Codewords Issue 53 - October 2012
Welcome to the October issue of Codewords – keeping you up to date with information from the Building and Housing Group of the Ministry of Business, Innovation and Employment.
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Section 1: Lead Articles & News
Working hard in Canterbury
MBIE’s Building and Housing staff are actively involved in several aspects of Canterbury’s recovery – whether through providing technical advice to the Royal Commission; developing technical solutions to address complex building issues; developing new policy frameworks; providing information to home-owners; or sorting out temporary accommodation. We’re here for the long haul.
Building and Housing continues to take a key role in the Canterbury rebuild, working closely with local councils and the Canterbury Earthquake Recovery Authority (CERA).
Our people on the ground
The earthquake response has required a change in the way we work, as a government agency. Some staff have moved to Christchurch, and have become Cantabrians.
We’ve been fronting up at regular public meetings, helping residents understand often complex building issues. We’re working closely with the building sector, and also with insurance companies, to help solve complex technical and policy issues on the ground.
Providing technical guidance for the rebuild
Much of Building and Housing’s work in Canterbury is technical. This includes producing technical guidance to help ensure that repairs and reconstruction work will withstand future earthquakes and will keep people safe. The three foundation technical categories – TC1, TC2 and TC3 – are part of this guidance.
A comprehensive sector education programme is under way to help practitioners apply this guidance. The training programme is designed to help the sector deliver efficient, quality repairs and rebuilds for Canterbury homeowners.
Initial training for Canterbury building consent authorities was held in August, with further training for staff scheduled for October. Project Management Offices (PMOs) are being offered monthly seminars. Workshops for engineers and architects are planned for November and December.
Making sure we have the right skills
It’s important to develop a building skills base that is up to the massive challenge of rebuilding Canterbury, and gives confidence that buildings will be repaired or built right the first time.
We are working with the private sector to achieve this, through the Building and Construction Sector Productivity Partnership.
The Restricted Building Work designation (which was introduced on 1 March 2012) and the Licensed Building Practitioners’ scheme are also key initiatives which support a quality rebuild.
Supporting the Royal Commission with technical advice
Building and Housing has provided expert technical advice to the Canterbury Earthquakes Royal Commission of Inquiry, which recently held hearings into the performance of central city buildings, including the CTV building.
The findings of the Royal Commission, along with Building and Housing’s recent technical investigation into the structural performance of key Christchurch CBD buildings, will inform future building design and construction. This significant work will underpin changes to the Building Act, the Building Code and also professional standards - and will ensure New Zealand learns from the earthquakes.
Building and Housing’s review of the Building Act’s earthquake-prone building policy provisions and provisions will help the Government respond to the recommendations of the Royal Commission - and will help local government and the sector to implement the Commission’s recommendations.
Finding temporary housing for people
The need for temporary housing has been a significant issue in Canterbury. Building and Housing is part of a joint venture with the Ministry of Social Development to help people whose homes were badly damaged by the earthquakes.
This joint venture, called the Canterbury Earthquake Temporary Accommodation Service (CETAS), works with people to assess and match their housing needs with the accommodation market. This includes private sector providers and temporary villages.
The villages, in Linwood, Kaiapoi and Rawhiti (New Brighton), supplement the private sector and provide temporary accommodation for people while their earthquake-damaged homes are repaired or rebuilt.
Here for the long haul
Building and Housing has been at the fore in many areas, helping residents and businesses in Christchurch and Canterbury recover from the earthquakes and look ahead to the future. The Canterbury rebuild is a priority for MBIE, and we will continue to have an active role in Canterbury for many years to come.
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'Grand Designs' comes to Christchurch
Design professionals and property developers are invited to enter an exciting design competition for a housing development to be built in central Christchurch.
Christchurch City Council and the Ministry of Business, Innovation and Employment are collaborating on the Housing Showcase Design Competition launched on 15 October.
This competition is part of ‘Breathe – The new urban village project’.
The competition is an opportunity for any consortium that includes a design professional and property developer, to design a medium-density housing development, showcasing inner city living options in the central city. Stage 1 of the competition is seeking innovative and exciting concept designs that are able to be translated into an inner city housing complex.
