A White Paper on the NZ Building Code B2 (Durability) Issues, Solutions and where to from here

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1 A White Paper on the NZ Building Code B2 (Durability) Issues, Solutions and where to from here Prepared by Raed El Sarraf, Corrosion & Asset Integrity Consultant, WSP Opus Abstract The New Zealand Building Code (NZBC) sets the performance standards that all structures are required to comply with. Its main purpose is to ensure they are safe, healthy and durable for everyone who may use them. While Clause B2 applies to all aspects of a building, from foundations to pipework and electrical cables, this paper addresses B2 as it applies to a primary, load-bearing structure. The guidance given in the B1 Structures clause is clear on how engineers, and users, can both work toward its compliance (which includes a rigorous peer review process) and demonstrate how compliance can be achieved. Unfortunately, it appears that there are limitations with the B2 Durability clause of the NZBC, which has led to misunderstandings on achieving and demonstrating compliance, especially regarding Acceptable Solution s or using the Verification Methods for some common construction materials. This is especially an issue when Councils are requesting Producer Statements that are signed covering B2, but how can Engineers and Architects sign them if the means of achieving compliance is not clear? This white paper highlights the issues and challenges being experienced by Design Engineers and Architects, in meeting the expectations or requirements of Building Control Authorities (BCA). This is then followed by a proposed pathway to addressing these issues, with the aim of demonstrating compliance with the B2 Clause of the NZBC. Introduction The New Zealand Building Code sets the performance standards and means of compliance for all structures that are covered by the Building Act. While this is commonly taken as being buildings and houses, it also includes road and rail bridges, other types of infrastructure including lighting poles and even house fences. The main purpose of the Building Code is to ensure buildings are safe, healthy and durable for everyone who may use them. The guidance given in the B1 Structures clause is clear on how engineers, and users, can work toward its compliance (which includes a rigorous peer review process). Unfortunately, it appears that the B2 Durability clause of the NZ Building Code (current edition dated 1 January 2017) has some limitations; especially with regards to the use of structural steel and other metals (such as aluminium, stainless steel, etc). There are two main requirements that all structures need to meet to ensure compliance with this part of the Building Code, these are: Clause B2.2; Functional Requirement Building materials, components and construction methods shall be sufficiently durable to ensure that the building, without reconstruction or major renovation, satisfies the other functional requirements of this code throughout the life of the building.

2 Clause B2.3.1; Performance Building elements must, with only normal maintenance, continue to satisfy the performance requirements of this code for the lesser of the specified intended life of the building, if stated, or This is then followed by guidance on the period that the different building elements should be designed for, which is typically taken as 5, 15 or 50 years. It should be noted that bridges are typically taken as having an intended life of 100 years. While the above requirements are clearly stated, the guidance for using structural steel and other metals is limited. For example: There are no references to the relevant structural steel, other metals and protective coatings related durability standards within B2. There are no Acceptable Solutions for structural steel structures, the use of protective coatings and/or recommended detailing. Having said that, it is given that to satisfy the Building Code, all building elements should satisfy with what is known as the Verification method B2/VM1. However, currently this is open to interpretation and there is no guidance on how any organisations and/or practitioners become qualified to undertake steelwork (and metals) durability design. A Conundrum: Producer Statements and How to Demonstrate Compliance? Upon the completion of the design of a structure, such as a structural design to the B1 Structure Clause of the NZBC, two Producer Statements (PS) are required being: PS1 Design PS2 Design Review These documents are required to be signed by a suitably competent and qualified person. For example, upon the completion of a structural design, a PS1 and PS2 are signed by a Chartered Professional Engineer (CPEng) and/or suitably qualified practitioner on the BCA s register. These personnel have clearly demonstrated their competencies and experience to Engineers New Zealand, thus are deemed to be suitability qualified in their area of practice. When accepted by the Building Consent Authority, it can issue a Building Consent. Following construction, two further Producer Statements, PS3 Construction and PS4 Construction Review, that confirm that the design has been has been complied with are required, before a Code Compliance Certificate is issued. This is standard practice, with an accepted and clear pathway for engineers and architects to demonstrate their competency (e.g. CPEng), and a way to demonstrate compliance through the B1 Structure Clause. However, what is the pathway to demonstrating both competency for durability design, and compliance with B2 Durability?

