Q.: Regarding isolation joints, why does the industry still use thick expansion joint material? Are there other factors than just isolation? What about expansion in heated buildings? Can I safely use just building paper as an isolation joint, thereby reducing surface irregularity and cleanup problems around isolation joints or columns in warehouses?
A.: Thick expansion joint material is used as much as a matter of convenience as anything, to be certain that there is adequate separation between two elements. The main purpose is to isolate one element from another. Building paper can be used as an isolation joint in some circumstances such as a column located at the intersection of joints running at right angles in four directions, where there is likely to be no sliding action in the isolation joint. As far as actual expansion of concrete elements in the heated buildings is concerned, the expansion is never likely to be as large as the original drying shrinkage.