There has been a lot of comment lately about whether the building code is fit for purpose(1). This is wrapped up in the media/PR drive around "risk based pricing" and coincides with concerns around the safety of modern compliant buildings under earthquake conditions. The argument is that new, fully code compliant buildings failed in the Canterbury Earthquake sequence (CES) and in Wellington during the Kaikoura Earthquake, therefore, the code must be flawed or faulty. The Insurance Council (ICNZ) is pushing this line, with the view that in California and Japan the absence of earthquake insurance means buildings are built stronger driven by economic drivers. Is this view correct? It all sounds pretty dire, right?
In my view the arguments made fail to consider how the building code works and exaggerate the problem.
How does the building code work?
Since the 1990s the building code specifies performance criteria for buildings, (previously it was prescriptive, literally telling builders/engineers how to build). This means that a building must be designed to withstand certain conditions (weather, seismic loading, longevity) specific to the environment it sits in and as well as this the building must protect the safety of those using it if there is a catastrophic event. The performance mechanisms used to do this are by specifying how buildings perform for the types of event they might be expected to face at three levels;
- a Serviceabililty Limit State (SLS) event is expected to occur with around 90 per cent probability in the 50-year design life of a typical building;
- an Ultimate Limit State (ULS) event is expected to have 10 per cent probability of occurrence 50-year design life of a typical building
- a Maximum Considered Event (MCE) event is expected to have approximately a 2 per cent probability of occurrence in 50-year design life of a typical building
An SLS event might occur several times during a buildings lifetime (say a one in 25 year earthquake or windstorm). Whereas a ULS event is a bigger more catastrophic event, for example a once in a century storm, or an earthquake of a strength which would recur every 100-500 years. An MCE event is the big one that 1000-2500 yearly monster. Within these categories the building should perform as follows: an SLS event, the building should sustain no significant damage; a ULS event, it may well be extensively damaged, but the inhabitants will survive without significant injury; and an MCS will write the building off, but it shouldn't fall down so the inhabitant are alive. So despite what the ICNZ says, our buildings ARE designed to protect economic values but the protection of life is prioritised (I'll comment below on what we should learn and what is less accurate). This makes sense, as engineering building for an MCS event, which is very unlikely to occur in its lifespan would be counterproductive. Some buildings ARE engineered to this level, essential power infrastructure, hospitals and important government buildings, but it is prohibitively expensive. One consideration would be that if you build an office block in down town Palmerston North which survives an MCS event undamaged, you'll lose all your money anyway, as the rest of the city will be wrecked and your tenants will all move elsewhere.
Now an important consideration is that environmental hazards are different throughout New Zealand; a storm with 150km gusts is an SLS event in Wellington, but would approach ULS level in other places. Christchurch buildings are designed to withstand moderate snow loads, but Auckland buildings are not. With Earthquakes the application of the code means that a building in Hamilton (apparently the safest place in New Zealand) is engineered for the same repeat interval of seismic risk as in Wellington. So an earthquake of a strength which would barely be noticed in heavily engineered Wellington would devastate Hamilton. Despite what we might believe, EVERY PART of NZ has Earthquake hazards. Even places which are not considered seismic have earthquake hazard; before 2010, the most expensive earthquake for the insurance industry in Australasia was the 1989 Newcastle earthquake, a 5.6 shake which killed 13 and caused an insured loss of over AU$1 Billion.
So when we are told that the Building code is designed to save lives not economic value, this is only true in a massive once every few centuries event.
How are the performance criteria applied you ask? Either an existing design standard is applied (a big book of prescriptions on how to, for instance, build a wall) or an engineer designs and calculates the particular building feature and signs off that feature meets the performance criteria, Council then reviews and approves design (More on this later).
