Travel any country road, and you’ll see plenty of fences with sagging wires or mesh so loose that all but the most timid livestock will laugh at them. Focus on the corners, and you find posts that appear to rise miraculously out of the ground, tilting precariously. Fence failures such as these are commonplace, but most of those sagging wires are caused by an anchor (corner or end) post being pulled from the ground by the tension of the wires themselves.
Well-braced fence ends and corners aren’t rocket science, but you need to consider a little physics, or follow the advice of experts, to get them right. And sometimes 6 inches make all the difference between a lifelong fence installation and one that fails in a few years.
Why bother with braces?
The typical tensioned-wire fence exerts a minimum of 1,000 to 1,500 pounds of pull on an anchor post. Likewise an anchor post serving as a corner post must withstand that much pull in two directions. Soil movement due to temperature and moisture fluctuation, and livestock or wildlife collisions with the wire can easily increase the pull to 2,500 pounds or more.
Obviously, the magnitude of these loads is more than an average post can bear for any extended period, but, with a bit of thoughtfully placed bracing, a 6-inch-diameter wooden end post will offer an anchor capable of withstanding temporary pulling loads up to about 6,000 pounds.
A brace by any other name …
Many brace styles have been used successfully around the world. A few rely on an earth anchor or deadman (such as a large rock or log) buried in the ground and wired to the anchor post opposite the pull imposed by the fence. While these are inexpensive and easy to install, they are not effective when the fence follows or ends on property lines because they extend outside the enclosed area (they are also easy to trip on, catch mowers and injure livestock).
Other brace styles use a combination of vertical posts, horizontal or diagonal rails and wire to help anchor the fence. These are installed in the fence line between ends or corners, so they are perfect for perimeter fences that follow property lines.
In places where rocks are abundant and/or it is difficult to set posts at least 3 feet into the earth, a number of stone cairn or crib braces can be used – but they extend out of the fence line and might not be appropriate for property-line fences.
Single-post diagonal brace
Leave it to our friends in New Zealand to come up with an inline fence brace that’s attractive, relatively easy to build and offers economy of materials and labor. This so-called kiwi brace is strong enough to anchor a 660-foot-long fence made with up to six stretched wires without any line braces built into the fence’s interior. The brace employs a single 6-inch-diameter (or greater) anchor post set vertically into the ground a minimum of 36 inches (deeper is better) and a diagonal rail and slider block to keep it upright.
Once the anchor post is set, measure twice the height of your fence’s top wire from its base (down the fence line) and center a large smooth rock or concrete block on that point. This slider block will prevent the brace’s diagonal rail from digging into the ground and allows the anchor post to flex with soil temperature or moisture changes and when the fence experiences an impact.
Next, select a straight 5- or 6-inch-diameter post long enough to extend from the center of the slider block to just below top-wire height on the anchor post and cut the ends diagonally to match those surfaces.
Install this rail by attaching it at the post end with a 3/8-inch galvanized steel pin. Tension the brace by twisting (with a twist stick) a couple of wraps of 9-gauge brace wire looped (and stapled) around the base of the anchor post and the end of the rail about 3 inches above the slider block. If the rail has a tendency to move out of the fence line under tension, drive a stout stake on either side of it to keep centered.
Two-post horizontal brace
The two-post brace with a single horizontal rail is considered to be the easiest anchor to get right the first time. Like the kiwi brace, the two-post horizontal brace makes a good anchor for 660 feet of fence constructed with up to six tensioned wires.
This brace consists of a 6-inch-diameter (or greater) anchor post, a 4-inch-diameter rail and a 6-inch-diameter brace post. Drive or set the posts a minimum of 36 inches into the ground – spaced approximately twice the fence’s height from one another. Pin the trimmed rail between the posts just below the top wire (lower if the rail is shorter than twice the fence height, but never less than half the fence height from the ground).
Tension the brace by twisting a couple of wraps of 9-gauge brace wire looped (and stapled) from rail height on the brace post to about 3 inches above the ground on the anchor post. Don’t over-tension this brace or it will have a tendency to jack the anchor post out of its hole.
Rock crib brace
This anchor is often overlooked, even in places where there’s plenty of raw material. If you plan to use this brace on the property line, check with your neighbor(s) to be sure they don’t mind since they will need to use some of the same anchor posts that you do.
The rock crib brace consists of two or four posts and sufficient wire mesh to form a 4-foot-diameter crib at least 3 feet tall. For end braces, simply install a pair of 6-inch-diameter posts a minimum of 3 feet into the ground (if possible) spaced 4 feet apart. Place the wire mesh crib between the posts, wire the posts together with three evenly spaced loops of 9-gauge brace wire (these pass through the crib) and fill the crib with rocks.
Take some care with stacking the rocks to achieve the most stable brace. The most effective way to brace a corner this way is to set another pair of posts at right angles to the first.
Grit Editor Oscar “Hank” Will has constructed (and reconstructed) a few fences in his day on farms from South Dakota to New Hampshire. He’s currently working on a corral in Osage County, Kansas.
Hank Will raises hair sheep, heritage cattle and many varieties of open-pollinated corn with his wife, Karen, on their rural Osage County, Kansas farm. His home life is a perfect complement to his professional life as editor in chief at GRIT and Capper's Farmer magazines. Connect with him on Google+.