Media release - Guidance for repairing and rebuilding foundations for homes in TC3 areas of Canterbury published
27 April 2012: The Department of Building and Housing (the Department) has today published guidance on foundation repairs and reconstruction for houses in Foundation Technical Category 3 (TC3) areas of Canterbury.
The guidance is an appendix to the Department’s Revised guidance on repairing and rebuilding houses affected by the Canterbury earthquake sequence published in November 2011.
It is intended for professional geotechnical and structural engineers tasked with designing appropriate foundation systems for individual properties.
Department of Building and Housing Deputy Chief Executive David Kelly says the guidance provides information on the relevant engineering principles and design parameters for foundation repairs and reconstruction in TC3.
“It aims to provide robust and well-balanced engineering solutions that will reduce the risk of injury to people and damage to homes in future earthquakes.”
The guidance provides options for the replacement and repair of damaged foundations. For new or replacement foundations it specifies three types of foundation design. These are: deep piles, site ground improvements, and surface structures with shallow foundations.
Each of these foundation types have different capabilities to accommodate various levels of vertical settlement and lateral spreading, and place different constraints on the type of dwelling that the foundation can support. For example:
- Deep piles – no height and/or material constraints likely, but they won’t be suitable in some situations.
- Site ground improvements – will place limits on some two-storey dwellings with heavy walls and irregular plans. For example, this option may not be suitable for a two-storey brick veneer and tile house.
- Surface structures with shallow foundations –suitable only for lightweight homes that have standard design features, and where there is only minor-to-moderate potential for future settlement and lateral spreading.
Mr Kelly says Chartered Professional Geotechnical Engineers will be able to determine what foundation type is appropriate for each property based on information obtained from geotechnical assessments.
“Ultimately, decisions about foundation repairs or reconstruction will need to be made by homeowners and their insurers based on professional advice.”
The guidance document can be downloaded from the Department’s website at http://www.dbh.govt.nz/guidance-on-repairs-after-earthquake
For further information contact Susan Owens, Canterbury Earthquake Response Communications Manager, phone 04 817 4242 or 027 501 5828.