Joist hangers strengthen a floor because without them, there would be no floor to support. Floor joists are the lengths of 2-by-6-, 2-by-8- or 2-by-10-inch lumber. They run horizontally and provide the support for subflooring, flooring and everything that rest atop the floor. In other words, they provide support for weight that is focused solely downward. Floor joist hangers, in turn, support and enable floor joists to stay in place.
Joist hangers are metal fixtures that attach to horizontal beams and rims of a building’s frame. They provide a cradle for the joist to fit into. Each joist is supported by a hanger at either end. The joist hangers themselves are affixed to a beam or rim joist with tico nails, extra-wide nails designed for sheer weight. The joists are then affixed to the joist hangers with the same nails. Screws or 16d nails are never used.
Without joist hangers, joists would eventually give way under the weight. In some instances, joists are doubled or tripled and attached to a corresponding joist hanger to add even more support.
Source: www.DoItYourself.com
