Please click on a link to find out more about our past research programme:

Energy
Update of ALF3 (passive solar design guide for houses)
Household Energy End-Use Project (HEEP)
Solar water heating systems

Environment
Easy guide to helping Kiwi builders run a sustainable and profitable business
Adapting buildings to the impacts of climate change
Waste - REBRI
Compendium and evaluation of building environmental impact schemes being used in Australasia
Water end use and efficiency of use

Structural engineering
Dry bedding of veneer ties
Seismic performance of whole houses
Seismic design of high-level storage racking systems
Seismic performance of building parts
Repair of earthquake damaged houses

Fire
Reaction to fire properties of wall/ceiling lining finishes and building components
Reaction to fire properties of wall/ceiling linings
Fire loss reduction in industrial buildings: risk cost benefit study
Flame barriers for foamed plastics
Post-earthquake performance of passive fire protection systems
Human behaviour in fire
Vertical channel test
Domestic sprinklers

Materials
Plastics weathering
New carbonation cements
Timber preservative corrosion effects
Influence of timber treatment preservatives on resistance-based moisture meter readings
Concrete durability
Indicator materials
Reactive powder concretes
House condition survey

Other
The future of housing in New Zealand
Soil expansivity in Auckland
Flanking noise

Energy

• A web basis so the calculation tool is accessible to all of the industry. This will overcome one of the main limitations of the current software, namely that it is platform dependent and Apple Mac users need to purchase and install Windows emulation software. A web-based approach will also allow more rapid upgrades and user customisation.
• A new module for residential ventilation design that accounts for infiltration, passive vents and small mechanical systems such as range hoods and bathroom ventilators. This offers a performance basis and verification method for residential passive ventilation in clause G4 of the NZBC.
• A new module to assess condensation risk in houses and compliance with clause E3 of the NZBC. This provides a set of the variables (insulation, solar access, purchased heat, New Zealand climate and ventilation) that are consistent with moisture and mould mitigation in homes. 

This should  assist the industry to design residential buildings to meet ventilation standards using passive methods, and to meet the indoor moisture control requirements of clause E3, and to test novel building designs against the performance clauses for energy efficiency, ventilation and indoor moisture management. More about ALF

Household Energy End-Use Project (HEEP)
This project is the most thorough investigation of the way that energy is used in New Zealand homes since the 1970s. The project commenced in 1995 with a pilot study and progressed to detailed data collection in four hundred houses from throughout New Zealand. The sample includes households from large and small cities, urban and rural areas and both the North and South Islands. HEEP monitoring activities include a detailed occupant survey as well as a detailed house energy examination. The monitoring covers all fuel types (electricity, natural gas, LPG, solid fuel, solar water heaters) as well as temperatures in at least three locations.

The Household Energy End-Use Project (HEEP) had as its objective to measure and model the way energy is used in New Zealand households. The project was funded continuously by the Building Research Levy and at various times in various ratios by FRST, EECA and others.

The finally-developed database relates physical building and appliance characteristics as well as socio-demographic factors to describe the energy consumption patterns and some of the energy services, in particular, the achieved indoor temperatures. The model has already had an impact on national energy policy and will continue to be be used to understand national household energy requirements and as a tool to evaluate the implications of building and appliance performance changes.

Description of the methodology used:

Data on summer temperatures in NZ houses:

The way solid fuel heating is used:

Hot water usage in New Zealand houses:

Baseload and 'standby' electricity demands:

More about HEEP

Solar water heating systems
BRANZ produced a report in late 2005 that reviewed likely cost benefit analyses of solar water heating systems in New Zealand, and whether world-best systems were available in New Zealand. The work concluded that payback periods varied between eight and twenty years depending on circumstances, and that the available systems were appropriate. Download a copy of the report

BRANZ identified that one of the biggest uncertainties in the cost benefit analysis of solar water heating systems is the lack of reliable field data for system performances. Anecdotal evidence suggests that most existing systems fall significantly short of the calculated values used during the system design. They suggested that this information gap needs to be urgently addressed by conducting a representative field study of existing solar water systems in New Zealand.

