By providing vertical support to floor joists in a building frame, joist hangers enable a floor to support the sheer weight it is exposed to. Without them, joists would be forced to support the weight with only nails set at 45 degrees. Joist hangers provide a cradle for the joist to sit in. Special nails secure both the joist hanger to the beam or rim and the joist to the joist hanger. Most joist hangers used in residential construction are equipped to hold 2x6-inch joists. Sometimes, however, bigger joist hangers are required to doubled or tripled joists.
How Joist Hangers Work
Joist hangers attach to the structural beams of the frame. There are two, one at either end of each joist. They are machined out of metal and provide a lower edge or cradle in which the joist sits. Some joist hangers have an upper flange that hooks onto the beam. Most residential joist hangers do not. They come with pre-made holes so you can easily drive nails into them. Once the top of a joist is flush with the beam, you nail the joist hanger into place with weight-bearing nails. When both hangers are in place, you set the joist in and secure it with the same nails placed at 45-degree angles.
Single Joist Hangers
Most joists used to make the flooring of a typical residential home or structure require single joist hangers. The distance the joists must span is not that great, and the load they must bear is shared by all of the floor joists in a given room. Most floor joists consist of 2x6-inch lumber, but they can use 2x8 or 2x10 as well, which will require longer joist hangers.
Double and Triple Joist Hangers
Double and triple joist hangers are wider to accommodate either a thicker piece of lumber or two or three joists placed side by side. In these cases, the joist hangers will be 4x6 inches, 6x6, or 6x8, depending on the dimensions of the joists. Rim joists are thicker lengths of lumber used at the edges of a home’s frame. They are at least 4 inches wide and require a double joist hanger.
In areas of a frame where joists are forced to span a wider distance, joists will be doubled or even tripled to provide more support.
Joist hangers are an integral part of a building frame. In some cases, it becomes necessary to place two or more joists side by side to add more vertical support or to support a large piece of horizontal lumber such as a rim joist. When this need arises, you will need double or triple joist hangers. They are essentially the same as single joist hangers, just wider.