At the end of last year, the Supreme Court in University of Canterbury v Insurance Council of NZ Inc  NZSC 193 reached an interesting decision.
You may read more at:- http://www.stuff.co.nz/business/industries/64385835/Councils-can-t-force-seismic-strengthening-court-says
The gist is that the building has to be at least 33% of NBS and owners/ insurers cannot be forced to take this to 67% of the NBS. This may have affected the building consent process with the higher requirement which has now been clarified to be lower despite a council having a policy of requiring a higher percentage.
Please note the obligations under the Health & Safety in Employment Act 1992 may come into play in conjunction with the Building Act 2004. For instance owners may be liable under the former legislation due to non compliance with the later Act.
As for tenants as well as landlords, depending on the hat one wears, the lease agreement should address this matter if the building requires strengthening works to comply. Tenants need to know what their obligations are in terms of payments to the landlords. Likewise, landlords cannot unilaterally increase the strengthening requirement and expect the tenant to pay for this. Thus, it is important that the lease agreement is drafted to clarify matters. Tenants may want to do a proper due diligence to confirm any outstanding issues with a building to comply with the NBS.
I have been in the legal industry for over a decade and have broad range of experience and skills.