Further work, funded by EECA and the Building Research Levy, examined installations in Auckland, Wellington, Christchurch and Dunedin, and monitoring their actual performance. There was an early report on materials performance and installation issues.

The performance assessment was scheduled to take an extended period to allow for review of seasonal effects, and the full report on 36 installations in Auckland, Wellington, Christchurch and Dunedin on this is now available.

Key issues are the angle at which the collector is installed to ensure that there is the optimum year-round energy collection, and the need to ensure that householders know how to ‘run' the system to get the best from it. An executive summary, and EECA's commentary on the changes in the solar water heating sector since the testing began, can be found here.

Environment

Easy guide to helping Kiwi builders run a sustainable and profitable business
The Building Act 2004 introduces a concept not covered by the previous Act - that "buildings are [to be) designed, constructed and able to be used in ways that promote sustainable development".

BRANZ provided a set of tools for the industry to address this in terms of planning and actions for site work. The Easy Guide - now known as the Sustainable Foundations Programme - was launched at the 2006 conference of Registered Master Builders in Queenstown, and contains a set of steps to help those in the industry understand environmental profiling (the business's environmental, social and financial footprint, and consequent responsibilities and opportunities), under these headings:

• Write your environmental policy
• Put an environmental management system in place
• Reporting.

The toolkit was trialled on several building sites before final publication, and delivers practical, tested advice on the best approach.

Adapting buildings to the impacts of climate change
BRANZ has compiled a consolidated understanding of the impacts of climate change on New Zealand's built environment. This should assist better decision-making at commissioning and design stages to ensure the building stock is better prepared for these impacts in the short, medium and long-term.

The work examined how the current built stock is placed to deal with latest predictions of climate change impacts for New Zealand through the 21st century. It foresees significant rises in risks related to coastal flooding, erosion and rising water tables, inland flooding, overheating due to solar gain, and forest/bush fire, with consequent potential rises in insurance costs. There may be opportunities for decreased water heating and winter space heating costs. Social impacts of climate change may include social disruption and conflict over changing patterns in the value of land in coastal areas, and inefficiencies in the housing stock if an ageing population increasingly remain in their own homes.

The report advances a Climate Change Sustainability Index (derived in a previous FRST-funded research project) as a tool to assess building climate change vulnerability.

Waste - REBRI
Waste has both environmental and financial costs. Work continues on examining the potential for the reuse/recycling of waste materials. With the New Zealand Waste Strategy now available, an understanding of where effort can be best directed is emerging. Further, the Ministry for the Environment is able to apply resources from the Sustainable Management Fund to the direction provided by the Strategy.

BRANZ has co-operated with nine Territorial Authorities and the Recycling Operators of NZ Inc (RONZ) to develop a comprehensive set of measures aimed at reducing waste in the building and construction sector. Educational, legislative and practical support documentation for seven industry sectors has been provided as part of this programme. Substantial support for this project was also provided from the Ministry for the Environment's Sustainable Management Fund. Visit the REBRI website.

Compendium and evaluation of building environmental impact schemes being used in Australasia
A building environmental impact scheme is a tool for evaluating the environmental design or operational performance of a building. There are many schemes currently available with many more under development. While there are commonalities between the schemes, no two are exactly the same. For the building and construction industry and other urban practitioners, knowing which scheme to use can be a challenge, especially if the intent of the scheme is unclear.

This report identified the major schemes in use in Australasia (including those in their pilot stages or under development) in mid-2005. It provides an expert opinion on which schemes may be the most appropriate for use as the primary scheme in New Zealand. The report notes that the decision-making process about which building environmental impact scheme to use will continually evolve and that for any scheme to remain successful will require it to be continuously supported and updated.

Water end use and efficiency of use
The Building Act 2004 placed emphasis on sustainability issues, and one specific focus was water efficiency. Water use is already a significant issue at present in many parts of New Zealand, yet there appears to be no reliable data on how water is used in New Zealand households. The Building Research Levy funded BRANZ to develop a robust methodology for monitoring end uses of water in residential homes, which would be available for use by a number of parties (e.g. regional councils, Ministry for the Environment, Territorial Authorities and water companies) for their specific interest projects.

