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Building Controls Update

Codewords Issue 048 - August 2011

This issue of Codewords is dedicated to changes to the Building Code supporting documents that came into effect in August 2011.

Changes are significant and affect building structure and external moisture documents. In addition, new guidance documents have been introduced for barriers, reinforcing of concrete slab-on-ground floors, and building on soils subject to liquefaction.

Revised Building Structure documents

Image of steel framing Changes to key Building Code documents that deal with building structure took effect on 1 August 2011.

The changes involve important documents like the Standard for timber framed buildings NZS 3604:2011, and building officials, designers and architects, builders and engineers need to be aware of them.

What is new in Acceptable Solution B1/AS1

The Acceptable Solution B1/AS1 now references NZS 3604:2011, the latest version of this Standard which replaces the 1999 version.

NZS 3604 is used to design most homes and other low-rise timber-framed buildings in New Zealand.

Standards New Zealand updated the Standard to align it with the loadings Standard AS/NZS 1170, particularly with regard to wind, earthquake and snow loads.

The limited technical review of the Standard was also aimed at reflecting current construction practices, and simplifying and clarifying the document.

For example, new diagrams clarify how to determine loaded dimensions and spans, while durability requirements have been clarified by new tables and diagrams describing exposure conditions.

NZS 3604:2011 is also aligned with the revised Acceptable Solution for weathertightness for timber-framed buildings, E2/AS1 (see article Changed External Moisture Documents).

There are important modifications. Changes made for the Canterbury Earthquake Region on 19 May 2011, requiring all slabs-on-ground to have reinforcing mesh which is tied to perimeter foundation reinforcing, now apply to all parts of the country. Unreinforced concrete slabs-on-ground are no longer an option anywhere (see article Changes to Concrete Slabs-on-Ground).

However, the amended definition of good ground for the Canterbury Earthquake Region , excluding ground subject to liquefaction or lateral spread, still only applies to that region.

Building officials and designers need to familiarise themselves with the changes throughout the new NZS 3604:2011, as well as the changes to Acceptable Solution B1/AS1. Some key changes are:

Only verified timber grades can be used with NZS 3604:2011. All structural timber will now be known as structural grades SG6, SG8 and SG10 - for example, SG8 now collectively refers to both machine stress grade 8 (MSG8) and visual stress grade 8 (VSG8).
Section 11 content (which related to the Building Envelope) has been removed and is now covered by E2/AS1. Section 11 now just references E2/AS1. So now NZS 3604 provides a structural solution while E2/AS1 provides a weathertightness solution for that structure.
A new “Extra High” wind zone with 55 m/s wind speed has been added. Previously, the highest wind zone was “Very High” at 50 m/s. The inclusion of the “Extra High” wind zone has resulted in changes to the sections dealing with bracing, and wall and roof framing.
In the scope and interpretation, the classification of buildings has been expanded to interpret and conform to the importance level classification in the loadings standard AS/NZS 1170.
Engineered wood products laminated veneer lumber (LVL) and glued laminated timber (glulam) have been introduced to the Standard.
The Scala penetrometer test method for determining good ground has been revised to reflect the dimensions of the penetrometer equipment used in New Zealand.
Exposure zones have been revised. Also, a new clause on microclimatic considerations requires Specific Engineering Design (SED) for industrial and agricultural contamination and geothermal exposure.
Fixings and fasteners of exposed framing in Zone D (the zone for coastal and sea spray areas) are now required to be stainless steel .
Steel fixings and fastenings in exposed or sheltered locations, in contact with timber treated with high copper-based preservatives, need to be a minimum of stainless steel.
Durability information relating to flashings, underlays and associated materials, has been removed and is now covered by E2/AS1.
For wind bracing, the previous tables for all wind zones have been simplified by a single table for the “High” wind zone, with factors for designers to calculate the requirements for other wind zones. Similarly single tables based on earthquake zone 3 and soil type D/E are provided and can be used to calculate bracing requirements for other earthquake zones and soil types.
Earthquake zones have been renamed and reflect the new seismic hazard profile of the country.
For bracing, the bracing capacity of proprietary bracing systems used in accordance with NZS 3604 has been limited to:
- 120 BU/m on timber-framed floor
- 150 BU/m on concrete slab or concrete perimeter wall.
Also, the Standard has a new requirement to evenly distribute bracing elements within the building.
For concrete slab-on-ground floors, provisions for fixings of bottom plates to the floor have been revised.
For wall framing, stud spacing is now at 300, 400 and 600mm centres.
For roof framing, roof trusses require Specific Engineering Design (SED), but roof trusses meeting the requirements specified in the normative part of the Standard and manufactured by an accredited manufacturer are now part of the Acceptable Solution.
Snow zones have been revised. All tables for wall and roof framing now incorporate a 1kPa snow loading. Additional tables are provided in the Appendix for 1.5kPa and 2kPa snow loading.
Snow loads now include increased loads from snow drifts formed against upper walls on lower roofs.

