[craig1234564]

Out of interest what is the main reason for NZ houses being wooden with corrigated iron roofs? Is it because of earthquakes and high winds, so that the occupant would be less likely to get injured? :)
Or why not use bricks and slate roofs as in the UK?

[migratory birds]

Might have something to do with available resources - iron being more available than slate?

[BkyMonster]

I'd guess that a lack of brick housing other than a brick facade supported by timber would be due to the earthquakes. The western coast of the US doesn't have many brick buildings for just this reason.
Haven't a clue about the roofing though.

Have a look at a previous discussion :)
http://www.emigratenz.org/forum/archive/index.php/t-4384.html

[Super_BQ]

When I was looking to buy a house about 7+ years ago, I often questioned about the building methods and materials used to the real estate agent. She said the techniques and materials used were to withstand NZ's "rough?" environment. Regular 100+ km/hr winds, possible major earthquakes, etc.

Has anyone questioned about the cost? NZ is not the only place with strong winds and earthquakes.

Perhaps we need to question some of the historic landmark buildings. Even in commerical buildings where it's pretty much brick and concrete. I do love all the artwork put into laying those bricks in how they arched around the windows and walkway entrances. Perhaps we've not seen a big enough earthquake to rumble down all these historical places?

Your typical NZ state home does have slate/tiles (or what ever they call them - they're all made of mix of concrete / brick and glazed heated) for the roof. Certainly a lot heavier compared to iron roofing and not necessarily safer in a major earthquake. I havn't seen any of the tar shingle roofing in NZ. But then many will argue it's potential fire hazzard.

[BaldyBeardyBloke]

Most new houses in the UK are constructed the same way nowadays, except the roof. It's a speed thing, with pre-fabrication and minimisation of 'wet' trades being the key. Time is money as they say.

As for the roof's, I suspect cost/speed again, but safety from falling heavy objects is probably in the mix too.

[IanW99]

Did watch a program on houses a while ago and it showed that wooden framed houses (like most of NZ) are better able to withstand major earthquakes.

It also went on to show that in Japan where they have the same wooden frames, that they went for much heavier tiles on the roofs and found that heavy roofs caused the buildings to fail in earthquakes.

So, wooden houses with light roofs are the best way to go for the average home in NZ (or at least that was what was implied). I'm sure there is a financial reason as well :)

I think many of the historic buildings were built of brick before they realised the problems, many of these building have had to have earthquake protection added - see Te Papa or Parliament building for details of what they do (basically support the building so it floats on rubber bearings).

If you visit Porirua hospital museum, it shows the old Porirua hospital was made of brick but doesn't exist anymore because of an earthquake.

Ian

[Nick88]

I have a relative that is a builder and he told me that a third of the cost of a new house in the UK is due to the roof. The tiles and heavy duty trusses add a huge amount of cost. More than I expected. Plus there is the earthquake problem....

[ourquest]

Building materials will be chosen for many reasons, aesthetics, safety, availability, cost, efficiency (in no particular order).
Earthquakes have had a major influence on NZ's building. During an earthquake the ground can move considerably, so unless the building is suspended or articulated (to either isolate it, or allow parts of it to move relative to another, concrete highrise buidings in the cities will be built this way) then it must be flexible to accommodate movement. Bricks and mortar are brittle, so in a quake walls crack, and cease to be structurally sound. And of course if they collapse they are that much heavier (than wood), as well as forming a multitude of lethal bits that could easily kill someone if struck on the head, for example. The same argument holds for heavy roofs made from individual tiles. It also makes no structural sense to cap a flexible structure with a less flexible and heavy roof. During an earthquake you want the weight lower down, otherwise the roof will literally pull the walls apart because of its inertia/momentum. And again, for safety, you wouldn't want the roof to fall on you, either as a whole or in bits.
The possibility of serious earthquake in NZ is very real. Napier was famously all but flattened around 1930...this is geologically speaking very recent. And if the possibility exists, then structures have to be built accordingly, otherwise the toll should an earthquake hit be devastating. It's all about risk. New Zealand is zoned according to risk, and so regionally there might be some differences in building method.
For a simulated earthquake experience (which is probably a poor representation of the real fear and danger, but gives some insight) then Te Papa museum in Wellington has a simulator, and so does the Volcanic Activity Centre between Rotorua and Taupo. These venues also provide free brochures with hints to earthquake proof your home...this includes fixing heavy ornaments to shelves, strapping geysers in place and other things you may not have thought of.
Natural disasters happen when people are not expecting them. But geologists have a good understanding and a well developed hazard mapping approach to identify measured risk for various regions.
You might also think twice about buying that dream home right next to the sea. Given the choice I would invest my own money in one that is at least 35m above sea level. Global warming might give you lots of warning, but tsunamis don't possess that characteristic. And where there is a risk of earthquake, there is a risk of tsunami.

[markw55]

Also, a lot of NZ houses are quite old and made of wood. Traditionally wood has been a cheap material to find in NZ.

It was so cheap and plentiful that in early 1900s - 1940s houses were almost all built out of lovely native timbers (which is why old villa and bunglows have a premium price).

Now days lots of new houses are built with different materials.

And then there is the fact that wood moves when the ground shakes and brick cracks.