3 At the time of writing, it is understood that discussions are being held between different organisations about why practitioners are not signing off Producer Statements for durability, and how to demonstrate compliance with the NZBC. This discussion is between the Auckland Council, Christchurch City Council, and Ministry of Business Innovation and Enterprise (MBIE) with Engineers New Zealand and the Association of Consulting Engineers NZ (ACENZ); where the Councils are requesting evidence of compliance for B2 Durability by completion of producer statements 1. Since 30 June 2017, instead of issuing a PS1, it has been recommended by Engineers New Zealand and ACENZ for engineers to issue a letter with a given format, where it clearly states: We are not able to provide a Producer Statement for durability because compliance needs to be shown on a material-by-material basis using a variety of compliance methods, and not all materials used have a clear compliance path. It then concludes with listing the relevant document for the given material. Timber is referenced back to an Acceptable Solution given in NZBC B2/AS1, concrete to NZS 3101, and steel corrosion protection to AS/NZS What this confirms is that a clearer pathway is required, not only from demonstrating compliance with the B2 Durability Clause, but also for practitioners to demonstrate their competency to be able to sign off producer statements. Proposed Pathway and Solution To address both the current limitations and the highlighted issues, the following proposed pathway is given: Review of the B2 Durability Clause To address the lack of guidance regarding the corrosion protection of structural steel, the review of the B2 Durability Clause should, as a minimum, include reference to: AS/NZS 2312 (all parts): which cover the requirements of the selection, specification, application and inspection of different types of protective coatings. AS/NZS 5131: which provides additional guidance regarding the application and inspection of protective coatings during fabrication; including guidance regarding Architecturally Exposed Structural Steelwork (AESS). This document is now cited by MBIE and will come into force from 3 July SNZ TS 3404: This technical specification provides the latest guidance for the corrosion protection of structural steel in the NZ environment, for both atmospheric and nonatmospheric environments. This document was published in February Fortunately, both NZ Heavy Engineering Research Association (HERA) and Steel Construction NZ (SCNZ) are currently in discussion with MBIE on the inclusion of the above Standards as Acceptable Solutions into the B2 Durability Clause. It is envisioned that the latest version will be issued later this year. In addition to the above, it is recommended that a durability guide, detailing issues and solutions for different materials (not just structural steel) is developed. These may also be included as Acceptable Solutions in the B2 Durability Clause or published as a supplementary document to the NZBC. 1

4 Other documents that should be referenced under the Verification Method are: HERA Report R4-97 New Zealand Weathering Steel Guide for Bridges HERA Report R4-133 New Zealand Steelwork Corrosion and Coatings Guide Finally, guidance with suitable references related to durable design in other metals, such as stainless steel is also required. Demonstrating Competency to sign off PS1 and PS2 We understand that currently there are only 2 chartered professional engineers with their practice area related to the corrosion protection of structural steel. To address the current limited number of chartered engineers in this field in New Zealand, who can sign producer statements (PS1 and/or PS2), Section 8.2 of the New Zealand Transport Agency Protective Coatings for Steel Bridges currently states: Chartered Professional Engineers who sign a Producer Statement (PS2) confirming the requirements of the B2 (Durability) Clause of the Building Code has been met, should also confirm that the specifying and detailing requirements have been met. It was deemed that to demonstrate competency, a qualified coating specifier should have, the following qualifications: NACE Protective Coating Specialist; or, Australasian Corrosion Association (ACA) Technician or Technologist with successful completion of the ACA s Coating Selection and Specification Course and/or certified to NACE Coating Inspection Program (CIP) Level 2. Based on the above, it is recommended that a similar qualification requirement is considered by Engineering New Zealand when a competency pathway is developed. Of course, this needs to be associated with relevant tertiary and specialist training qualifications and industry experience. Due to the diversity of pathways possible (either from an engineering or scientific background), it is suggested that they be identified as Chartered Professional Durability Practitioners. Signing off PS3 and PS4 PS3 is related to completion of the building work, which in this case is mainly related to the correct application and installation of the corrosion protection systems on steelwork. While PS4 is related to the construction monitoring of the building work, in this case verifying that the specified systems were installed, usually by ensuring that the relevant quality assurance process was followed. For issuing of a PS3, the following minimum requirements are recommended: Coating applicators to work within an effective quality assurance system and employ trained and experienced blaster/painters and supervisor/inspectors, and have well maintained plant and facilities. Depending on the structures complexity (such as a bridge or AESS steel) and site corrosivity (such as C3(Medium)), to be aligned with the requirements of AS/NZS 5131 and SNZ TS 3404, the painting applicator should be accredited under the Australian Painting Contractor Certification Program (PCCP). This is currently a requirement for NZTA bridge painting. Only coatings approved by an independent body such as the Australian Painting Approval Scheme (APAS), the North East Protective Coating Committee (NEPCOAT) or Norsk Sokkels Konkuranseposisjon (NORSOK) shall be used on critical structures in severe environments ( C3(Medium) to ISO 9223).