What is new in Verification Method B1/VM1?

The Verification Method B1/VM1 references two new documents:

NZS 4219:2009 Seismic performance of engineering systems in buildings. This Standard deals with restraints for engineering systems to protect them from being dislodged, disconnected or damaged in an earthquake. This includes tanks, piping systems, ducting and mechanical and electrical services. The Standard is modified in B1/VM1 by amending the seismic hazard factor and the component risk factor for the Canterbury Earthquake Region. NZS 4219:2009 supersedes NZS 4219:1983.
NASH standard ‘Residential and Low-Rise Steel Framing Part 1: Design Criteria: October 2010. This document is a design standard which addresses how to comply with the performance criteria of Building Code clause B1 for steel-framed low-rise buildings such as houses and commercial buildings. It has been published by the National Association of Steel-framed Housing (NASH).

What else has changed in the B1 documents?

There are changes to documents covering barriers, which are outlined in another article (New Barrier Guidance Document).

What are the transition arrangements?

The changes to the B1 documents took effect on 1 August 2011. From that date, there is a transition period to 31 January 2012, when both the previous (amendment 10) and the new (amendment 11) versions of the documents can be used. From 1 February 2012, only the new versions of the B1 documents can be used as Acceptable Solutions or Verification Method.

The changes for Canterbury were first incorporated in the previous version of the B1 documents (amendment 10). This means that these changes apply for Canterbury regardless of whether the new or previous version is used in the transition period.

Changed External Moisture documents

Key Building Code documents dealing with the weathertightness of buildings have changed.

The changes affect important and much used documents like Acceptable Solution E2/AS1.

They reflect the latest studies and research, respond to changes in building practices, bring the documents into line with the latest Standards, and introduce a new solution for concrete and concrete masonry.

What are the major changes to E2/AS1 and E2/VM1?

E2/AS1 is the widely used Acceptable Solution for the building envelope of timber-framed houses and is a companion document to NZS 3604 Timber-framed buildings. E2/VM1 is the Verification Method contained in the same E2 Compliance Document.

The Acceptable Solution has been changed to reflect the latest research and changes in building practice and to introduce new information about methods of cladding.

The document has been simplified to work better with the new NZS 3604:2011 and to make it more useful for industry, but the format has been retained to make it easy for regular users to identify the changes.

Major changes to E2/AS1 involve:

Wind zone limits, which have been extended from a maximum upper limit of 50m/s to 55m/s
height definitions
inclusion of attached garages
introduction of rigid air barriers for higher wind zones
definitions of ‘exposed’ and ‘hidden’ flashings
inclusion of sill supports for cavity construction
inclusion of door sills and removal of restrictions on opening types
openings in direct fixed claddings
parapets and enclosed balustrades.

Users of E2/AS1 will discover that although the information is retained in its familiar format, some significant changes have occurred. Most noticeable is the extension of the wind range to 55m/s. This will enable the inclusion of a greater number of buildings within its scope. In addition is a clarified facility for designers of buildings in wind ranges beyond the new ‘Extra High’ category. Design details beyond the 55 m/s range of E2/AS1 can be tested using the updated E2/VM1 up to a ULS design wind pressure of 2.5 kPa (approximately 63 m/s).

The update to E2/AS1 reflects the trend within industry towards the wider use of drained cavities. E2/AS1 now requires cavities for all parapets, enclosed balustrades, monolithic claddings (EIFS, stucco, flush-finish fibre cement), and for buildings in the new Extra High wind zone.

