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The New Zealand Building Code is a performance-based legal document which provides the performance requirements that all buildings must meet to be built in New Zealand. To encourage competition and innovation, and to enable designers and building owners to take a design-led approach in proposing the best solution for their project, any construction method or material may be proposed as part of a building consent if you can demonstrate HOW it will meet the performance requirements in the Building Code.
What is an Alternative Solution?
An alternative solution is a means of demonstrating how your building work will meet the performance requirements of the Building Code. An alternative solution will include any product, component, construction method or detailing that makes up a building design or part of a building design that complies with the performance requirements of the Building Code and is NOT included under an Acceptable Solution or Verification Method.
This includes a large swathe of modern building materials and methods; the Acceptable Solutions tend to have a restrictive scope and limitations on building types and construction methods that they cover. Nearly all building projects, particularly complex projects or renovations and upgrades to existing buildings will include alternative solutions as they will likely include building and construction techniques that are outside the scope of the Acceptable Solutions or Verification Methods.
Construction methods, materials and techniques that are included within the Acceptable Solutions and Verification Methods are considered ‘deemed to comply’, meaning that the Building Consent Authority (BCA) must accept these solutions as meeting the performance requirements of the Building Code when assessing a building consent. They are used, most often, because they are considered easy methods for getting a building consent given the BCA must automatically accept them. However, they are not the only means of compliance and alternative solutions proposed with an adequate level of supporting documentation can also be easily consented.
There are many reasons for owners, designers and engineers to want to use methods and materials considered alternative solutions, such as functional or aesthetic reasons, limitations of the building site or existing building or wanting to achieve a higher quality of a building than the acceptable solution prescribes. A perceived difficulty with getting alternative solutions consented should not prevent designers from using high quality materials and methods that meet the performance requirements of the Building Code.
The BCA will have an established procedure for assessing any proposed solution and must be satisfied on reasonable grounds that any proposal meets the performance requirements of the Building Code. To do this they will examine the evidence provided and likely consider this against what is known to comply. BCAs are required to record in detail all their decision making and how they have determined they have reasonable grounds to grant a building consent. They rely on owners, designers, and product manufacturers to meet their own responsibilities under Section 14 of the Building Act so that they can form these reasonable grounds and easily make and record these decisions.
MBIE’s recent ‘Satisfied on Reasonable Grounds guidance’ provides the below advice;
‘In contrast to an Acceptable Solution or Verification Method, the methodology and burden of proof employed to illustrate compliance of an alternative solution under a performance-based Building Code sits with the designer or with those specifying a building product or building method. It is for these parties to demonstrate that all applicable Building Code performance obligations have been met. In order for proper performance-based evaluation and assessment to follow, it is critical that the evidence base for complex alternative solutions is both clear and robust’.
This guidance and Simpli’s new Alternative Solution Summary Form is designed to assist applicants with presenting their evidence and communicating their proposed solution to the BCA, to give a clear understanding of what is trying to be achieved and how the proposed solution performs and complies. This will assist the BCA with assessing the compliance of the proposed solution and create a common language between BCAs and applicants to streamline the building consent process and reduce Requests for Information (RFIs).
What are accepted means of demonstrating compliance as an alternative solution?
Comparison to Acceptable Solutions or Verification Methods
Acceptable Solution and Verification Method compliance documents are developed to include familiar, common and tested construction methods and techniques therefore it often makes sense that alternative solutions are variations of methods included in these documents. If the variation from the acceptable solution is minor in nature then making a comparison to the valid compliance criteria from the acceptable solution is useful rationale for explaining the performance of the proposed solution.
When identifying similarities to the acceptable solution, it is important to also explain the differences. An alternative solution, by definition, will vary from the acceptable solution, so what is the variation and how have you ensured that this variation maintains the same level of performance or better than the acceptable solution? It is always helpful to explain the rationale behind the proposed solution and why it is most appropriate for your overall design.