An initial literature review on the subject:

The report on the pilot study of 10-12 houses, including both low and mains pressure water systems, in the Kapiti Coast area:

Structural engineering

Dry bedding of veneer ties
It is common industry practice to ‘dry bed' ties - to lay the tie on the brick or block and run the mortar layer over the top of it. This is not in compliance with the standard AS/NZS 2699.1. A research programme devised in association with the Master Masonry Trades Federation explored the use of ties with the various available veneer blocks and has found that dry bedded ties could achieve the performance requirements stated in AS/NZS 2699.1:2000, but that care needed to be taken to ensure that concrete blocks were adequately moistened before use.

Seismic performance of whole houses
Houses that are designed in accordance with the Timber Framed Buildings Standard, NZS 3604, typically require a number of bracing elements to resist lateral seismic loads. Isolated building elements are tested in the laboratory to get a bracing rating using the test method nominated in NZS 3604 - the BRANZ P21 method. Recent research undertaken indicates a poor correlation between laboratory testing of individual elements and in-service performance of complete houses.

The contribution of non-structural elements, through either secondary bracing or damping effects, is not well understood and cannot be assessed through modelling, and as house forms become more complex, they pose further problems for structural engineers designing lateral bracing elements. BRANZ was commissioned to investigate the issue of whole house seismic performance and develop a technical basis for contributions towards revising either existing standards or NZBC Approved Documents.

A particular finding was that load paths from the roof to the ground need to be carefully built when very strong bracing panels are involved in the construction. Three reports were produced, addressing the desirable upper limit wall bracing strength to ensure assumptions about available load paths are met in NZS3604 construction, based on theory and on laboratory studies.

Foundations:

Single-storey construction:

Two-storey construction:

Seismic design of high level storage racking systems
Tall, heavily loaded racking systems are a common feature in retail outlets such as supermarkets. Several instances of the collapse of such shelving systems in the Northridge earthquake in the USA in 1994 were testimony to the severe hazard posed by such systems in earthquakes. A number of features of racking make these systems vulnerable to collapse in an earthquake - they are made from light gauge steel, they are heavily loaded, heavy product is stored at the top of the shelving, lateral bracing is often not symmetric, base fixings are light duty and so on. BRANZ developed design recommendations on this with funding from the Building Research Levy, the Department of Building and Housing and the Earthquake Commission.

Seismic performance of building parts
A number of items in a building are either attached to or supported by the primary structure of the building - such items are often referred to as ‘parts'. If design is handled ineffectively, significant damage can occur to non-structural parts of a building in relatively minor earthquakes. Typical non-structural components would be architectural partitions, piping systems, electrical and mechanical systems and so on, which, in a nonresidential building, would often represent over 50 percent of the building cost.

The earthquake actions section of the joint Loadings Standard, AS/NZS 1170.5 (Part 5) superseded the comparable section of the existing New Zealand Loadings Standard, NZS 4203. Development of Part 5 of the new standard, in relation to dealing with building parts, has drawn heavily on research funded by the Building Research Levy. The knowledge required to design for the earthquake actions on parts of buildings is generally outside the expertise of ‘parts' manufacturers in New Zealand, and the issue is often overlooked by designers. In response to this need, prescriptive guidance was provided in Part 5 of the new Standard. This information drew heavily upon research conducted by the National Earthquake Hazard Reduction Programme in the USA. The technical basis for this American data is not understood in a New Zealand context, and in many instances, the data appears to be suspect. Research by BRANZ has developed an evaluation method relevant to New Zealand.

Repair of earthquake damaged houses
Work by BRANZ, jointily funded by the Building Research Levy and EQC, has reviewed repair procedures for dwellings built before the advent of NZS 3604, to ensure that the repaired elements have adequate performance in future events. In the laboratory, they replicated damage sustained in earthquakes and examined repair procedures for stucco wall claddings, softboard ceiling linings, hardboard ceiling linings, and lath and plaster walls. Re-levelling structures using a ground injection technique was also investigated The damage and repairs have been summarised, along with suggested other considerations, so that they may be incorporated into the Earthquake Commission's Earthquake Damage Assessment Catalogue.

