What are the Basics of Slabs on Grade?
The proper design and location of joints is an area of confusion throughout the construction industry. There are three types of joints: • Isolation Joint – Used to prevent a bond and allow movement between the slab and the adjoining structure. • Control Joint – Used to induce shrinkage cracking at specific locations. • Construction Joint – Used to provide a stopping place for a concrete pour. The construction joint can also be detailed to function as an isolation or control joint. The basic theory of joints must be understood in order to use the correct joint at the correct location. The isolation joint should be used to allow the concrete floor and the rest of the structure to act independently. There is not key way or bond of any type through an isolation joint, allowing movement both horizontally and vertically. The figure below illustrates a typical isolation joint detail and a plan of an isolation joint at a steel column. The isolation joint at a column is often in the diamond sha
