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 Earthquake Repair and Rebuilding Information

build126.jpgWelcome to our earthquake repair information page, designed to provide you with useful links, research and advice relating to building repairs and rebuilding work in the wake of the Canterbury earthquakes.

On this page:

Information sources: Canterbury Earthquakes Royal Commission, MBIE Building and Housing Group, IPENZ, New Zealand Legislation, NZ Society for Earthquake Engineering, Standards New Zealand 

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Recently, BRANZ used a photo of 16 Rapanui Lane, Christchurch, on our website and in Bulletin 551 Learnings from the Canterbury Earthquakes. This house was constructed using specific engineering design principles and did not present damage from an earthquake. The photo was used to demonstrate the type of house that could have presented damage from an earthquake due to its location and design type. BRANZ regrets the use of this photo in the context provided. An updated Bulletin 551 will be available from our website shortly.

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LEGISLATION AND STANDARDS

Building Act 2004
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Meaning of earthquake-prone building (s122)
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Building consent not required in certain cases (s41(1)c(i)) ... for the purpose of saving or protecting life or health or preventing serious damage to property
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Owner must apply for certificate of acceptance if building work carried out urgently (s42)
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Powers of territorial authorities in respect of dangerous, earthquake-prone, or insanitary buildings (s124-130)

Building Regulations 2005
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Earthquake-prone buildings: moderate earthquake defined (s7)

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EARTHQUAKE-PRONE BUILDING POLICIES

MBIE Building and Housing Group web page: Earthquake-prone buildings 
To make buildings safer to use in the future, the Building Act 2004 introduced provisions to improve the likelihood of existing buildings withstanding earthquakes including the requirement that territorial authorities develop a policy on earthquake-prone buildings.

Google search: Territorial authorities' earthquake-prone buildings policies

Earthquake-prone buildings (Build 109 Dec 2008/Jan 2009) Free download
Recently, councils have been required to develop policies to deal with earthquake-prone buildings. The earthquake in Gisborne was a good opportunity to see how valid the approach taken has proved to be.­­­­­­­­­­

DBH Determination 2010/133: The exercise of the powers of an authority to issue a notice under section 124 of the Act regarding a building considered to be earthquake prone 

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BUILDING PERFORMANCE

Liquefaction.jpgIPENZ Canterbury earthquake fact sheets (March 2011)
The Institution of Professional Engineers New Zealand (IPENZ) is the professional body that represents professional engineers from all disciplines in New Zealand. In response to Member suggestions and with the help of the New Zealand Geotechnical Society and the New Zealand Society for Earthquake Engineering, fact sheets have been prepared giving an overview of the February 22 Christchurch earthquake and performance of engineered systems, the building safety evaluation process and liquefaction. 
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Download fact sheet: Christchurch earthquake - an overview
- Download fact sheet: Building safety evaluation
- Download fact sheet: Liquefaction
- Download all fact sheets

Canterbury earthquakes (Build 126 Oct/Nov 2011) Free download
Everything changed in Canterbury when the 7.1 magnitude earthquake struck on 4 September 2010 and then the 6.3, which claimed 181 lives, on 22 February 2011. Major damage to buildings, rockfalls and landslips, liquefaction and major infrastructure damage has left an estimated $7.1 billion EQC bill. The clean-up continues as steps towards the recovery gain pace. Articles: Christchurch rebuild > Building costs > Where are the skills coming from? > Suppliers prepared for the hard graft ahead > Legislation to facilitate recovery > BRANZ busy in Canterbury > Army of tradespeople support recovery > Unreinforced clay brick masonry buildings > Massive demolition site > Hotel Grand Chancellor demolition > Temporary villages > Business as usual at uni > Helping Christchurch build back better > CERA Recovery Strategy > Central city recovery > Ten thoughts for Christchurch > WCC assesses quake-prone buildings

On the ground in Christchurch (Build 123 April/May 2011) Free download
The 6.3 magnitude earthquake that struck Christchurch on 22 February 2011 and the many aftershocks have been an enormous test of the performance of buildings. BRANZ structural engineers provide some initial thoughts on how houses performed.

House performance in the Canterbury earthquake (Build 121 Dec 2010/Jan 2011) Free download
How did residential houses (mainly single-storey and 2-storey houses) perform in the magnitude 7.1 Darfield earthquake on 4 September 2010? Here are some observations from those on the ground in the early days after the major earthquake.
          

Operation Suburb (Sept 2011)
Graeme Beattie, BRANZ Principal Engineer, outlines some of the learnings from Operation Suburb in Christchurch, where BRANZ engineers assisted in assessing building damage. 