Fire engineering

Reaction to fire properties of wall/ceiling linings
It is necessary to control the fire properties of building products to ensure that the rate of flame spread and smoke production involving floors, walls and ceilings is limited to an extent commensurate with the ability of building occupants to safely evacuate the building. There have been many instances of fire spread by ignition and transmission by ceiling, wall and floor coverings, and there are question marks over the appropriateness of the tests specified for them. The Building Research Levy, the Department of Building and Housing and Plastics NZ co-funded research by BRANZ to define a clearer basis for assessing the fire hazard of such materials. The project is expected to assist industry by delivering a more realistic test regime and the Department of Building and Housing in their intended development of quantifiable performance criteria for inclusion in the Compliance Document and the New Zealand Building Code. The report recommends that materials that reach flashover in less than 120 seconds when exposed to a 100 kw source in a test to ISO 9705 should be forbidden from use as wall and ceiling linings in all buildings, and makes other recommendations for changes to the fire test methods in NZBC Compliance Documents.

Fire loss reduction in industrial buildings: risk cost benefit study
A BRANZ project co-funded by the Building Research Levy and the NZ Fire Service has investigated the cost-effectiveness of different fire protection strategies for use in industrial buildings in New Zealand and developed a risk cost benefit model to estimate the cost of fire in industrial buildings. Based on the upper 95 percent confidence level for the expected cost of fire per building per year, it concluded that no change to the fire protection system requirements in the New Zealand Building Code Compliance Documents for industrial buildings is warranted. However, for buildings of more than 1,000 m² in floor area, automatic fire detection with manual suppression is recommended as the preferred option, closely followed by fire sprinklers. You can obtain the report here. 

Flame barriers for foamed plastics
The current Approved Document for the New Zealand Building Code Fire Safety Clauses requires that all foamed plastics building materials be protected by a flame barrier that will delay the involvement of combustible foamed plastics in a fire, slowing the internal spread of fire and production of smoke in buildings. Previous research had suggested that the existing requirements of the Acceptable Solution were placing too much reliance on the subjective judgement of the test laboratory and more robust test and performance criteria were needed.

This study was co-funded by the Building Research Levy and the Department of Building and Housing (DBH). It demonstrated the effectiveness of the ISO 9705 room corner fire test method in evaluating the reaction to fire performance of polystyrene insulated panels (PIP) and differentiating the influence of various construction details used to join the panels on that fire performance. The results of the measurement of heat release rate (HRR) and smoke production rate (SPR) are a direct indicator of the opening (failure) of panel joints that expose the foam core to fire, allowing the escaping volatiles to contribute to the HRR and SPR. The recorded increases in the HRR and SPR were shown to be directly related to the opening of the panel joints, which, in turn, was dependent on the jointing detail, so the stability of the construction details when subjected to fire exposure was demonstrated by the ISO 9705 test method to have a direct relationship to the fire performance achieved.

Post-earthquake performance of passive fire protection systems
Passive and active fire protection systems play an important role in achieving the fire safety performance requirements of the NZ Building Code. Passive fire protection systems are required to reach minimum standards of performance when subjected to standard fire resistance test conditions. It was anticipated at the time the research was commissioned from BRANZ that, following earthquakes of even moderate intensity, there is a reasonable likelihood that a number of passive fire protection systems will be damaged to such an extent that they will not be able to provide the level of fire resistance that they are designed to achieve. The economic benefit of research in this area would be a reduction in fire damage to buildings and social benefits resulting from improved levels of life safety.

The research showed that the post-earthquake performance of passive fire protection systems is definitely reduced when subjected to a design level earthquake. The amount of reduction in fire resistance of a 60 minute plasterboard lined wall can be as much as 50 percent. This is of increased importance considering that active fire protection systems such as sprinklers may have also been rendered inoperable in the earthquake event, with the problem potentially further compounded by the increased likelihood of fire outbreak due to disruption of building activities and services, and consequent serious life safety issues for building occupants.