Codemark Certificate or BRANZ Appraisal
Products and building systems that have CodeMark Certificates are a deemed-to-comply pathway, meaning, as long as the product is used with the scope of the Certificate and specified in accordance with the limitations of the certificate Building Consent Authorities must accept the product as complying with the Building Code.
Other product certification schemes, such as BRANZ Appraisal, are often considered a simple and familiar compliance pathway as long as the certification scheme is trusted in New Zealand and most BCAs will accept this certification as reasonable grounds to approve the alternative solution. Once again, the product must be used within the scope of the certification or appraisal and in accordance with its limitations for it to be accepted without any additional evidence provided.
One of the most common alternative solutions presented to BCAs is products used outside the scope of their certification or appraisal. If the applicant wishes to use the product outside the scope of its certification or appraisal, perhaps because the site conditions are not comparable to the conditions the product was tested to for certification or the applicant wants to use the product in a new or innovative use not specified by the manufacturer, then additional evidence, beyond just the certificate or appraisal, will need to be provided to demonstrate compliance.
This evidence will need to demonstrate how you are compensating for the differences from the certification, for example using large flashings with additional fixings if the system is being used in a wind zone higher than that with which it was certified for, or comment from the product manufacturer/supplier or certification/appraisal body on your proposed specification of the product
Depending on the level of variation, this evidence may need to include expert opinion from the product manufacturer as to whether they would support the use of the product in the specified scope and whether they still think it would meet the requirements of the Building Code.
In-service History
In-service history is a compliance pathway for products, systems or construction methods with a proven track record of compliance. This compliance pathway is often used to show the performance of historic or uncommon products or methods of construction or methods that are no longer considered best practice, such as direct fixed cladding, but are proven to perform in specific situations.
To use in-service history as a compliance pathway there must be a documented history of effective performance over a significant period of time. If the performance requirement is weathertightness, for example, the product must be demonstrated to have complied for a minimum of 15 years, the durability period required for such products.
Remember, when using in-service history as a compliance pathway, the proposed solution and existing site conditions must be comparable to the existing situation you are using to show the performance of the solution. This requirement makes this compliance pathway most appropriate and particularly effective when undertaking additions and alterations to an existing building where the solution is already in use.
Expert Opinion
There is a range of expert opinions that can be provided to support an alternative solution. The level and detail required of the opinion by the BCA will likely depend on the complexity of the building and solution proposed.
Types of expert opinions may vary, from short written statements by designers or product experts making comments with their areas of expertise, to testing, models, simulations, calculations and written reports carried out by technical experts qualified to carry out these assessments.
For minor deviations from the limitations of the product certificate or acceptable solution a statement from a technical product expert or qualified designer may be sufficient to show compliance in combination with necessary warranties and product certificates or appraisals.
For more complex alternative solutions a specialist consultant may be more appropriate to support the proposal, for example an engineer or technical specialist. The expert opinion must be specific to the proposed building and solution and be supported by the necessary qualifications or credentials. This opinion can have added credibility if a memorandum or producer statement is provided covering the scope of the opinion or design and demonstrating the qualifications of the specialist.
It is still up to the BCA to assess and accept the credentials of your specialist, they do not have to accept producer statements and may require more information or a peer review to be reasonably satisfied that the opinion and solution provided will comply with the Building Code. If you are proposing a complex solution that will rely on expert opinion to demonstrate compliance you should speak to your BCA before submitting your consent to discuss the specifics and what the BCA may require to remove the risk of the opinion and solution being rejected later on in the process.
Comparison to a Determination
An alternative solution may be supported by an MBIE issued determination. MBIE determinations are essentially a dispute resolution process allowed for under the Building Act where MBIE will make a ruling, generally between a BCA and building owner, although not always, on the interpretation of a Section of the Act or compliance with the Building Code. Proposing an alternative solution that previously received a positive determination outcome is a deemed to comply pathway that BCAs must accept.
