Our building stock could look radically different in the next few years as owners and architects introduce new seismic elements, an expert says.
The Government is proposing seismic assessment of all commercial and high-rise, multi-unit buildings - believed to be 193,000 properties. The focus will be on buildings built before 1976.
Those not upgraded to withstand a moderate-sized earthquake within 10 years of assessment would have to be demolished. It is estimated between 15,000 and 25,000 buildings will have to be strengthened or demolished, and this number could rise.
Andrew Cleland, chief executive of the Wellington-headquartered Institution of Professional Engineers, says earthquake bracing or strengthening elements on buildings could be exposed to reassure people that they are entering a strong building. Cross-bracings on walls could be exposed, steel beams in ceilings visible, ply to secure unreinforced brick masonry made obvious and even damping systems at the top of buildings to absorb earthquake energy could become design features.
"It will be highly variable - some people will want to hide these elements, some people will want to show them off," Mr Cleland said.
Steel bolts driven through old facades might become a feature on some structures while others will seek to disguise in the hope of retaining aspects of an old building's character.
"Most of the foundation stuff, you just won't see it," he says, although creating tough systems like those used on Te Papa might cause interest.
"It will be down to the individual building owner or architect, to what extent they want to use extra strengthening as a feature," he says.
Buildings will look different due to technological and design changes, regardless of tougher seismic standards. A group of 80 fourth-year Victoria University architecture students spent the last half of last year rethinking Wellington's iconic Cuba St and how it might look by 2035, studying 72 heritage buildings, including 39 registered with the Historic Places Trust.
Some recommended demolition but used heritage elements in new ultra-modern blocks. Others mapped out how to preserve and strengthen buildings. Others recommended typing groups of buildings together, or demolishing everything except a facade.
Associate Professor Andrew Charleson said the students recommended demolition in many cases: "Probably about 25 per cent of heritage buildings were selected for demolition, mainly because of very limited heritage value and the poor state of maintenance."
Shape of our future
Likely features of new buildings:
* Lead rubber bearings as at Christchurch Women's Hospital, Parliament and Te Papa museum.
* Stiffer and stronger, resulting in less damage and fewer collapses.
* Seismic strengthening elements exposed to reassure building users.
* Energy-absorbing ductile beam hinges.
* Buildings spaced further apart so one building does not disturb another.
Likely features of older buildings:
* Brick masonry restrained by concrete or steel frames.
* Unreinforced masonry chimneys braced, strengthened or removed.
* Fewer concrete tile roofs and use more lightweight material such as steel.
* More timber frame construction or light-weight steel.
* Steel flues.
[Source: Institution of Professional Engineers NZ]By Anne Gibson @Anne Gibson Email Anne