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Canterbury Earthquakes Royal Commission: The Canterbury Earthquakes: Answers to critical questions about buildings (2011)
The Canterbury region has had a series of extremely difficult challenges as a result of the 4th of September earthquake and its associated aftershocks. This has led to questions related to the expected building performance, as well as their actual behaviour, in an earthquake. As a result, the following answers have been prepared by the Royal Society of New Zealand, the Institution of Professional Engineers New Zealand, the Structural Engineering Society New Zealand, the New Zealand Geotechnical Society and the New Zealand Society for Earthquake Engineering, who have co-ordinated science and engineering expertise from across New Zealand.

NZ Society for Earthquake Engineering conference papers 

  • The performance of residential houses in the Darfield earthquake of 4 September 2010 (April 2011) The housing stock in the Christchurch area covers an age range from the late 19th century until the present day. A database of randomly sampled houses has been established and surveyed, in conjunction with the EQC inspection process. The paper describes the findings of the survey and comments on the effectiveness of the past and current design standards for such structures with regard to earthquake resistance. The need for modifications to the current standards is discussed.
  • Seismic resistance of brick veneer under face loading (December 2009) Recent full-scale cyclic and shake tests by the authors have shown that modern single and two-storey brick veneer New Zealand houses will perform very well under in-plane testing and can be relied upon to carry a significant portion of the seismic design load. After a design level earthquake, cracking is expected to be almost imperceptible, and even after a maximum considered event, little or no veneer collapse is expected. Cracks should be repairable simply by raking out mortar along crack lines and repointing.

SR218 Report on a short study tour of houses following the 15 July 2009 Fiordland earthquake (2010) Free download
A visit was made by BRANZ to several houses in the Queenstown and Wanaka areas that had been surveyed by EQC Damage Assessors after the 15 July 2009 Fiordland earthquake. The aim of the visit is to determine whether houses clad with EIFS systems suffered greater internal damage than those clad with weatherboards or brick veneer.

Capital Quake explores earthquake issues (Build 102 Oct/Nov 2007) Free download
Would we be prepared if the 'big one' struck? An earthquake simulation exercise in Wellington revealed that a lot of work is still required. 

BU444 Lessons from the 1987 Edgecumbe earthquake (December 2003) Buy
Houses on simple piles are vulnerable to foundation failure unless adequate bracing of the sub-floor system is provided. Houses constructed in accordance with the requirements of NZS 3604 and also well-built older houses survived the earthquake without structural damage. Different types of shaking result when separate parts of a building are founded on different types of foundation. Often damage will occur at the junction of the differing parts. Chimneys are particularly vulnerable. It is essential that precase chimney units are properly reinforced, and that the chimney is adequately attached to the structure or is designed to stand independently.

SR54 Report on racking resistance of long sheathed timber-framed walls with openings (1993) Free download
This study forms the first phase of an investigation into the wind and earthquake racking resistance for timber-framed New Zealand houses from roof to ground floor level. This report is intended for structural engineers, architects, designers, manufacturers and others researching earthquake and wind resistance on low-rise buildings.

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REPAIR AND CONSTRUCTION - GENERAL 

DBH publication: Revised guidance on repairing and rebuilding houses affected by the Canterbury earthquake sequence (November 2011) 
(Note that this updates the previously issued document: Guidance on repairing and rebuilding houses affected by the Canterbury earthquake sequence.)
The principal objective of this document is to provide building repair and reconstruction solutions and options that:

  • are appropriate to the level of land and building damage experienced
  • take account of the likely future performance of the ground
  • meet Building Act and Building Code requirements
  • are acceptable to insurers and property owners.

SR158 Repair and reinstatement of earthquake-damaged houses - derivation of repair techniques - phase III (stucco) (2006) Free download
Experimental investigations have been carried out to replicate the damage sustained in earthquakes and to derive cost-effective and practical repair procedures for stucco wall claddings, softboard ceiling linings, hardboard ceiling linings, and lath and plaster walls. An investigation of a process of re-levelling structures using a ground injection technique has been undertaken. Surveys have also been carried out on a selection of houses with settled foundations and/or foundation slabs that have been re-levelled using this process to ascertain the permanence of the solution. With reference to the claims files held by the Earthquake Commission following the 2003 Te Anau earthquake, an attempt was made to identify commonly used processes for the repair of very minor damage to the interior of properties. 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.

SR123 Repair and reinstatement of earthquake-damaged houses - derivation of repair techniques - phase II (brick veneer, EIFS, fibre-cement coated sheets) (2003) Free download
This study report builds on the information contained in BRANZ Study Report 100 Repair and reinstatement of earthquake-damaged houses - derivation of repair techniques - phase I. Experimental investigations have been carried out to replicate the damage sustained by houses in earthquakes and to derive cost-effective and practical repair procedures for a number of building elements. This report includes investigations into: * walls reliant only on the internal linings for providing lateral restraint to the structure * brick veneer walls * exterior insulation and finishing systems (EIFS), weatherboard and monolithic exterior claddings. Methods of straightening a house that has been left with a residual racking displacement were 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.