Like product certifications, however, MBIE determinations are often project specific and limited in scope. If you are using a determination to support the compliance of your alternative solution it is often helpful to provide a summary explanation as to why the determination supports your solution, acknowledging the similarities and also any differences in scope and how the determination supports the compliance of your solution. This supports BCAs in their decision making and being satisfied on reasonable grounds that your solution meets the conditions of the determination and is therefore deemed to comply.
If your proposed alternative solution has been accepted previously by the same BCA or another BCA around the country this can also be used to support the compliance pathway of your solution but the same advice as above applies. You will need to provide the situation that it was previously accepted in, and if there are any, acknowledge the similarities and differences and how your proposal complies in the same manner.
Differences in ‘Minor alternative solutions’ and complex alternative solutions?
As already stated above, there are many alternative solutions which are common and used frequently. These solutions usually have a recorded history of performance and are considered to comply using a combination of pathways laid out above, namely inservice history and comparison to acceptable solutions or verification methods. Because the solutions are common and familiar to the BCA and consenting officers it is likely that the BCA will require less information for these solutions.
Examples of common, frequently used alternative solutions may include:
- Specifying exterior timber or uPVC joinery with detailing comparable to or outside the scope of E2/AS1. These alternative joinery materials have been used for decades in New Zealand and any variance from the Acceptable Solution is usually minimal. Given the prevalence of these joinery types these are considered a comparable component or assembly with a range of acceptable details able to meet the Building Code performance requirements of E2
- Junction details between different cladding types are outside the scope of E2/AS1 and often outside the scope of manufacturers certified details, however these details are often comparable to acceptable solutions or certified manufacturers details and require little additional explanation to demonstrate compliance
- Vertical profiled metal cladding on a cavity is outside the scope of E2/AS1, though like many other modern, widely used cladding products installed over cavity, it is generally considered to likely exceed the requirements of the acceptable solution and comply with the performance requirements of the Building Code
- Standard proprietary shower cubicles not to E3/AS1. The details in E3/AS1, circa 1998, are outdated compared to modern cubicle profiles and installation. However, the general design principles and detailing of these cubicles is comparable and widely accepted to meet the requirements of the acceptable solution.
These types of alternative solutions are often called ‘minor’ or ‘low-risk’ alternative solutions, but they are still alternative solutions and the responsibility and burden-of-proof to show how these solutions will comply is still on the designer or building consent applicant. If you are unsure what level of information you will need to provide, we recommend starting at least with a summary sheet, describing the solution and how it will meet the performance requirements of the code with any relevant evidence. Alternatively, you can speak to someone at your BCA about your solution and what evidence they may require before submitting your building consent application.
Designing your Compliance Solution
MBIE as part of their Alternative Solution Guidance recommend undertaking the following steps for assessing the compliance pathway of your design and gathering the necessary evidence to demonstrate compliance.
This process should be undertaken at every step in the design process (concept, developed and detailed design etc.), understanding the compliance pathway for your proposed solution needs to be understood and the required evidence planned early in your project. It can be difficult to source the required evidence once the design is complete or after the building consent has been submitted and this will often add time and cost to the project. Scope your potential alternative solutions early in your design and speak to a specialist consultant or your BCA to establish the level of evidence that will be needed so that all parties are satisfied that the proposed solution complies with the performance requirements of the Building Code.
- Scope the project
Determine which parts of the project are not covered by an acceptable solution or verification method. These parts require an alternative solution. - Identify the Building Code clauses
Include the specific performance requirements for each Building Code clause. - Provide Evidence
Your documentation must contain sufficient evidence to show the identified performance criteria of all relevant clauses will be met. The amount of evidence may be significant, depending on the complexity of the project. - Present your Evidence
Provide a strongly argued case to the BCA by including as many of the above tools as possible. Be sure to state exactly what Building Code clauses and performances are being addressed. The clearer the supporting documentation, the easier the evaluation of it will be. - A Building Consent Application is Accepted when Compliance is clearly established
All of the evidence, as described above, is assessed. Note that outside help may be sought by the BCA in assessing all, or specific aspects, of a proposed alternative solution.