In February 2013, three of these designs will be chosen to develop their concepts to progress to Stage 2, and will be awarded $20,000 to complete that work.
The selected site is in the heart of the city, next to the proposed new ‘Green Frame’ and opposite the north end of Latimer Square.
The competition is about finding a design that is able to contribute to a bold and visionary rebuild of Christchurch’s central city. Having ‘Grand Designs’ host Kevin McCloud as a member of the judging panel highlights the international importance of the project in helping shape inner city housing all over the world.
The competition winner will be announced in August 2013, with construction due to commence in December 2013.
One of the competition’s aims is to launch the early redevelopment of the inner city, providing an exemplar for further housing developments. Residents living in the new complex ‘will help bring life back to Christchurch’s central city and lend a new vibrancy to support the city’s regeneration’. (Breathe – The new urban village project)
You can read more about the Central City Plan at the website below.
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This edition outlines a change in role for David Kelly and Alison Geddes, and introduces Adrian Regnault as the Acting Deputy Chief Executive of MBIE’s Building Quality Branch.
There have been a few changes in the senior team at Building and Housing since our last issue of Codewords.
David Kelly, formerly the Deputy Chief Executive (DCE) of the Building Quality branch, recently moved into a newly-created MBIE role as Director, Canterbury Rebuild and Recovery. His new role, leading Ministry-wide support for the Canterbury rebuild, encompasses Science and Innovation, Labour, Economic Development and Building and Housing activities. Dave will work closely with the Canterbury Earthquake Recovery Authority (CERA) and industry organisations to support the rebuild and ensure the programme benefits all of New Zealand in the longer term.
Adrian Regnault, previously the manager of construction policy in the Sector Policy Branch, has moved into Dave’s previous role and is now the acting Deputy Chief Executive of Building Quality. Adrian is focused on earthquake recovery priorities, and particularly on implementing the systems needed within the Branch to develop efficient, high-quality technical solutions for the Canterbury rebuild. Going forward, actioning the findings of the Canterbury Earthquakes Royal Commission will be a high priority, along with incorporating key learnings from the earthquakes into New Zealand’s Building Code system.
Alison Geddes recently crossed the Tasman to take up a senior role with the Parramatta City Council in Sydney. Alison joined us two years ago as Deputy Chief Executive, Sector Capability - after 10 years in planning and building sector management roles at the Auckland City and North Shore councils. We wish Alison every success in her new role.
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This article briefly outlines progress with finalising the new Ministry’s structure.
The high-level structure for the new Ministry of Business, Innovation and Employment (MBIE) was confirmed on 31 July 2012, and the detailed design structure was confirmed on 17 October.
MBIE will have eight groups – two corporate and governance, three policy-related (including Building and Housing functions) and three for service delivery/operations. Announcements are being made this month for each new Deputy Chief Executive (DCE).
Staff in the (current) Building and Housing, Science and Innovation, Economic Development and Labour Groups will start migrating to the new structure later this month.
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Section 2: Technical Update
Lap lengths for reinforcing steel mesh fabric
This article advises how to make sure that sheets of reinforcing steel mesh are properly lapped to prevent a crack from forming and the slab (or other concrete member) from failing, at the lap joints.
Following the series of Canterbury earthquakes and the damage to concrete-slabs-on-ground, measures were introduced to the Building Code’s supporting document B1/AS1, to increase the resilience of concrete slabs on good ground against earthquake shaking. One of these measures was the requirement for Grade 500E reinforcing mesh fabric (see the previous issue of Codewords).
Reinforcing steel mesh fabric is used (with and without other reinforcing steel) in concrete members such as floor slabs and walls. It resists forces and displacements induced by gravity loads, earthquake shaking, ground movement and shrinkage strains. Reinforcing steel mesh fabric is made from wires that are welded together to form sheets.
To ensure good performance, it is necessary to make sure that the sheets of reinforcing mesh are properly lapped to prevent a crack from forming and the slab (or other concrete member) from failing at the lap joints.
Laps need to be able to develop more than the elastic yield strength of the reinforcement, otherwise sudden failure can occur at the lap.
This may be achieved either by following the Building Code supporting documents, or by an alternative solution proposal.
Building Code supporting document methods
All reinforcement must meet the requirements of steel reinforcing standard AS/NZS 4671:2001.
