Foundations on expansive soils and application of ‘good ground’ definition

- Ross Roberts

Expansive Soils

In the November 2018 update MBIE proposed to revoke Simple House Acceptable Solution SH/AS1. MBIE agreed with feedback received during that consultation that the information in SH/AS1 for foundation design on expansive soils should be retained. MBIE is proposing to move this information into Acceptable Solution B1/AS1, making it a mainstream solution, and revoke SH/AS1.

They are now requesting feedback on this.

Good ground definition

MBIE are already thinking about the content for next bi-annual Building Code update programme in November 2019. This third update will continue MBIE’s work to support housing densification and catching up our Acceptable Solutions and Verification Methods to industry practise. The consultation package is looking at 22 possible changes, including the area described below.

MBIE wants to ensure suitable foundations are being used on ground that has the potential for liquefaction or lateral spread reducing the risk of damage to buildings and occupiers. This proposed change incorporates lessons learned from the Canterbury Earthquake Sequence, particularly about the effects of liquefaction and lateral spread. By revising the application of the ‘good ground’ definition, MBIE will provide greater clarity for how foundations are to be designed and constructed in regions across New Zealand that are subject to known liquefaction and/or lateral spread potential. The Acceptable Solution B1/AS1 will extend the regions where liquefaction and lateral spread of soil are excluded from the definition. The clarification being considered will allow the consistent application of the ‘good ground’ definition across New Zealand.

Giving feedback

View the full proposals and information on how to provide feedback on the MBIE website

You can also discuss with your colleagues here to help inform feedback by others.

Ross Roberts
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