What is a Plumb

Definition of Plumb in Construction

The term plumb is used to indicate a vertical accuracy, that places the construction element at right angles to the horizontal position of the floor slab, the ceiling, or any other surface that is horizontal. Specific tools are used to identify whether an item is plumb. One of these tools is called a plumb bob, which is basically a free hanging weight, which is shaped to allow the center of gravity to align with the center of the weight. By tying a string to the end of the weight, it will hang vertical, or plumb, based upon the gravity pull of the earth. Another tool that is used is a level. A level is an enclosed tube that has a bubble of fluid that shifts to the center of the tube, when the level is either plumb (vertically) or level (horizontally) aligned. In most construction projects, the structure supporting the building loads is required to be plumb, to ensure that the load axis is at the center of the loads, being applied to the structural element. When a load is applied directly plumb, then the load is applying a vertical load vector (force) on the supporting structural element. If a structural element is not plumb, there are various other force vectors that are being applied to the supporting members of the load. These other force vectors can cause twisting, lateral movement, moments or other negative type loading conditions, which are not structurally correct. Vertically plumb structural elements are extremely important to the proper structural function of a building, or other construction assembly.