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“Urgent action” needed on building standards

By Helen Smith, Partner

Following the Christchurch earthquakes, a Royal Commission was established to examine issues around buildings in the Christchurch CBD and to consider the adequacy of relevant building codes and standards for the future.

It was required to issue an interim report by 11 October 2011 with recommendations to inform early decision-making on rebuilding and repair work in the recovery of Christchurch.

The Interim Report does not have an extensive list of recommendations. This is largely because it was prepared before public hearings took place, and without considering the Department of Building and Housing’s report into the failure of the PGC, Forsyth Barr, and Grand Chancellor buildings (released on 30 September 2011). The investigation into the CTV building has also not yet concluded.

But it does contain some important recommendations which have implications for not just Christchurch but the whole country.

Many relate to the design of new buildings-- and as rebuilding is already underway, it was important that these recommendations be made as soon as possible.  However, some recommendations also impact on existing buildings and are already sparking debate about the cost of strengthening work.

The comments in the Interim Report may change as the Royal Commission progresses. However, the authors have been careful not to make recommendations which are likely to be significantly impacted upon by the ongoing inquiry, particularly in relation to the catastrophic failure of the CTV and PGC buildings. The authors do, however, make recommendations which reflect their view that “ urgent action is required in respect of some aspects of current building design practice, both in Christchurch and elsewhere, to make some buildings’ elements (particularly stairs and floors in multi-storey buildings) more resilient.” They also consider immediate action is required to strengthen parts of unreinforced masonry buildings that could fail even in earthquakes less severe than those experienced in Canterbury. Given the importance of these issues and the urgency attached to the recommendations, they are unlikely to alter significantly.

Geotechnical issues

One of the main causes of the damage in Canterbury, particularly in the CBD, is the soil structure, which can be highly variable within a small distance, both horizontally and vertically.  Experts say that some of the soil beneath the CBD would have minimised the vibrations from the earthquake, while other soil would have amplified it. 

The Royal Commission refers to international best practice when considering foundation design. This means comprehensive geotechnical investigations are necessary before designing the foundations of a building, and locations with difficult soil conditions should be avoided altogether. It recommends that the Christchurch City Council require “thorough soil investigations to be carried out as a pre-requisite to foundation design”. A thorough understanding of the layering of soils and the soil properties is required down to at least 25 metres below ground level. Such information can be obtained by bores as well as other penetration tests.  These investigations will come at a cost, particularly when damage to the land due to liquefaction also has to be addressed. Soil improvement techniques should also be looked at. Although this recommendation is focussed on Christchurch, it is likely that more extensive investigations may also be required elsewhere.

An interesting recommendation is that land use and building controls in the CBD should reflect the need for care in the placement of buildings of different structural types and sizes. One of the common submissions in the relation to the draft Central City Plan was in relation to prescription and its potential to drive investors from the city. Some prescription may be required, however, in relation to the size and height of structures to be constructed on similar soils. The Royal Commission considers there are potential issues with buildings of different sizes and weights on similar soils. Regulation is recommended so that soil issues are minimised and developers and architects are being asked to take this issue into account. This has the potential to affect development within the CBD and an early appreciation of the soil conditions and any neighbouring buildings (existing or proposed) will be critical.

Foundations

The Royal Commission has concluded that no single foundation system is better than others.  Appropriate foundations will need to be carefully considered, both in respect to the structure of the soil beneath the building, and the size and height of the building.  The type of foundation that can be used in any given area may have an impact on the size of the building that can be built.  Geotechnical advice will be critical in determining an appropriate foundation design.

Architects are also being asked to consider new technologies such as base isolation and damage resistant technologies for improved seismic performance, on the basis that adopting one or more would result in “improved seismic performance of new buildings in Christchurch”. The Royal Commission considers urgent work is required to incorporate these into national standards. For now it has simply referred to a report it received from Professor Andrew Buchanan and others from the University of Canterbury, ‘Base Isolation and Damage-Resistant Technologies for Improved Seismic Performance of Buildings’. In the Royal Commission’s view, engineers and architects should be aware of the content of that report when designing new buildings. The use of new technologies will be a critical issue for all architects, engineers and developers.

Unreinforced masonry buildings

Apart from the CTV and PGC buildings, most of the deaths in the 22 February earthquake were caused by the failure of unreinforced masonry buildings.  Estimates suggest that there are still around 3,500 such buildings in New Zealand.

The Royal Commission has recommended that these buildings reduce the falling hazards by bracing chimneys, parapets, and awnings.  The buildings should also be strengthened through reinforcing the walls and installing ties between the roofs and walls, and in some cases installing ties at all floors.

This is a significant cost but one which it considers is justified and which affects all of New Zealand.

Stairs

The Forsyth Barr building, and others, experienced the structural failure of the stairs, which stopped most, if not all, workers from evacuating.  Both the Royal Commission and the DHB report have considered this issue.

The current design standard for inter-storey drift, which is the relevant criteria for stairs, did not allow for the peak acceleration at the level experienced.  The Royal Commission recommends that the standard be amended so that stairs, ramps and other means of leaving a building are built to cope with more movement.  This standard will apply New Zealand-wide.

Insurance

The Royal Commission’s recommendations should produce safer buildings, but the cost of rebuilding or repairing in accordance with them may be significant.

Most insurance policies for material damage cover the cost of repairs or replacement of a building, including any additional costs required to comply with any statute or local body regulation.  Although the Royal Commission recommends urgent changes are required to current design standards, they remain simply recommendations at this stage. The changes are not yet supported by statute or local body regulation. Insurers and building owners may potentially dispute who will pay for these increased safety measures, at least until the building standards are formally amended. However, given the importance of the issue and the inevitability that building standards will be amended (and quickly) either under the CERA legislation or the Building Act, we suspect the issue is not likely to arise or, at least, is one which is capable of resolution.

Helen Smith is a partner specialising in Litigation and Dispute Resolution. h.smith@DuncanCotterill.com

Disclaimer: the content of this article is general in nature and not intended as a substitute for specific professional advice on any matter and should not be relied upon for that purpose.