There are also changes to allow for the use of flat sill trays for direct fixed windows and doors (to make installation easier), the use of jamb battens for direct fixed joinery, and changes to allow specific designs to be used within the E2/AS1 framework.

From 1 August 2011 to 31 January 2012 both the new version with Amendment 5 and previous version of E2/AS1 and E2/VM1 apply, and can be used when making applications for building consent.

From 1 February 2012, only the new version of E2/AS1 applies.

Designers will need to consult the E2 Compliance Document for full information on designing for external moisture management.

Weathertightness for concrete

Weathertightness solutions for concrete houses and small non-residential buildings are given in a new Acceptable Solution, E2/AS3.

E2/AS3 references the Code of Practice for Weathertight Concrete and Concrete Masonry Construction, recently published by the Cement and Concrete Association of New Zealand (CCANZ).

It covers how to ensure the weathertightness of:

concrete slabs-on-ground and footings
concrete walls
concrete low-slope roofs and decks
junctions between walls, roofs and floors; and concrete to timber junctions.

CCANZ CEO Rob Gaimster says it will enable the weathertight advantages of concrete and concrete masonry systems to enhance New Zealand’s building stock.

“E2/AS3 will contribute greatly to alleviating building consent authority uncertainty in the area of weathertight concrete and concrete masonry design, and in turn, allow for a more inclusive range of building materials from which builders, designers and their clients can choose.”

Weathertight systems covered in the Acceptable Solution

Systems for concrete masonry walls, in-situ concrete walls and precast concrete walls are covered in the solution and comprise an EIFS (Exterior Insulation and Finish System), plaster systems, masonry veneer, coating systems or watertight concrete. Table 1 shows the options.

Image of table 1 which shows the different options for weathertight systems

Weathertight details are provided for walls and roofs or decks with thermal insulation in different positions including:

on the outside of the wall/roof (ie, EIFS or exterior)
within the wall/roof structure (ie, integral)
and on the interior face of the wall/roof structure (ie, internal).

The Acceptable Solution also includes:

details for openings and penetrations through walls such as windows and doors
footings and concrete slabs on ground, which are made weathertight using DPMs (damp proof membranes) described in the Standard for the non-specific design for concrete masonry, NZS 4229:1999
weathertight systems for concrete roofs and decks, using either EPDM or butyl rubber membranes or bituminous membranes.

The document does not provide any structural solutions, but some structural design requirements are specified because the weathertightness systems rely on having a stable concrete or concrete masonry substrate. These include:

concrete masonry walls must be designed using the non-specific design standard NZS 4229
insitu and precast concrete walls must be specifically designed to limit cracking in the wall surface
concrete slabs on ground and footings must be designed either using the non-specific design standard NZS 4229, or specifically designed to limit cracks in the slab and footing
roofs, decks and parapets must be specifically designed to limit cracking in the concrete surface.

Who will benefit from the changes?

E2/AS3 will give designers of concrete and concrete masonry buildings greater confidence that their designs will comply with Building Code clause E2. Designers using the Acceptable Solution will need to specifically design elements of the building where E2/AS3 does not provide an explicit specification.

Building consent authorities (BCAs) will be able to quickly and easily approve designs that comply with E2/AS3, provided elements of the building that require specific design are properly specified.

E2/AS3 describes standard maintenance procedures for products used in the weathertightness systems, including inspection and replacement intervals.

Copies of the Code of Practice for Weathertight Concrete and Concrete Masonry Construction can be purchased or downloaded online at www.ccanz.org.nz.

What are the transition arrangements?

The changes to the E2 documents took effect on 1 August 2011. From that date, there is a transition period to 31 January 2012, when both the previous and the new versions of the documents can be used. From 1 February 2012, only the new versions of the E2 documents can be used as Acceptable Solutions or Verification Method.

New Barrier Guide

Image of houses with timber barriers A new guidance document for barriers will be published by the Department shortly and the current Acceptable Solution for timber barriers, B1/AS2, will be discontinued on 31 January 2012.

The guidance document incorporates loadings from AS/NZS 1170, Structural Design Actions, and will cover the range of materials that are now being used. Most barriers currently being built are of materials other than timber such as glass and metal.

The guidance document will replace B1/AS2 which only provides a solution for timber barriers based on loadings specified in the superseded NZS 4203:1992.