Vertical channel test
This long-running project to further develop and validate an alternative fire test method for flame spread up combustible building facades has resulted in BRANZ Study Report 137:

and Technical Recommendation 16:

Domestic sprinklers
This project set out to provide the plumbing industry and the wider building industry with information that will enable better decision making when designing sprinkler systems that are part of the potable water supply and provide architects, designers and fire engineers with the basis for an Alternative Solution (to NZ Building Code requirements) that includes combination sprinkler systems. Testing of effects on water quality suggested there is no problem with ‘dead legs' up to 3 metres long. Because of the lack of features such as flow switches and interconnected alarms required by various standards, domestic sprinklers are likely to be less reliable in fighting fires than fully commercial systems, but with some enhancement, such systems may be useful in situations which do not, by regulation, need sprinklers, but would benefit from them, such as in multi-residential buildings.

An output of this work was the sprinkler design guide:

Additional work was undertaken to quantify the "dead leg" safety of such systems:

Materials

BRANZ-funded research into the natural weathering of a number of building plastics at four exposure sites around the country has shown that there are significant differences in the rates of photodegradation of polymeric materials at the different exposure sites. This work will be extended to incorporate more plastic and polymer types, and will involve additional sites around the country. The development of a New Zealand weathering indices map and degradation study for various plastics will be beneficial in acquiring and passing on information on the durability of building polymers within various environments. This research is part of a series of research projects to determine the lifetime of polymeric materials within specific environments.

The work showed that mild steel corrosion rates in contact with timber treated with CuAz or ACQ can increase markedly at the H3.2 hazard level relative to the equivalent CCA-treated timber, with a much higher corrosion rate at the ACQ H5 hazard level. The corrosion resistance of hot-dipped galvanised materials was also significantly reduced in ACQ-treated timbers. 316 stainless steel performed very well in all of the preservative treatments examined.

Influence of timber treatment preservatives on resistance-based moisture meter readings
BRANZ has examined the results given by three conductivity-based moisture meters for moisture content of treated and untreated Pinus radiata specimens, after the timber had been conditioned at 65 percent, 75 percent or 98 percent relative humidity, using a standard oven-dry method for calibration of the actual timber moisture contents. The treatments included boron, LOSP, CCA and ACQ. The manufacturer-supplied correction tables worked well for untreated timber, but the presence of treatment lowered the accuracy of all of the meters in a way dependent on the timber preservative type and the mode of meter operation. The work suggested that there is no possibility of issuing a single set of correction tables that will work with every brand of commercial moisture meter.

Concrete durability
In the last decade, the use of supplementary cementitious materials (SCMs, also known as blended cements) in New Zealand has become widespread in situations where there are special durability demands on concrete. Such situations often include coastal marine reinforced concrete structures. Overseas, SCM concretes are also used in industrial situations. The porosity of blended cements is reduced due to secondary reactions of the calcium hydroxide formed in Portland cement hydration. The use of SCMs means that less Portland cement is used, reducing the amount of CO₂ released into the atmosphere.

This study is a combination of accelerated laboratory tests and natural exposure of SCM concrete blocks to marine conditions, concerned principally with chloride penetration into the concrete, since it is chloride that reacts with the reinforcing steel to cause concrete spalling and cracking.

A series of concrete blocks, made from cement blended with slag, silica fume or natural silica pozzolan SCMs, were placed on exposure sites corresponding to the C, B2 and B1 exposure classification categories in NZS 3101 Concrete structures. At periodic intervals over five years, the chloride ingress profile for each combination of cement type and exposure severity was measured. This data was used to calculate notional surface chloride concentrations and effective diffusion coefficients sufficient to capture the performance of each concrete as input parameters for Fick's law-derived service-life prediction models. Statistically significant time-dependent reductions in chloride resistance were recorded for some of the blended cements. Current implementations of service-life prediction models were also critically evaluated, and the use of early-age laboratory tests for characterising durability performance was investigated.

Indicator materials
There is potential for passive indicator, or ‘tell-tale', marking technologies that can be applied to building materials during the manufacturing process. These marks would respond to environmental exposure in a way that would allow building inspectors and product manufacturers to determine if areas of the building had been closed in within the prescribed period. BRANZ explored further the opportunities for this, including understanding of existing technologies and potential barriers on the pathway to use.