Verification Method B1/VM1
The Verification Method B1/VM1 cites the Concrete Structures (Design) Standard NZS 3101:2006 which provides two methods for determining the lap length. Both methods will produce a lap that is at least as strong as the characteristic elastic yield strength of the longitudinal wire that is being lapped.
Using two cross wires for anchorage: Clause 8.7.6(a) of NZS 3101:2006 requires a lap of one mesh space plus 50mm. The minimum is 150mm for plain round wire mesh. This relies on a cross wire weld developing in shear half the elastic yield strength of the largest mesh wire at the joint. This method may be used for both plain and deformed wire mesh. The Building and Housing Group’s guidance on reinforcing mesh is based on this method.
Straight lapping of mesh wires: This method can only be used to lap deformed wire mesh. The Building and Housing Group’s guidance on reinforcing mesh specifies a lap length of 40 deformed wire diameters. A more optimal lap length may be calculated from NZS 3101. See Clause 8.7.6(b).
NZS 3101 does allow anchorage of plain round wire using hooks or bends (Clause 8.6.4) or mechanical anchorage (Clause 8.6.11). However, these methods are normally not practical or economic.
Acceptable Solution B1/AS1
This modifies NZS 3604:2011 by requiring a lap of 225mm, or the welded wire manufacturer’s requirements – whichever is greater.
Alternative solution proposal methods
Lap lengths can be varied from the above, if sufficient testing is carried out.
Testing must include lap length tests and cross bar weld strength tests, and must specify all the relevant test parameters, such as the minimum 28-day concrete compressive strength and wire mesh fabric properties (verified as meeting or exceeding AS/NZS 4671).
The assessment should also look at the potential impact on concrete crack formation at high stress levels. In other words, even if the lap length test performance is adequate, additional lap length allowance is still required, to limit crack formation resulting from the loss of reinforcement bond.
Such testing and assessment should be accompanied by a technical opinion from a building professional such as a chartered professional structural engineer.
For these Alternative Solutions, the information should be presented in such a way that building control officials can easily see how side and end laps are made, and that the basis for them is different from those laps specified in the Building Code supporting documents.
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Concrete tile roofs amendment
In August 2011, E2/AS1 was amended to accommodate an increase in ‘design wind speed’ and ‘design wind pressure’. This article describes how these amendments affect concrete tile roof underlays and underlay support.
In August 2011, amendment 5 to E2/AS1 was published. This included several changes to accommodate an increase in the maximum design wind speed.
This change aligned E2/AS1 with the increased wind speeds in NZS 3604:2011 (Timber-framed buildings), increasing the maximum design wind speed by 10 percent, and design wind pressure by 20 percent.
These are significant increases. They resulted in the creation of a new wind category of Extra High (EH) for design wind speeds above 50m/s, but not exceeding 55m/s.
Most detailed information throughout E2/AS1 remained unchanged for wind categories up to Very High (VH). However, some special wall and roof cladding requirements were added for cladding materials and installations in the EH wind category.
The amendment affects concrete tile roof underlays and underlay support.
Concrete tile underlays
The majority of roof installations are Type I (double pan) tiles on roofs steeper than 20 degrees, for buildings with Low, Medium or High site wind speeds.
These do not require roof underlays.
However, the tile manufacturer’s literature may recommend the inclusion of underlays as good practice, regardless of E2/AS1 minimum requirements.
Note that roof underlays are required for all concrete tile roofs in sites with Very High and Extra High wind conditions, irrespective of roof pitch. This is a new requirement in Amendment 5.
All Type II (single pan) tiles and Type III (flat profile) tiles require roof underlays, irrespective of roof pitch or site wind speed. This is unchanged from the previous amendment. (Refer to E2/AS1 paragraph 8.1.5 for roof underlay type and installation details.)
Roof underlay support
Type R1 underlays require full support, including anti-ponding boards. (Refer to E2/AS1 paragraph 184.108.40.206 for underlay support and paragraph 8.2.5 for anti-ponding boards.)
Type R2 self-supporting roof underlays do not require support. Although E2/AS1 makes no distinction about the type of underlay and the use of anti-ponding boards, Type R2 self-supporting underlays, if well installed by being pulled taut over the fascia and secured prior to installation of first tiles, will achieve drainage without anti-ponding boards.
