Reducing the risk of earthquake damage
In the light of the 7.8 magnitude earthquake that devastated Kaikoura on 14 November and the associated aftershocks, which have been felt in many parts of the country, you may want to take this opportunity to remind your clients how they can earthquake-proof their homes.
BRANZ released the following guidance for builders and homeowners highlighting ways they could reduce damage to their homes during a shake after the 2010 and 2011 Christchurch earthquakes and is still relevant today.
To prepare a home to cope better in an earthquake, you can:
- Strap hot water cylinders at the top and bottom to the wall framing; if possible, have the cylinder on a concrete base.
- If you have a header tank, tie it securely to its base (roof space or on the roof); ensure the base is also securely fixed.
- Provide lateral (bracing) support to piles and subfloor jack framing.
- Ensure that piles are solid (replace rotted timber piles) and connections to bearers, such as wire ties or straps, are in place and secure.
- Ensure that concrete or clay roof tiles are tied or fixed to tile battens.
- Anchor solid fuel appliances by bolting to the hearth or through the floor.
- Secure a chimney to the structure and strengthen it; alternatively, remove the chimney.
Within the home:
- Ensure that cupboard doors have a positive latch to hold them closed.
- Fix bookshelves and cabinets to the wall with ‘L’ shaped brackets.
- Provide a lip to the front edges of shelves, so items are less likely to fall off.
- Store heavy items close to the floor.
BRANZ also said that, based on observations, most homes performed well, but there were exceptions where there was significant damage; these included:
- Houses with complex designs such as split-level design, irregular plan shapes, vertical irregularity or a mix of structural systems and stiffness.
- Houses with heavy elements such as walls of solid unreinforced masonry (brick or concrete block) or brick chimneys.
- Connection failures between structural and non-structural elements, to cladding attachments, and to the interface between original construction and more recent additions.
- Unreinforced concrete slabs on ground.
- Use of brittle steel reinforcing to foundations and slabs.