Reactive powder concretes
Reactive powder concrete (RPC) has the potential to overcome low flexural strengths in concrete that necessitate auxiliary reinforcement and large sections (and thus increase aggregate use), while producing a potentially very durable product.

The feasibility of producing high strength reactive powder concrete (RPC) with domestically available materials was examined in small-scale laboratory trials with variables of water-to-binder ratio, super-plasticiser dosage, curing regime and choice of silica pozzolan.

Compressive strengths in excess of 200 MPa and flexural strength of 15-20 MPa were routinely achieved using conventional concrete mixing and curing practices. The mechanical properties of the hardened RPC depended on the efficiency with which the dry powder constituents could be packed together, and this meant that these powders needed to exist in distinct size classes with a wide separation between mean particle size diameters. This places a reliance on imported silica fume as an essential component of RPC. The benefits conferred by the fume's extremely fine sub-micron particles and spherical shape are such that substitution by indigenous geothermal silica pozzolan proved impractical.

House condition survey
The 2005 House Condition survey was carried out by BRANZ and funded by the Building Research Levy.

The findings from inspections of a total of 565 owner-occupied houses in Greater Auckland, Greater Wellington and Greater Christchurch are delivered in the report. The houses selected for the survey are matched by their decade of original construction to a broad profile of the whole national building stock.

The physical condition surveys are complemented by interviews with the house occupants. In general, occupants are less aware of defects in houses than they should be, which may contribute to an underinvestment in desirable maintenance.

This study is the third in a time series. The Building Research Levy funded a survey of the physical condition of New Zealand houses in 1994, and a second survey including both physical condition and householder demographic information in 1999.

The overall average condition of the houses surveyed in 2005 has improved by about 10 percent over the condition found in 1999, and this is reflected in a lower cost (around $3,700 per house, on average) of outstanding essential repairs. The condition overall of the stock had improved slightly between 1994 and 1999, but this was counteracted by the condition of some components becoming more costly to repair. The average cost of outstanding maintenance per house in 1999 was $4,000, with only about $1,500 per house per year being spent across the then 1.4 million houses comprising the New Zealand national housing stock.

The 2005 survey found a significant frequency of poor subfloor ventilation, poor or missing subfloor fasteners, poor ventilation of kitchens and bathrooms, lack of restraints on header tanks and hot water cylinders, and decks with unsafe barriers. Many of these were found in the earlier surveys, too - physical defects found in 1999 were deficiencies in subfloor ventilation, claddings, foundations, hot water cylinder restraints, guttering and windows.

The Building Research Levy invested in these studies to ensure that there is a clear understanding of the issues that may be affecting the suitability of the houses in which New Zealanders live. The 2005 study has expanded the previous work by:

• generating additional information to add accuracy to life cycle analyses (used in environmental impact assessments)
• strengthening the analyses of demographic data and their causative links to house maintenance
• assessing the current degree of energy efficiency measures present in the existing housing stock and thus assess the implications in bringing the stock up to standard for the NEECS
• assessing the degree of usage of unflued gas heaters, and dehumidifiers.

Other 

The future of housing in New Zealand
What will be the characteristics of our residential built environment in 2030? The Building Research Levy and CHRANZ funded a project carried out by Scion and BRANZ that addressed these issues. The full report, available here, tells five plausible stories, or scenarios, about how people might be living in their homes. A summary of the report is available here.

The Sunrise, Sunset scenario looks at regional economics. Many New Zealanders assume that housing is a ‘safe' investment, but is this defensible in all cases? In this scenario, the impact of an unforeseen regional economic decline on house/land prices and regional demographics contrasts sharply with the same issues in a nearby city, where an economic upswing brings enhanced population growth with extra pressure on infrastructure and the environment.

The Change of Heart scenario is a story about deferred nurturers with student debt who have bought a ‘disposable home' on leased land. Many New Zealanders assume that their houses will last forever. When combined with land shortages, and an emergent debt-tolerant generation that does not value ownership as highly as life experience, new paradigms of home ownership may emerge. This scenario reflects discussions about home ownership aspirations, housing affordability, attitude to debt and the durability and economic lifetime of buildings.