SR100 Repair and reinstatement of earthquake-damaged houses - derivation of repair techniques - phase I (exterior wall clad with sheet sheathing, a braced pile foundation system, a brick veneer corner and gypsum plasterboard lined interior walls of a 1960s two-storey duplex housing unit) (2001) Free download
This report describes the development of procedures for the repair after earthquake of a selection of structural elements of domestic housing. Systems considered include an exterior wall clad with sheet sheathing, a braced pile foundation system, a brick veneer corner and gypsum plasterboard-lined interior walls of a 1960s two-storey duplex unit.

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REPAIR AND CONSTRUCTION - SLABS AND FOUNDATIONS

Amended version of B1/AS1
On 1 August 2011, the DBH formally introduced the amended versions of the Building Code Compliance Document covering clause B1 Structure (B1/AS1), which modifies several New Zealand standards. The changes bring the documents into line with the latest standards, reflect the latest studies and research, respond to changes in building practices and broaden the range of solutions available. From 1 February 2012, only the new version can be used. Check the requirements of clause B1 Structure incorporating Amendment 11.

DBH publication: Guidance on reinforcement for concrete slabs-on-ground (August 2011)
B1/AS1 clause 3.1.8 requires concrete slabs on ground constructed in accordance with NZS 3604:2011 on good ground to be reinforced with a minimum of 2.27 kg/m2 of Grade 500E reinforcing mesh fabric conforming with AS/NZS 4671. However, Grade 500E reinforcing mesh fabric is not yet readily available in the market. Until it becomes readily available, the DBH have advised that slabs can be reinforced with either Grade 300E - D10 reinforcing steel bars (conforming with AS/NZS 4671) at 300 mm centres each way with 30 mm top cover, or Grade 300E - D12 reinforcing steel bars (conforming to AS/NZS 4671) at 450 mm centres each way with 30 mm top cover.

BU545 Key changes to B1/AS1 and E2/AS1 (February 2012) Buy
Significant changes to the New Zealand Building Code compliance documents for B1 Structure and E2 External moisture came into effect on 1 August 2011. This bulletin highlights some of the key changes that need to be considered in the design of the building structure and building envelope.

BU536.jpgBU536 Upgrading piled foundations to resist earthquakes (June 2011) Buy
Older houses with piled foundations without subfloor bracing can be particularly vulnerable to damage in earthquakes. This bulletin discusses options for upgrading the foundations to reduce the risks of earthquake damage. This bulletin does not deal with foundation damage resulting from liquefaction.

BU535 Repairing cracks in concrete (June 2011) Buy
A satisfactory repair requires correct diagnosis of the cause, together with an understanding of the repair materials and processes. Repairs should be carried out by experienced operators. Some materials only give you one chance at getting it right.

Strengthening piled foundations (Build 121 Dec 2010/Jan 2011) Free download
The recent earthquake in Canterbury was a wake-up call for the rest of the country. Owners of pre-1978 houses with piled foundations should be asking themselves if their foundations need checking and upgrading.

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REPAIR AND CONSTRUCTION - WALLS

Repairing plasterboard after an earthquake
Stuart Thurston, BRANZ Structural Engineer, demonstrates some of the testing methods, results and repair strategies as detailed in BRANZ Bulletin 548.

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BU548 Repairing plasterboard after an earthquake - Free download
After the Canterbury earthquakes, some homeowners reported that their houses were noisier than before. This bulletin provides guidelines for repairing plasterboard-lined walls to assist reinstating strength and stiffness and to help modify this effect. It is recommended that a building bracing assessment is carried out before committing to repairs if the plasterboard bracing system has been damaged to the extent that it must be replaced.

Repairing earthquake-damaged wall linings (Build 126 Oct/Nov 2011) Free download
Many Canterbury houses have lost stiffness and strength following the earthquakes. Repairs to gypsum plasterboard linings need to restore this to prevent future small events repeating the cracking and damage.

Do earthquakes damage fire protection walls? (Build 104 Feb/March 2008) Free download
Major earthquakes are often followed by fires. BRANZ recently put some plasterboard-lined partitions through a simulated earthquake then fire-resistance testing to investigate their post-earthquake fire performance.

Research projects @ October 2012

Download this PDF file with details of current BRANZ and non-BRANZ earthquake-related research projects.

Watch the world's largest shake test in Japan

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 Earthquake Info

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