It will address a range of areas including barrier geometry, loadings, deflection limits, and testing procedures to prove a design’s performance. It will also provide information for barriers constructed of timber, glass and metals, and include a useful checklist for building consent application checking at the end of the document.

It has been developed by a working group of structural engineers and specialists from the design, manufacturing and construction industries, in consultation with a number of industry participants.

The Department plans to publish the Barrier Guide in August 2011. It will be available on our website.

Changes to concrete slabs-on-ground

Image of the construction of a concrete foundation Stronger foundations are now required throughout New Zealand, following changes to Building Code documents on 1 August 2011. Unreinforced concrete slabs-on-ground are no longer included in the Acceptable Solution B1/AS1. Concrete slabs-on-ground on good ground must now have reinforcement which is tied to perimeter foundation reinforcement.

Only Ductility Class E reinforcement is part of the Acceptable Solution. The reinforcing for concrete slabs-on-ground is now a minimum of 2.27kg/m2 of Grade 500E reinforcing mesh fabric which complies with AS/NZS 4671.

Currently Grade 500E reinforcing mesh of this specification is not yet available from any suppliers in New Zealand. Therefore, the Department of Building and Housing has published guidance on alternative solutions to provide time for manufacturers to produce Grade 500E reinforcing mesh.

Alternative solution using mesh:

Lower yield strength steel mesh than Grade 500E can be used if an equivalent tensile capacity in the slab can be achieved. The amount of steel (kg/m2) necessary to achieve the equivalent capacity is determined as 2.27 x 500/Strength Grade of steel (where the strength grade of the steel is the verified lower characteristic yield strength of the steel bar in MPa). The uniform elongation Agt (refer Table 2 of AS/NZS 4671) must equal or exceed 10%.

Alternative solutions using reinforcing bars:

Grade 300E – D10 reinforcing steel bars at 300mm centres each way with 30mm top cover, or
Grade 300 – D12 reinforcing steel bars at 450mm centres each way with 30mm top cover.

Read the updated B1/AS1 Acceptable Solution.

For full details on the alternative solutions consult the Department’s Guidance on Reinforcement for Concrete slabs-on-ground.

New CodeMark product certification body earns its stripes

Product certification (brand name CodeMark) has been given a substantial boost with the appointment of a second product certification body, SAI Global, and its issue of New Zealand’s second CodeMark certificate for The Laminex Group’s Metaline Splashback.

Global-Mark Pty became the first product certification body here earlier last year, while James Hardie became the first New Zealand firm to receive a CodeMark certificate, for its Linea weatherboard, in September 2010.

CodeMark is a voluntary scheme that provides an easily-understood and robust way to show a building product or system meets the requirements of the New Zealand Building Code. The Laminex Group and James Hardie now enjoy the certainty that their CodeMark products must be accepted as Code-compliant by building consent authorities – as long as these products are used and installed as their CodeMark certificates specify.

John Gardiner of the Department of Building and Housing says SAI Global’s appointment and the issue of a second CodeMark certificate are very positive steps for the New Zealand market.

“One of the main aims of CodeMark was to lift standards of building quality and performance, so it is encouraging to see a growing appreciation of the scheme’s benefits,” John says.

“While it may not be the right choice for every building manufacturer or supplier, seeking CodeMark certification can make good business sense not only in terms of Code compliance but also to provide a marketing advantage.

“The Laminex Group’s CodeMark application here, after already being certified in Australia, underscores the recognition this scheme now has on both sides of the Tasman.”

The CodeMark scheme was developed jointly by the Department of Building and Housing and the Australian Building Codes Board, and operates under the CodeMark brand name on both sides of the Tasman. However, products must be certified separately for New Zealand and Australia because of differences in the two countries’ building codes.

Product certification bodies - such as Global-Mark and now SIA Global – are the only organisations that can assess building products or systems for CodeMark. Product certification bodies must first be assessed and accredited by JAS-ANZ (Joint Accreditation System of Australia and New Zealand).

John says the Department is continuing to work with product certification bodies and prospective applicants as CodeMark certification and branding becomes increasingly visible. At present, around 15 New Zealand manufacturers and suppliers are either working through their applications or are actively considering CodeMark.

Read more about Product Certification (CodeMark).

