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Earthquake resistance

Buildings which have a foundation system consisting solely of poles or timber stumps often have little or no lateral support to help them resist earthquake forces and transfer wind loads on the walls and roof to the ground. Lateral support can provided by diagonal timber braces or by more deeply embedding a number of stumps into the ground. The number depends on the size of the house and the earthquake or wind zone it is located in.

Buildings with a perimeter concrete or concrete block foundation wall, which have the framing above fixed to the wall with bolts or dowels, may not need stumps to have lateral support as the foundation walls could suffice. An architect, engineer or draughtsperson should be asked to calculate the bracing needed and advise on its installation.

There may be no obvious symptoms of a lack of lateral support to stump foundations. Where the framing is connected to the foundation wall with wires some extra form of lateral support could be needed.

Before

Modern science cannot yet predicr earthquakes. In Australia they are not common, although few have been of enough magnitude to cause damage. The following precautions can be taken in earthquake zones defined to reduce the risk of damage to your home and contents should an earthquake occur:

·   Ensure the hot water heater and any header tanks are properly restrained.

·   Ensure solid fuel stoves are anchored to hearths/ fireplaces

·   Restrain bookshelves and cabinets by having them fixed to the walls.

·   Have positive catches on cupboard doors to keep goods in them

·   Provide lips to the front edges of shelves so books, food, etc stay in place.

·   Ensure concrete and clay roof tiles are securely fixed to battens

·   Use Velcro patches to secure breakable items such as ornaments to shelves or walls

·   Store heavy items at low levels

·   Have chimney and gable end walls checked for structural adequacy by a builder or engineer. Repair if not adequately tied to the structure.

After

Following an earthquake it is wise to check you home and its surroundings for damage. The check should be carried out only when it is considered safe to do so and should include identifying.

·   New cracks in chimneys, foundation walls, brick or render finishes.

·   Leans, bulges or tilting of the building and retaining walls.

·   Any lateral movement of the building on its foundations or floor slab.

·   Misaligned door and window jambs

·   Ground cracks

·   Dislodged roofing tiles

·   Damaged sub-floor braces or bearers

·   Damaged roof space braces or rafters

·   Lateral movement of solid fuel stoves

·   Relative movement e.g. downpipes offset from drains

·   Damaged water storage tanks