Author Archives: Hugo

Royal Commission, recommendations and MBIE

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The Royal Commission considers that there must be greater focus on geotechnical investigations to reduce the risk of unsatisfactory foundation performance. 

This is my letter to MBIE as I am concerned about these issues.

I have been looking at the Recommendations by the Royal Commission.
One of them is the following.
“Ground-improvement techniques used as part of the foundation system for a multistory building should have a proven performance in earthquake case studies.”

I live on a highly liquefiable land and we have 38m down to gravel. Land measures at 10.7m, highest tide in the area is supposedly at 11.2m
ULS subsidence is measured to be 340-400mm down to at least 20m depth. Lateral spreading 70-200cm.

Are you aware of any ground improvements with a proven performance in earthquake studies that would solve this problem?
Have any tests been made? Are there any solutions?

Then in general for TC3 ground improvements in the eastern suburbs.
In general the depth down to gravel is 30-40m.
Liquefaction induced settlement is down to at least 20m.
Any gravel platform or ribraft solutions on this land is likely to increase the settlement based on houses that have sunk into the ground in these areas.

The geotech reports I have seen so far are not according to any acceptable standard.
Typically assume drained soil, Exclude Liquefaction probability, exclude lateral spreading, assume no building on site, stated preliminary, Exclude the Z factor (seismic risk)
Commonly only calculate settlement down to 10 meters when it is known that subsidence reaches far greater depth.
Designers and engineers are excluded from all liability in the current building act. The only thing that is monitoring them is their own code of conduct.
I think it would be fair to say that these practices are not acceptable by society.
What is MBIE opinion of these practices?
What can be done to stop this?

What ground improvement solutions are proposed for these situations and how have they been tested?
The seismic risk in this area is extreme. Two active fault lines are under these suburbs and we have had a downward tectonic movement here.

I look forward to your response.

Update to come.

Please be careful if your property is subject to Hazards

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Please be careful when considering cash settlements if your land is subject to hazards. The revised District Plan may render your land un-usable. The district plan will identify where repairs or rebuilds are allowed and where no development is allowed.
http://www.stuff.co.nz/the-press/business/the-rebuild/9678151/City-urged-to-take-harder-line

CCC has legal obligations to follow the New Zealand Coastal Policy Statement 2010 – 

The District Plan is Councils ability to limit development in natural hazard areas

This opinion provides advice on the potential liability councils may face as a result of re-drawing hazards lines/zones in coastal areas and flood plains. The advice covers liability risk for councils in terms of the RMA, Building Act and for general information requests under LGOIMA, PIMs and LIMs. The advice also addresses the question of what defines ‘best available information.’

See legal opinion here.
http://www.lgnz.co.nz/home/our-work/our-policy-positions/environment-and-regulation/natural-hazards/

This is likely to affect hundreds if not thousands of homes in Christchurch.

Floor Area of your property

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The term floor area has a legal definition as per the New Zealand building code.

“floor area, in relation to a building, means the floor area (expressed in square metres) of all interior spaces used for activities normally associated with domestic living”

This is in harmony with how calculations of “floor area” are on architectural drawings for building work. Commonly information from building plans is used when insurance is arranged. Floor Area is the term used in insurance contracts.

If you have legal plans of your property, (available from Council) you can rely on those figures.

Houses are insured on “Floor Area” not to be confused with area of house. Check your policy.
Having a 100m2 groundfloor and 10m2 room in roof cavity does not require insurance of 230m2 “Floor Area”. 
But 110m2 as per building plans.
House area is something that has appeared after the earthquakes. Check out the ANZ site here, second reference is to the building plans that is the correct one.
Then they offer you a guide to measure the outside.
What is the purpose of a Code of Conduct if they practice in this way.

https://comms.anz.co.nz/insurance/detail/article/15033/0/0/how-to-measure-the-floor-area-of-your-house.html