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2010 & 2011 CHRISTCHURCH EARTHQUAKES
In 2010 the city of Christchurch was hit by a 7.1 magnitude earthquake, five months later it was again hit by a 6.2. It was interesting to see how brick homes fared.
A post earthquake survey noted, many of the major masonry failings related to historical structural brick buildings, however more modern brick veneer houses generally performed well during the Christchurch earthquakes. The small amount of damage associated with brick veneer constructions was due to poor installation.
HOW ARE BRICK VENEERS ABLE TO STAND UP TO EARTHQUAKES?
The bond between brick and mortar is the most important single factor affecting brick veneer strength during a quake.
The bricklayers workmanship greatly effects the quality of this bond.
Mortar needs to be mixed to the proper strength. This should be at least 6MPa which can be achieved with a mortar mix of 4:1 sand to cement.
Many modern clay bricks are made with vertical core holes to reduce weight. When the mortar is mixed wet enough it should be able to flow into the core holes, creating strong mortar dowels that lock the brick course's together. The bricks need to placed quickly after the mortar bed is spread so that it doesn't become too dry.
Once a brick has been placed it should not be moved. Repositioning the brick will weaken the mortar seal. Recent building standards require brick ties to be screwed to the framing rather than nailed. This stops the bricks being disturbed from hammering vibrations.
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