What are Movement Joints?
A movement joint refers to a joint between two adjacent surfaces subject to move through joint expansion and/or contraction. The degree of joint movement depends not just upon the two visible surface materials seen to form the joint, but also upon the materials used to support those surface materials and the particular construction methods employed in the building process.
In the drying out process, the loss of moisture causes many materials to shrink and the perimeter joints to expand. This joint expansion must be considered prior to construction. If provision is not made for such materials to contract, gaps will appear and such joints will not remain watertight.
The absorption of heat and moisture causes many materials to expand and the perimeter joints to contract. If provision is not made for such materials to expand, ‘bulging’ will occur.
Movement joints are specified throughout construction to relieve tension stress where materials may contract and compression stress where materials may expand. Movement joints are also specified as a means of partitioning areas to avoid the effects of differential load settlement leading to stress fracture ‘cracking’ in walls and floors.