EQ proofing for your house

When Christchurch was struck with a 7.1 magnitude earthquake in September 2010, there was a lot of damage caused by chimneys and hot water cylinders (HWC) when the houses were otherwise OK.

Why were these two items so destructive? Firstly, they weigh a lot. A 180lt HWC weighs around 200kg. That's as heavy as two rugby players. You wouldn't want them charging down the hallway at you, particularly when you are none too steady on your feet. I am sure you don't need me to explain what damage a chimney stack of bricks would do if it landed on your foot, or your head.

Secondly, they are made of different materials to the rest of the house. Most houses are wood, and have some flexibility in a quake. Bricks and metal cylinders are less flexible, so they get out of sync with the waves of an earthquake and pull loose of where ever they are supposed to be, relative to the rest of the structure. Out of place means causing trouble.

Thirdly, chimneys stick out a long way. They need to in order to do their job, but this also has the effect of leveraging the motion of the quake, and the further something is from the ground, the more it sways. Again, recipe for disaster.

A lot of this damage was preventable by simply strapping these items to the framing of the house to prevent them going their own way when the urge strikes. If you have a new HWC put in, your plumber should give it suitable seismic restraints. In my own house, the former owner has also secured it with a frame of wood around its base so it can't hop away. This is great, because not only will the HWC remain where it is, the water will be available for drinking if the main is disconnected.

If you have a brick chimney on your house or rental property, also get it strapped and secured in at least 2 directions. At worst, you'll never need it. At best, you'll save damage to your property, and maybe even save someones life. It is a pro-active insurance policy. Your regular insurance can't promise quite the same protection, so sort it out now.

Remember, Christchurch did not expect a 7.1 magnitude quake in September 2010, and it certainly did not expect a 6.3 in February 2011 as it was a fairly earthquake free region. If it can happen there, it can happen anywhere. Get prepared.