Determination 2011/035: The refusal to issue a code compliance certificate due to reasonable progress not having been made

The determination arose from a decision of a Building Consent Authority (BCA) to refuse to issue a code compliance certificate for a building. The BCA was of the view that reasonable progress had not been made in respect of the time taken to construct the building. The determination therefore considered whether the authority correctly exercised its powers when it decided to refuse to issue the code compliance certificate.

The parties to the determination were the owner of the building and the BCA. The owner applied for the determination.

Background

A building consent was issued by the BCA in 2002 under the Building Act 1991 for the construction of the building. Between 2002 and 2005, the BCA carried out various inspections of the building work. The BCA subsequently carried out two final inspections in 2010 and 2011.

The BCA was of the view that the building work “had been completed satisfactorily” and complied with the requirements of the Building Code that were in effect when the building consent was issued. The authority was also of the view that the reasonable progress provisions of the Building Act 1991 applied and that “it was difficult to accept that reasonable progress has been made here given the time between inspections”.

Discussion

The determination considered whether it was appropriate for the BCA to refuse to issue a code compliance certificate based on a lack of reasonable progress.

The question of reasonable progress had been considered previously, in Determination 2010/057, which involved the same BCA. Under section 41(1)(b) of the Building Act 1991, the reasonable progress provision concerns the failure to make reasonable progress on building work within 12 months after work commences, or within such further period as the discretion of the BCA may allow. Determination 2010/057 found that the reasonable progress provision was not relevant to any other delay between the issue of a building consent and when a final inspection is requested. Further, it was to be applied when reasonable progress is not being made, not at some point after this when the building work has been completed. Therefore, a BCA would need to take action within 12 months after the issue of a building consent (unless a further period had been allowed).

The determination found that the views set out in Determination 2010/057 were applicable to this situation, and that the relevant period of delay was not a ground under section 43(5) of the Building Act 1991 for refusing to issue a code compliance certificate, had that Act been in force.

The BCA, in its final inspection of the building, took the view that the building work complied with the Building Code. The determination therefore concluded that the BCA was satisfied on reasonable grounds that the completed building work complied with the Building Code, which is the statutory test to be applied in issuing a code compliance certificate for building work that was consented under the Building Act 1991.

The Decision

The determination found that the authority incorrectly exercised its powers in refusing to issue the code compliance certificate.

Determination 2011/034: Does work to an existing building constitute ‘major alterations’, and therefore should a section 73 notice be issued in respect of land subject to natural hazards?

The determination arose from a dispute about a building consent authority’s (BCA) decision to refuse to issue a building consent unless it was subject to a notice under section 73 of the Building 2004. The BCA was of the opinion that the land on which the property is situated is subject to the natural hazard of slippage and considered that the proposed works were not “minor”. The determination therefore considered whether the authority was correct to refuse to issue the building consent.

The parties to the determination were the owner of the building, who applied for the determination, and the BCA.

Background

The building work in question related to the proposed construction of a new double garage (49m2) attached to the house, and associated earthworks. The garage was to replace a 23m2 carport.

The property on which the building work was to take place is situated on ground, that is otherwise considered ‘good ground’ in terms of NZS 3604, within the “Tahunanui Slump”. The slump is a large complex rotational landslide covering approximately 26 hectares that is still in the process of slippage in varying intensities.

The BCA had applied an approach in regards to section 73 based on a non-formal assessment of value, risk, and building area, and considered that minor work generally fell in line with schedule 1 exemptions. Because of the size and nature of the proposed building work, the authority considered that the work did not meet it’s criteria for what it would consider to be minor work.

Discussion

In order to come to a view regarding the application of section 73, the determination considered:

Section 71(3) - whether the land on which the building work was to be carried out was subject to the natural hazard of slippage under section 71(3)(e)
Section 71(1)(a) – whether the proposed building work was major alterations in terms of section 71(1)
Building Code compliance - whether the proposed building work would comply with the Building Code, including (if required) any waivers or modifications issued in terms of section 67.

Section 71(3)

The determination found that the land was subject to the natural hazard of slippage and that it was the entire site, rather than the area to be occupied by the proposed garage, that required consideration in respect of the natural hazard. Further, not enough evidence had been provided to establish that the land on which the garage was to be built would not be subject to slippage. That being the case the proposed building work needed to be considered in terms of section 71(1).

