Guidance on house repairs and reconstruction following the Canterbury earthquake

Introduction

This document, issued by the Department of Building and Housing, provides technical guidance for repairing and rebuilding houses in the Canterbury region following the Canterbury earthquake. Publication of this document is a part of the Government's coordinated response during the transition to long-term recovery in Canterbury. The document supports this recovery by giving consistent engineering solutions that are robust, well considered and balance costs and risks.

The Canterbury earthquake of 4 September 2010 (sometimes referred to as the Darfield earthquake) was an internationally significant event that focused attention on damage to residential properties from liquefaction and lateral spreading. Approximately 160,000 insurance claims had been submitted to the Earthquake Commission (EQC) by early December 2010. Of these, approximately 16,000 of the claims for damage are likely to have a land component. The majority of damaged dwellings will have minor damage including damaged chimneys and superficial cracking to cladding/linings.

The volume of repair and reconstruction activity will place challenges on the insurance assessment, engineering design, construction and consenting capacity available. The reconstruction will put pressure on New Zealand's engineering resources, both structural and geotechnical, to develop specific solutions on a house-by-house basis in the normal manner. There will also be pressure on councils to process large volumes of consent applications. This may result in delays to homeowners and slow the re-establishment of the most affected communities. Insurers and reinsurers need confidence that the rebuilding work is robust without unnecessary expenses.

Overseas experience in recovery demonstrates how delays and additional costs can occur if designers, insurers and councils have different perspectives that can lead to redesign and confusion.

The guidance aims to encourage consistency of approach and to avoid unnecessary and costly investigations and design for each property. It takes a prudent approach that is mindful of costs and risks. It provides solutions and construction methods that will meet the requirements of the Building Act and Building Code while avoiding "over-design" and "over investigation" where this is not warranted. Independent costing advice estimates a strong positive benefit to cost in following the proposals in this document.

Following the methods of solutions proposed in the document is not mandatory. Different and improved details and methods may well be developed as the recovery proceeds. The earthquake and its effects are complex. Investigations into the full picture on how residential structures responded to liquefaction effects are ongoing. It may well be that some aspects of the recommendations in the document are added to or changed over time.

The latest version of this document is available from website www.dbh.govt.nz(external link) and may be updated from time to time.