The best place to start when looking for information on how house repairs should be assessed and carried out is the Department of Building and Housing's booklet Guidance on house repairs and reconstruction following the Canterbury earthquake - A summary of geotechnical and structural engineering recommendations to guide house repairs and reconstruction.
There are eight main headings for the contents of the guide:
1. Introduction and Scope
2. Summary of Insurance and Regulatory Requirements
3. Future Expectations for Land and Buildings
4. Repair Criteria and Assessment Approaches
5. Repairing Houses
6. Rebuilding Houses
7. Recommended Arrangements for Engineering Input
8. Flood Risk and Floor Levels
plus some appendices.
If your house has suffered damage to its foundations then Chapter 4 is the one to read. It starts with a simple description of the types of settlement a house can experience, then provides a table of recommended criteria against which a particular house type can be assessed and the repair work that will be required (or maybe a rebuild instead!).
Chapter 5 describes the various repair methods and Appendices 3 and 4 outline repair methods.
The booklet can be down loaded from DBH here.