If you're thinking about adding on to your home - a room, an out building or a patio cover, you need to know about metal framing connectors. They are special devices that provide added strength at wood connections where nails alone would not be sufficient.
Although metal connectors commonly are used throughout the country in wood-frame construction, they have a special value in areas where earthquakes, hurricanes and tornadoes occur. Structural integrity is only part of the picture. In patio-cover construction, for example, connectors that help attach posts to beams reduce the chances of both from twisting. They do this by simply holding the wood in place as it dries out. Wood tends to change shape when doing so.
Believe it or not, every type of wood connection can be joined with a metal connector of one kind or another. Connectors come in all shapes and sizes and range in thickness from very thin and lightweight, stamped or punched-sheetmetal units to heavy-gauge forged steel units. By the way, with metal connectors, bigger is better.
Connectors can be broken down into two basic categories: hangers and ties. Both are used to create stronger connections, but hangers have the added advantage of holding floor and ceiling framing up where a post or wall support would be impractical. Hangers are used to support the end of a horizontal framing member from its underside as when a deck is built onto the back of a house (where the rear wall is used as the support for one end of the deck framing). First, a board known as a ledger is nailed onto the house. Next, joist hangers are nailed onto the ledger. Finally, each deck joist is placed into the pocket of a joist hanger at one end, with the other end placed on a support beam.
When they're little they call them joist hangers; the bigger ones are referred to as beam hangers.
Nails are great, but a plain vanilla nailed connection can be pulled apart rather easily. And although it is true that a connection made with a metal connector can be pulled apart, it takes far more force to separate it than a simple nailed connection requires. End-nailing is where wood connections are most vulnerable and where metal connectors are most important.
If this all sounds too technical, maybe we offer some practical reasoning as to why metal connectors make sense. First, in an earthquake it has been found that the earth's movement causes the house to be thrown upward from the foundation. By the time the house begins to fall back toward the earth the foundation moves sideways and the house plummets off the foundation and onto the ground. With positive connections between the house and the foundation, the house would not leave its concrete support and, therefore, would stand less chance of being thrown off of it.
A similar principle is true with hurricanes. It is important that windows be kept closed in a hurricane. Air pressure traveling through the window and into the home can lift the roof right off the house. Keeping windows closed can create negative pressure inside and help to hold the roof in place. But proper nailing and keeping windows closed aren't enough in many cases. With only nailed connections, a roof could be blown clean away. Using metal connectors to attach each roof framing member to the wall that supports it makes for a more positive connection. And if heavy winds occur, there is a better chance that all will stay in place.
It should be noted that special nails are used to install joist hangers. They are called - and very appropriately so, we might add - joist hanger nails. Since this type of connector is commonly cross-nailed into 1{-inch-thick boards, joist hanger nails are just under 1{ inches in length. And that's a good thing because you don't have to worry about driving a nail through your finger when you're installing a joist hanger.