Section 71(1)(a)

Though it was noted in the determination that any building work not requiring a building consent by virtue of being exempt under Schedule 1 does not trigger the requirement to issue a section 73 notification; the determination also concluded that it does not follow that building work that is not exempt would automatically be considered ‘major’ work under section 71(1).

In order to establish whether the work is a major alteration in the context of section 71(1) in this instance the determination considered:

the degree the building work differed from that that would be exempt under schedule 1 (major work being likely to be significantly different in nature and extent)
the intended use and degree of design and construction complexity
the size of the alteration compared with that of the existing building
the increased footprint and the percentage increase in site coverage
allowance for the replacement of existing structures with new work
the extent to which the performance of the building work is likely to be affected by the hazard conditions, and whether the effects could be mitigated.

The determination evaluated these factors and came to the view that the building work could not be considered a major alteration in the context of section 71(1).

As the determination arrived at the view that the land on which the garage was to be built is subject to a natural hazard but that the work could not be considered a major alteration, it concluded that sections 71 to 73 did not apply in this instance.

Compliance with the Building Code

The determination considered there was insufficient mitigation of the effects of any future land slippage, and that the garage would not comply fully with the requirements of Building Code Clause B1 Structure. The performance requirement of Clause B1.3.1 requires that “buildings … shall have a low probability of rupture, becoming unstable … throughout their lives”.

Because the likelihood of movement of the land supporting the garage over the course of its intended life, the determination came to the view that it would be appropriate for the authority to consider a modification of Clause B1 under section 67, if one was applied for. The determination also noted that a different design could better address the requirements of Clause B1.3.1.

The Decision

The determination concluded that:

the site was subject to the natural hazard of slippage under section 71(3)
the proposed building work was not a major alteration in terms of section 71(1)
the proposed building work did not comply with Clause B1.3.1 of the Building Code and accordingly the determination confirmed the BCA’s decision to refuse issue the building consent, albeit on different grounds.

Learning curve

Barrier Free

Barrier Free NZ Trust provides education seminars, technical expertise, published material and advocacy for universally accessible built environment.

Barrier Free is made up of consumers and individuals with experience and expertise in local government, the building industry, and the disability sector.

Its education programme attracts CPD points and is essential for those working in the design and construction of public buildings. This year’s training programme is detailed below.

Barrier Free seminars

Date	Location	Duration
22-23 September	Christchurch	2 days
14-15 October	Auckland	2 days
24-25 November	Wellington	2 days

In-House 1 day training Seminars

Accessibility and Design: Access and Use of Buildings This programme content focuses on the interaction of people and the built environment; this is useful training for those involved in design, construction, management of buildings and for community organisations supporting users with disabilities who use the public spaces and places.

This seminar has been designed for those who have knowledge of the Building Act 2004 (and associated documents, regulations and standards).

To inquire about our In-House seminars please contact Lorraine on (04) 915 5848.

For architects and designers

Date	Location	Duration
12 October	Auckland	Half day

Module 5 seminar - becoming a Barrier Free Advisor (BFA)

Date	Location	Duration
2 December	Wellington	1 day

Presentations and workshops can be created to suit your individual needs.

For more information about courses call Lorraine on (04) 915 5848, or email admin@barrierfreenz.org.nz

Building Networks

Building Networks NZ Ltd specialises in building law compliance training. This year’s workshops, seminars, presentations and events are detailed in the table below.

Date	Course	Location	Duration
Wednesday, 24 August	IQP Forum 2011	Christchurch	1 day
Tuesday, 30 August	BWOF Owners and Property Managers	Rotorua	1 day
Wednesday, 31 August	BWOF Owners Checks	Rotorua	1 day
Tuesday, 1 November	BWOF Owners and Property Managers	Auckland	1 day
Wednesday, 2 November	BWOF Owners Checks	Auckland	1 day
Thursday, 3 November	Train the Trainer	Auckland	1 day
Tues - Wed, 15-16 November	IQP Checks for Means of Escape, 2 Day Workshop	Auckland	2 day
Thursday, 17 November	IQP Checks for Access for People with Disabilities and Safety Barriers	Auckland	1 day

Visit the Building Networks websiteand register online, or contact office@bnets.co.nz