The Vertical Village scenario depicts life in a multi-unit multi-storey complex in the central city with better access to work. Although land in the city is scarce, the sheer impossibility of getting to work from some suburbs creates the economic conditions in which attractive high-rise communities exist in the city centre.

The Gates of Heaven scenario considers rising conservatism, a strengthened influence of Christian fundamentalist values, and changes in demographic trends. It portrays life in a gated ‘safe' community where people share the same religious values. Can such communities exist comfortably in New Zealand where many types of social segregation are frowned upon?

The Reference scenario presents an alternative outlook based on extrapolations of current trends, especially the structure of the housing sector and government organisations active in it. It assumes that regulatory initiatives surrounding housing remain poorly-coordinated, and illustrates how the ‘social' houses provided today might function when the occupant has no choice in the housing supplied.

Soil expansivity in Auckland
A significant fraction of new domestic construction has concrete slab on grade floors. There is uncertainty of the suitability of construction forms for such floors to suit expansive clay sites. Though NZS3604:1999 at Section 17 provides guidance for expansive soil sites, its reference to AS2780:1996 to provide the means of classification of such sites is not helpful to New Zealand designers in that this Australian Standard provides no typical profiles to allow classification to be made for major New Zealand population centres. The greater Auckland area is the site of the greatest residential growth and is recognised as having zones with expansive clay soils, and it is therefore a logical starting point to fill such a knowledge gap. The first stage of this project :

• undertook broad scope investigation of eight representative sites in the Auckland area, and reported on the expansivity of the soils from those sites in terms of AS2870:1996
• prepared representative foundation designs for typical soils in the Auckland region based on results from the above investigation, using methods of AS2870:1996 Appendix F.

A second stage was commissioned, continuing the sampling and testing at six of the original eight sites to enhance the reliability of the findings and has largely confirmed the earlier finding that the results are complex and best interpreted by geotechnical engineers, but suggest that the six sites monitored in the second phase (at Red Beach, Mairangi Bay, Howick, Otara, Manurewa and Pukekohe) would be classed as moderately expansive in terms of AS2870, and the authors conclude that some foundation types described in NZS3604 will require modification before use in such soils. Methodology for assessing the expansivity of soils at other sites is also discussed.

A consortium funded by Manukau City Council, North Shore City Council, Auckland City Council, Rodney District Council, Papakura District Council and Franklin District Council assisted the Building Research Levy in commissioning this second stage of the work from Fraser Thomas Ltd.

Flanking noise
While there is a good understanding of the need for tested acoustic separation systems to be used, especially in inter-tenancy walls, the quality of the separation is often diminished by ‘flanking noise', transmitted by paths that go around the tested system. These flanking paths can arise by virtue of the design or from site practices. A small study is measuring the effects of this in real buildings, and the next steps are to make measurements on actual buildings.

Download a copy of a University of Canterbury Engineering School background paper on flanking noise, and a summary also appeared in the April 2006 edition of BUILD.

The European standard EN12354-1 describes calculation methods for the prediction of the apparent sound reduction index between two rooms due to an airborne noise source, inclusive of flanking paths. 

The applicability of this standard to prediction of the apparent sound reduction index between two rooms in a lightweight building construction has been assessed by Jeff Mahn in a PhD project at University of Canterbury (with financial assistance from the Building Research Levy and DBH). The standard was originally developed for constructions made of heavy elements such as concrete for which it works well. However, lightweight elements such as double-leaf gypsum board walls typically do not meet the requirements of statistical energy analysis methods used in this standard.

As part of the study, correction factors and alternative calculations were proposed, but these changes could not correct for the potentially large differences between the predicted and the measured results for lightweight elements. It was concluded that the current version of the EN12354-1 standard could not be endorsed for the calculation of the apparent sound reduction index of lightweight elements. A summary of the work can be found here.

Abstracts of papers on separation of resonant and non-resonant components of the noise spectrum produced during the study can be found here. (Note that this link goes only to the J. Building Acoustics 15(2) abstracts page, not the full papers. The full papers require some acoustics knowledge to be easily understood.)