Exaggerating the risks
The current furore around building standards comes from some particular circumstances: The CES events and the unpreparedness of Christchurch for large earthquakes, the losses of life in the CTV and PGG buildings, and the performance of a particular set of buildings in Wellington; highly ductile concrete buildings on soft/variable ground, during the 2016 Kaikoura quake (and to a lesser degree the 2013 Seddon event). The problems with the current discussion is the focus of most commentators on these circumstances without acknowledging that these were the exceptions not the rule for the performance of buildings in these events, and I take issue with this on a number of grounds:
- The issues in the CES events arose in part because Christchurch (pre-2010) was considered moderate seismic risk and its buildings was designed accordingly, despite this the majority of the housing and building stock performed reasonably well, especially considering that the CES events were six SLS-ULS level events over two years. Wellington's building stock in comparison is and was stronger for two reasons;
- in 1942, the Wairarapa quake knocked down most of the old poorly maintained un-reinforced masonry (URM) buildings in Wellington (some 10,000 buildings were damaged). These were the type of older buildings that killed fell into the streets in the central city, Addington and elsewhere around Christchurch.
- since the 1940s buildings in Wellington have been zoned as high seismic risk and have as a result been more strongly engineered as a result.
- Around 1 in 4 buildings in Christchurch was damaged by CES events and the bulk of the damage was minor. HOWEVER, the insurance response to this damage was made more complicated and expensive by the establishment of the red zones (which led to payments being made where they might not otherwise have been) and by the poor assessment of risk by insurers prior to the earthquakes, leading to old, poorly maintained buildings, at the end of, or beyond, their useful lives being insured for full replacement. So in numerous instances buildings which were practically falling down BEFORE the earthquakes, which sustained damage, were replaced with shiny new modern buildings (a great deal for the owner). The current discussion must factor these issues in.
- The insurance industry has effectively admitted that it wasn't pricing Earthquake risk in Christchurch properly before 2010, and at the Wellington Mayoral Forum, ICNZ threw out the impressive figure that the CES cost the insurance industry 100 years of earthquake premiums. This is an impressive figure, HOWEVER, paying a 100 years of premiums for a once in a 100 year event IS HOW RISK PRICING WORKS!
- The tragic failures of the PGG and CTV building were outright design failures, which should never have been approved. There were failures of the design system, outright fraud in the CTV case, a failure of the consenting system, and a failure of the inspections which occurred after the the September 2010 earthquake. These are NOT failures of the building code.
- During the Kaikoura quake the failure of three modern buildings in Wellington is shocking, and shouldn't have happened. However, these buildings were all of a particular type of design; with hollow form concrete floors, and a particular type of "pigtail" structural fixing connecting the floors to the building. These failures aren't indicative of the majority of the building stock, which again, largely performed well. It's worth noting that the engineering issues with these types of construction were known about 3 years before the earthquake occurred and for Statistic house specific concerns were raised well prior to the earthquake, this does not seem to have factored into the insurers decision to issue coverage. It's also worth noting that several buildings which are scheduled for demolition due to similar design issues (the Wellington Central library for one) were not damaged during the Kaikoura earthquake.
- The damage in Wellington from the Kaikoura earthquakes was concentrated to a particular area of the city due to a mixture of soft and reclaimed ground. However, the peak ground accelerationexperienced during the Kaikoura quake in Wellington exceeded SLS and approached ULS levels. Despite these levels of shaking the vast majority of the building stock (even unreinforced masonry buildings which had already been yellow stickered) was undamaged.
So I think the issues are overstated, but, there are issues with the building industry which need to be addressed.
- As seen with the confusion and concerns over the new building at 230 High Street Christchurch(2), structural issues can be complicated. In this particular case there is a new building, 5 engineering firms, and a variety of opinions over whether the building meets code criteria. The inability of engineers to agree over something this essential is of real concern. The lack of agreement has been an ongoing problem in Earthquake litigation in Christchurch for number of years. It seems that certain engineering consultancies have become habitually argumentative as a result (worse than lawyers!). We all rely on engineers every time we step into a building, the profession needs to do better.
- Councils have a part to play, there is inconsistency between (and occasionally within) councils about the application of the legislation, greater consistency is needed.
- Central Government needs to do a better job. MBIE should step up its game and support Councils and the industry with better and more forward looking structural planning, better guidelines for various issues, and a more cohesive approach (MBIE is a siloed beast and it can be hard to navigate at the best of times). Given looming climate issues including sea level rise, this has to happen now.
- Construction is a mess in New Zealand, it appears that 20 plus years of leaky building issues have not led to real structural change. We are doing a poor job or training and retaining builders and the focus of the industry is only slowly moving towards building the type of houses the country needs.