitution – plasterboard for Building Consent Authorities (BCAs), designers, contractors and building owners to better support them in using building products that differ from those originally requested by owners and specified in building consent applications.

It outlines a pathway to product substitution and compliance for plasterboard and other wallboard products and is best read in conjunction with the more general Product substitution guidance published by MBIE in November 2021.

The guidance was developed in conjunction with BCAs with a view to managing the approval of plasterboard substitution in a more nationally consistent manner.

In addition, MBIE has published the step-by-step guide for plasterboard product substitution, showing the roles played by manufacturers, designers, building consent officers and builders.

Step-by-step guide for plasterboard product substitution(external link) – Building Performance, MBIE

Product Substitution - Plasterboard Guidance [PDF, 1.0MB](external link) – Building Performance, MBIE

Three-step approach

The plasterboard product substitution guidance lays out a three-step approach consistent with MBIE’s broader product substitution guidance:

• it encourages people to consider the legal context, particularly any additional obligations and compliance-related matters that might arise from a product substitution
• it points to the broader implications of using a different product to that which was specified, including whether it is fit for the same purpose and still meets the owner’s needs
• it talks people through how to implement changes to consent; for example, if substituting the product requires a minor variation or for more complex changes it might trigger an amendment to the building consent

In summary, it also:

• outlines and encourages the use of the minor variation process for substituting plasterboard
• lists those products that can be substituted as a minor variation
• explains what should be considered when substituting plasterboard that has:
  • standard performance requirements when used as lining only
  • additional performance requirements such as a substrate lining in areas subject to water splash such as bathrooms and kitchens, as an element within a fire-protection system, a sound rated system or a bracing system
  • advises what can be done in the design stage to avoid the need for product substitution, - that is, the consideration of other products and construction methods.
  • provides an appendix of links to other product information that may be of use to show compliance with the Building Code.

All parties have a role to play

The designer or builder who wishes to substitute a building product should ensure that:

• the customer is informed about, and has agreed to, the substitution taking place
• they provide adequate evidence so the BCA can be satisfied on reasonable grounds that the building work will continue to comply with the Building Code
• they are on-site to talk to the building control officer (or are available in the event it is a remote inspection) about the proposed substitution and provide documentation if requested

Failure to provide sufficient information may lead to delays in assessing variations, rejection of the application, or require an amendment to the building consent to be applied for.

Try to avoid the need to substitute in the first place

Most designers will already be trying to avoid specifying products likely to need to be substituted at the construction phase. As a reminder, however, designers should check on the availability of products that are in short supply and consider whether any of the following are more readily available and could be suitable alternatives such as:

• other readily available plasterboard products
• non-plasterboard panel systems such as plywood,
• alternative construction systems.

By Paul Hobbs, Principal Advisor, Building System Assurance, MBIE

QUIZ

1. Does a building owner need to be made aware that a building product that has been consented is to be substituted with another product?
   1. yes
   2. no
   3. maybe
2. When should the BCA be made aware of a product substitution?
   1. After the product has been substituted
   2. Before the product substitution takes place
   3. While the product substitution is taking place
3. What needs to be in place before a minor variation can be approved?
   1. Relevant technical information
   2. Applicable installation details
   3. Approval from the BCA
   4. All of the above