When building a boundary wall an expansion joint is a separation designed to relieve stress on building materials caused by movement induced by thermal expansion and contraction.
Brick wall expansion joint.
They are therefore specifically provided in boundary walls to avoid cracks occurring in the wall.
An expansion joint in brickwork and blockwork is a means of solving potential problems caused by movement.
Prime candidates for expansion joints include long expanses of walls corners offsets setbacks and parapets.
The expansion and contraction of masonry needs to be accommodated and controlled by the inclusion of both vertical and horizontal joints within the building.
This allowed movement helps prevent distortion and cracking.
Expansion joints must be located so that the structural integrity of the brickwork is not compromised.
Expansion control joints to control the expansion and protect the wall structure from cracking under pressure masons install vertical control joints at specific locations.
The joints are formed by leaving a continuous unobstructed opening through the brick wythe that may be filled with a highly compressible material.
The coefficient of expansion or e value of clay bricks when tested in accordance with as nzs 4456 11 can vary from a very low 0 3mm m millimetres per metre to over 1 6mm m.
This allows the joints to partially close as the brickwork expands.
Expansion joints should be located where stresses or cracks are likely to develop in brickwork.
Most general purpose bricks have a coefficient of expansion in the range 0 5 to 1 0mm m over 15 years.
This movement could be a result of thermal expansion moisture movement creep and structural loading or the effect of chemical changes.
Expansion joints should also be located below shelf angles to account for vertical expansion of brick.
These joints will absorb the pressure created by the expansion by giving the masonry wall flexible space to expand.
Brickwork showing wall ties spaced no more than 225mm from the expansion joint movements joints and their size vary depending on the size of the wall.
Clay brickwork will generally be subjected to long term expansion while concrete masonry aggregate blocks aircrete blocks will be prone to shrinkage.
Exterior vertical wall expansion joint selection guide emseal watertight fire rated sound proof insulating precompressed foam sealant expansion joints selection guide.