During the construction of a monolithic structure it is advised for the work to be carried out continuously. However, this is often not possible. In such a case one is forced to use construction joints (or day joints). Construction joints in monolithic structures are areas of contact between hardened concrete and freshly poured concrete. Despite the fact that construction joints are invisible in the structure, they are usually weak points. Hence, they should be located at spots where any joint between hardened and freshly poured concrete has no material influence on the structure's safety. Such spots may not be found where the strongest bending moments are, and they may not be in hard-to-reach areas.
Within ceiling slabs, as well as in concrete beams, a construction joint is recommended at a distance of about 1,5- or 1,4-fold of the span of the slab as measured from its support. In components, where large compression forces will emerge, the construction joints should be executed as perpendicular to the direction of these forces.