5 For issuing of a PS4, the following minimum requirements are recommended: The use of an inspector certified by the NACE Coating Inspector Program or a Protective Coatings Inspector with a current Competence Certificate issued by the Certification Board for Inspection Personnel NZ (CBIP). It is important that the inspector s independence from the physical works and coatings contractor is maintained. Again, this will not be required for all projects, for example painting a home garage/shed a qualified coating inspector is not required; however, when painting a stadium, it should be. Once the inspectors report is issued, a chartered design engineer and/or a chartered durability practitioner can then issue a PS4. Other Materials While the above pathway recommendations and reviewing of the NZBC are mainly related to structural steel, a similar review and pathway may be required for other construction materials. For example, most of the durability design requirements for concrete are clearly given in NZS However, for situations that are beyond those given in that Standard, a specific durability design will be required. This should be undertaken by a competent concrete specialist; however, we understand that there is not yet a pathway for such personnel to demonstrate their competency in this specialist field. A review of how material specialists can demonstrate their competency is recommended. Potential Timeline As discussed earlier, the revised B2 Durability Clause is expected to be released by the end of However, the other recommendations given above are expected to take longer depending on the time required to develop the competency pathways, and contractors and suppliers achieving the required accreditations and qualifications (such as PCCP and APAS). It is envisioned that the development of the competency pathway with Engineering NZ, may take up to a year. After which, the current experienced materials specialists and engineers should attain the Chartered Professional Durability Practitioner status. For new entrants to this field, it is expected to take them at least 5 years (post tertiary qualification) before they can demonstrate competency. This is a similar timeframe to current CPEng requirements for other engineering fields. As for contractors and suppliers, this depends on the status of their current Quality Assurance and Control systems. Their required accreditations may be achieved within a number of months to a year. In summary, while a revised version NZBC B2 Durability Clause is expected by the end of year; it should be accepted by the relevant organisations that there will be an interim period before a comprehensive compliance system is put in place. Cooperation, and patience, between the different parties is required, and the sooner this work is started the better. How will this work in practice? While the above proposal outlines a compliance and competency pathway that may be used for all types of structures, in practice it is not expected that a chartered durability practitioner will be required to sign off a PS1/PS2 in all cases. It is envisioned that for common structures (such as low to medium-rise buildings), typical durability related matters will be addressed via the relevant material standard and B2 (Durability Clause) Acceptable Solutions. As such, design engineers who demonstrated compliance with NZ Building Code in this manner, are not expected to require a chartered durability practitioner to sign off PS1/PS2.

6 It is envisioned that this sign off will only be required, for situations that are beyond those given in the material standard(s) and Acceptable Solutions, especially when using the Verification Method. Conclusion It has been recognised by the engineering fraternity that that there is a lack of guidance on demonstrating design compliance with the NZ Building Code B2 Durability Clause. This not only relates to the B2 Durability Clause itself but also for practitioners to demonstrate their competency and a pathway to becoming a Chartered Professional Durability Practitioner in their chosen materials related practice area is required. This paper outlines the issues and proposes a number of solution to address this matter. This includes the following recommendations: Review NZ Building Code B2 Durability Clause and incorporate suitable standards and references for the corrosion protection of structural steel. This is currently underway. Outline the minimum qualifications required for the practitioners to undertake the durability design and peer review for the corrosion protection of structural steel; from which design Producer Statements (PS1 and PS2) may be issued. Outlines the minimum requirements for coating applicators, coating inspectors and the coating itself, from which construction Producer Statements (PS3 and PS4) may be issued. A review of the pathways to achieving a Chartered Professional Durability Practitioner qualification for material specialists and engineers, not just for structural steel but other materials such as stainless steel and specialist concrete. While the revised B2 Durability Clause is expected by the end of 2018, further work is required to develop and implement the recommended solutions and pathway. Cooperation between the different parties is required to ensure the timely implementation of a comprehensive compliance system. References AS/NZS 2312; Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings. Standards New Zealand. Wellington NZ. 2002/2018. AS/NZS 5131:2016; Structural steelwork Fabrication and erection. Standards New Zealand. Wellington NZ. El Sarraf, R and Clifton, G.C.; New Zealand Steelwork Corrosion and Coatings Guide. HERA Report R HERA. Manukau, New Zealand Engineers New Zealand/ACENC Producer Statement Letter; ISO 9223:2012; Corrosion of metals and alloys- Corrosivity of atmospheres- Classification, determination and estimation. Geneva, Switzerland. Mandeno, W. and El Sarraf, R; Protective Coatings for Steel Bridges. New Zealand Transport Agency. Wellington, New Zealand. April NZ Building Code B1 Structures; MBIE, Wellington, New Zealand. 3 April NZ Building Code B2 Durability; MBIE, Wellington, New Zealand. 1 January NZS 3101:2006; Concrete structures Standard. Standards New Zealand. Wellington NZ. SNZ TS 3404:2018; Durability requirements for steel structures and components. Standards New Zealand. Wellington NZ. Zaki, R, and Clifton, G.C; New Zealand Weathering Steel Guide for Bridges. HERA Report R4-97. HERA, Manukau, New Zealand. 2005