Homeowners (or their designers), choosing underlays that exceed the minimum requirements of E2/AS1 are not bound by the details in E2/AS1, and your specific manufacturer’s installation details may provide discretion over the use of anti-ponding boards in those situations.
However, it is highly recommended that for concrete tile roofs below 17 degrees, anti-ponding boards should always be used.
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New Standard for platform lifts
Standards New Zealand has developed a platform lift Standard, in close consultation with Building and Housing. Find out about the new Standard (NZS 4334: 2012 ‘Platform lifts and low-speed lifts’) and when to use it.
Platform lifts are used in homes, and in small public buildings (up to a few storeys high) where the Building Act requires an accessible route. The lifts are low-speed, low-rise lifts, primarily used by people with reduced mobility.
In public buildings, platform lifts are not expected to carry the majority of the building’s traffic.
Existing Standards didn’t suit platform lifts
Platform lift installation comes under the Building Act and the Building Code. Clause D2 of the Building Code is particularly relevant, as it covers ‘Mechanical installations for access’.
Although the performance requirements of Clause D2 apply to platform lifts, there is no suitable Acceptable Solution:
- Acceptable Solution D2/AS1 cites NZS 4332 ‘Non-domestic passenger and goods lifts’ and EN 81 (the equivalent European Standard). However, these Standards are for high-rise lifts, and their provisions are excessive for platform lifts.
- Acceptable Solution D2/AS2 cites the 1985 ‘Rules for power lifts not exceeding 750 watts (one horsepower)’. However, methods of constructing modern platform lifts have moved on since then.
So a new Standard has been created
In close consultation with the (then) Department of Building and Housing, Standards New Zealand has developed a new platform lift Standard: NZS 4334: 2012 ‘Platform lifts and low-speed lifts’.
The Standard has been designed for homes, and for small public buildings (up to a few storeys high) where the Building Act requires an accessible route. The Standard describes the use of ‘platform’ and ‘low-speed’ lifts within well-defined limits.
When used within those limits, the Standard provides for practical lifts, without all the features of a high-rise lift. The new Standard enables Code compliance, in that it provides for the safe and easy movement of building users.
A platform lift has a maximum speed of 0.15 m/s. Depending on its degree of enclosure, it can have a travel distance of up to 7.5 metres.
A low-speed lift, which has greater enclosure than a platform lift, can have a maximum travel distance of 15 metres with a maximum speed of 0.3 m/s.
The Standard retains the 1400 x 1400 mm car platform size for lifts in public buildings. It does, however, allow an 1100 x 1400 mm platform in certain situations where only two levels are served.
The new Standard has been developed so it can be cited in an Acceptable Solution for D2, as a replacement to the outdated 1985 Rules. Consultation by MBIE is yet to take place. In the meantime, practitioners are encouraged to use the new Standard (NZS 4334) as a means of constructing lift installations that are compliant with the Building Code.
For more information, or to purchase the Standard, visit the Standards New Zealand website.
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Section 3: Learning Curve
Codewords likes to keep you up to date with building and construction courses and workshops.
Barrier Free Trust seminars
Seminars on designing accessible buildings are being provided in November 2012 by the Barrier Free Trust.
The Barrier Free New Zealand Trust offers advice, support and training to help ensure buildings and built environments are accessible to everyone, including people with disabilities.
The Barrier Free Trust holds seminars and training modules on designing and creating accessible buildings.
Some of their longer seminars can earn you Skills Maintenance points as a Licensed Building Practitioner (LBP).
- 9 November: (Auckland) Half-day seminar for architects and designers.
- 19 November: (Wellington) Seminar on designing accessible buildings.
For more about these courses or the Trust, see their website.
BOINZ: Building Control courses and materials
The Training Academy, the training arm of the Building Officials Institute of New Zealand (BOINZ), provides building control courses and materials to its members and stakeholders within the built sector.
Its training programme delivers courses to meet Unit Standard requirements within the Diploma of Building Control Surveying as well as a suite of CPD upskilling programmes ensuring members have current industry competency.
Building Networks events
Building Networks delivers training solutions for people in the building and property industries.
For details of coming events, visit:
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