People often ask about the difference between a floor construction joint and a structural expansion joint. Engineers design expansion joints when physical gaps in concrete slabs are designed to accommodate building movement. These joints generally accommodate substantial movement, starting at around 5mm and going up to 50mm. Kirk refers to these gaps as “structural expansion joints”.
Floor construction joints and control joints are vital to ensuring that any cracking that might occur after the concrete slabs have been poured can be controlled, instead of this occurring at random. Control joints are cut into a grid spacing over large spans of slab and these control joints allow the slab to accommodate shrinking, thermal fluctuations and loading.
Concrete slabs that have been tiled and screeded require movement joints to be placed on grids that are similar to the control joints. These grids are generally around 5m x 5m but can vary depending on the slab design. These movement joints accommodate small movements to prevent tiles and screeds from cracking.
Movement joints are manufactured in aluminium, brass and stainless steel, enabling them to absorb 20% of the width of the joint movement. Kirk’s infills have excellent hydrolysis, good abrasion, chemical resistance and physical properties. Kirk recommends using a movement joint instead of a soft joint option because the soft joint is not long lasting and will have to be replaced a few times during its lifetime.
For more information, contact Kirk on +27 (11) 444 1441 or via www.kirk.co.za.
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