Avoid Fencing Failures: Add Longevity & Dependability to Your Fence with Properly Installed Posts & Braces
It’s the phone call no livestock producer ever wants to get, the one that comes just as the family is sitting down for supper or heading out the door for church on a Sunday morning. “Your cows are out,” reports the voice on the line. “Need help getting them back in?” While a myriad of reasons might explain the escape, the most common culprit is fence failure. Whether they went over it, under it or through it, the cows found a weakness in the fence and exploited it. Now, they are someplace they shouldn’t be, potentially putting themselves in harm’s way.
“Sure, we’ve had cows out,” says Ben Hartwell, owner of Ben Fencin’, an agricultural fencing company in Gorham, Maine, who also runs his family’s cattle operation, Sebago Lake Ranch. “One time, I had used flexible posts and over time, the fence tension started pulling them down. I had a spot where it got close to the ground, and a cow stepped over it and got into the road. She didn’t get hurt, but it could have been avoided with better planning.”
Hartwell has built fences on a part-time and full-time basis since the mid-1990s and has learned through personal experience how to make fences that are dependable and long-lasting.
“Agricultural fences that are designed to be under tension are going to last longer,” he says. “They are a great fence, but they are only as good as their bracing.”
Properly designing brace assemblies and installing end and corner posts are keys to building a fence that will last a lifetime. But before you attempt to put the first post in the ground, Hartwell says you should take a closer look at the soil in which you’ll be working.
“The USDA’s Web Soil Survey has color-coded maps based on soil types showing how easy or hard it will be to put a fence in,” he says. “There are estimates of depth to bedrock and the general rockiness of the soil. It’s kind of like a suitability index.”
Once you have a better understanding of where a fence is to be built, Hartwell’s next piece of advice is to invest in quality posts. He recommends posts made from lodgepole or southern yellow pine that has been treated with chromated copper arsenate (CCA).
“Look for posts that have the American Wood Protection Association tag,” he adds. “I avoid red pine because it has concentric knots that create weak spots. I also avoid cutting my own posts, but if you plan to do that, make sure you treat the cut ends with a copper naphthenate preservative.”
Bracing assemblies vary in their construction, but the biggest mistake Hartwell sees is that people don’t set their corner, end and brace posts deep enough.
“Here in southern Maine, I like to go 3.5 to 4 feet deep to get below the frost line,” he says. “I also use a post that is 6 to 7 inches in diameter for my ends and corners, a little smaller for my brace posts. Anything less than 5 inches for a brace can actually slice through the soil when the fence is under tension.”
Hartwell prefers using a hydraulic post driver to set his posts. “A hydraulically driven post has up to 10 times the pull-out strength as a dug and tamped post,” he says. “If you’re digging holes with an auger or by hand, it’s critical that you when you backfill, you only pack a few inches at a time.”
By far, the most common bracing for end and corner posts is the “H” or horizontal brace. The brace has four different parts: the end or corner post being braced, the brace post, the horizontal cross brace that connects the two posts and the brace wire.
“The length of the cross brace should be twice to 2.5 times the height of the fence,” Hartwell says. “I like to place it just below my top wire. Tighten the brace with a diagonal wire that ties the top of the brace post to the bottom of the end or corner post. I use at least two wraps of high-tensile wire.”
A variation on the “H” brace is the “N” brace, in which the cross brace runs diagonally from the top of the corner post to the bottom of the brace post, with a bracing wire running in the opposite direction. Hartwell doesn’t use this configuration when he builds fences, but he says it’s popular with some. Because it’s angled, the cross brace in an “N” brace must be longer than in an “H” brace, which can increase the cost.
Though “H” braces afford optimum strength because they consist of two posts in the ground, it’s not always easy to accomplish, especially if you’re building in rocky soils. When just getting one post in the ground is a challenge, Hartwell likes to construct a “floating” brace.
This brace also consists of four parts: the post being braced, the brace itself, a brace wire and a brace pad. The assembly works by directing the tension of the fence down the brace into
“The most important thing with a floating brace is the angle of the brace,” Hartwell says. “You’re basically creating a 30-60-90 triangle with the post, brace and wire. The brace should be set at 30 degrees from the ground to the brace and 60 degrees from the post to the brace.”
For a brace pad, Hartwell says he uses either a flat rock or a patio stone; either will allow the brace to disperse pressure into the ground. It’s critical that the post be set deep, he adds, otherwise the fence tension will jack the post right out of the ground.
Another brace assembly that only requires setting one post is the “dead man’s” brace, which while not as strong as an “H” brace can also be effective. After setting a corner or end post, a 4-foot length of post is placed in a trench dug on the loaded side of the post, perpendicular to the fence. When the fence is tensioned, the force pushes on the “dead man,” which then pushes on 4 feet of soil.
“Some guys will also place a shorter block on the side of the post opposite the ‘dead man,’ to make it stronger,” Hartwell says. “The ‘dead man’ can act like a fulcrum when the fence pushes against it, and the block helps to prevent that.”
Gate openings need consideration as well. Posts may need to be of larger diameter and set deeper depending on the length and weight of the gate that will hang from it.
“If you’re hanging a long heavy-gauge steel gate, you might want a 9-inch diameter post,” Hartwell says. “But if it’s going to be a bungy gate or a multi-strand electric gate, I don’t do anything special for the bracing.” Hartwell shares one last piece of advice: Before you start installing permanent internal fences, use temporary ones for a few years.
“Once you find those places where you keep putting fence up and leaving it, that’s where you build permanent,” he says. “You don’t want to put in a permanent fence and then realize it’s in the wrong place. It’s too expensive.”
Find out more about Ben Fencin’ here.