The Department of Building and Housing (DBH) today released a publication Updated guidance for the repair and reconstruction of homes in Canterbury. A PDF copy can be found here. It is an update of a document released in December 2010.
Time will be needed to identify exactly what the changes mean for property owners. From a very quick skim through it appears that, in addition to new material on foundations (both building and patching them), the criteria in this amended document are “less onerous” than in the original version.
As a technical document it outlines what procedures are considered appropriate for various types of houses, the structural damage incurred, and the land category. While it describes what is permitted and recommended, one extremely important issue is only briefly addressed: the obligations of the insurer (EQC or a private insurance company) towards the policy holder.
Irrespective of what DBH may specify as suitable and satisfactory practices and solutions, they can only be applied if they meet the insurers obligations to the property owner. As a minimum these approaches can only be applied if they restore the property (house and foundations) to at least the condition it was in on the 3rd of September 2010. A “less onerous” solution may fall short of meeting this requirement e.g patching something that has cracked or broken is not the same as restoration or like new.
One area where this tension may arise involves concrete slab foundations in TC1 and TC2 areas (TC3 properties will require site specific investigations). A particularly common problem with new houses has been cracking of the foundation slab. An economical solution would be to repair these foundations where ever possible. This is addressed in Appendix 4 of the publication.
Research has been carried out overseas on the use of resins and grouts to repair cracks caused by slab shrinkage. The DBH has investigated these solutions and outlines how they could be applied in Christchurch to fix cracks varying between 1 and 50 millimetres or more.
It can be anticipated that there will be times when those working for EQC or insurance companies will suggest or insist on repairing a slab. The use of resins and grouts may be acceptable as a consequence of slab shrinkage over a period of years. The same solutions do not meet the criteria of restoring a foundation back to the way it was prior to the earthquakes. An additional consideration is the following, which is highlighted on page 125, and precedes the description of the repair solutions mentioned above:
Please note: it cannot be assured that a crack will
not reopen after the completion of any of the
processes described below.
While repairers will be keen to point out that product X carries a warranty for a long period of time, the warranty is pretty much worthless unless either EQC or your insurance company agree to underwrite it.
Should you need to call on the warranty because of a problem, you could find yourself in the middle of a dispute between the product maker and whoever applied it as to who was at fault. It could be that either or both businesses disappear and there is no company around to honour the warranty. This is not the level of structural certainty that existed on the 3rd of September.
Even people living in TC1 areas should be wary of any suggestion that cracks be repaired. Peace of mind and equity are at stake, so seek advice should the topic be raised.
If it wasn’t broken on the 3rd of September 2010 then you have every right to expect better than a patch-up job.
Chapter headings are:
Part A: Technical guidance
2. Foundation assessment criteria and approaches
Land on the flat
3. Technical categorisation of the Green Zone on the flat
4. Repairing house foundations
5. New foundations
6. Hillside properties and retaining walls
7. Superstructure assessment and repair recommendations
Part B: Technical information
8. Insurance and regulatory requirements
9. Observed land and building performance
10. Future liquefaction performance expectations for land and buildings
Appendices and References
A1 Re-levelling systems and outline method statements for re-levelling and repairing foundations and floors in tc1 and tc2
A2 Outline method statements for replacing foundations and slab-on-grade floors in tc1 and tc2
A3 Assessment and repair options for chimneys damaged in the Canterbury earthquake sequence
A4 Assessment and repair options for concrete floor slabs damaged in the Canterbury earthquake sequence
B1 Summary of the effects of liquefaction
B2 Guidelines for the investigation and assessment of subdivisions