Tips for Building Fences in Difficult Terrain
By Heather Smith Thomas
Building a good permanent fence can be challenging in rocky, frozen or swampy ground when it’s impossible to dig post holes efficiently, or set posts with a tractor-mounted post-pounder. Regardless of the type of fence, it will only be effective and durable if posts are well set. People who build a lot of fences have come up with innovative and effective ways to get the job done.
Fencing In Rocks
If terrain is too rocky to drive wood posts, metal T-posts are often used, since they are much smaller in diameter and can often be driven farther into rocky ground. If a person can get them down past the “shovel” portion, they are usually deep enough to hold.
If you need to set larger posts, like brace posts, in rocky ground, you might look for other options. A small rock drill is more portable than a jackhammer, since it doesn’t need compressed air. An electric drill can be used for drilling holes into concrete or breaking up concrete, and has various bits—including 1.5 inch chisel bits for drilling into solid rock. “This drill rotates and drills at the same time and can make a hole exactly the right size for a metal T post,” says Thomas.
In solid rock you only need to drill down about a foot and drop the metal post into the hole and it is tight and secure because there’s no give in the surrounding rock. For a brace post you can make a deeper hole using extra-long bits that can go down about 30 inches.
In rocky terrain where it’s not too steep and there are lots of surface rocks, you can create an above-ground basket/cage of rocks as a brace to anchor the fence. “Stacked rocks can be secured with net wire, or you can make a net-wire cage to put rocks in. A cage 3 to 4 feet in diameter makes a solid anchor to secure your wire and stretch it from there. If terrain is too rocky to set wood posts, you can usually put steel posts into the ground deep enough to hold, using rock baskets every so often for braces,” says Thomas.
Pilot Post
When using a post pounder to set wood posts along a challenging fence-line you can use a metal “post” to create a pilot hole. The metal post will often go down through rocky ground if it’s not solid bedrock, whereas a wood post would be forced out of line or shatter. Roger Swanson, a rancher in Lemhi County, Idaho, many years ago created a 7-foot metal pilot post, 3 inches in diameter. This can be driven into the ground with a post-pounder, creating a hole to start the wood post into. The pilot post is solid enough that you can drive it into just about anything but solid rock.
Thomas has made several of these for his own use. “A person can drive that pilot post down as far as possible, then pull it out with a tractor or skid steer loader. Then, you can insert a wood post into the pilot hole and drive it—forcing it into the slightly smaller hole—and the post will be very solid and secure,” says Thomas.
Pipe Posts
Some people use pipe posts; oilfield drill-steel pipe is great for making braces in rough terrain and won’t burn up in a wildfire. In western regions, fires destroy many wood fences, but pipe fences are still standing; the pipe posts will last more than 50 years. A person might have to replace the wire if a really hot fire goes through and makes it brittle, but the pipe posts will still be there and won’t have to be replaced.
Dick Iversen (Timber Creek Ranch, near Culbertson, Montana) has had a lot of experience building fences and hiring fence builders. “We had a huge flood in 2011 and had to replace 7 miles of fence on our river bottom. Then we had a fire during the summer of 2017 and had to replace 6 miles of fence between us and the neighboring ranch, in rough terrain,” he says.
For permanent fences he now prefers posts created from oil field drill-steel pipe. “This is great for making braces.” Oil field pipe is surplus and usually reasonable in price and is easy to cut with an electric hand-held band saw. “If I’m cutting pipe in a place where there’s no electricity, I use a little portable Honda generator,” says Iversen.
“Once a pipe post is in the ground, the ground tends to rust it to the soil around it, and it’s very solid. It’s very difficult to pull it back out. These posts work really well for corrals,” he says.
Todd Hermanson (Hermanson Fencing Company, Inc.) built Iversen’s new fences. Hermanson has been building custom fences for 40 years, in three states. He used to do traditional fences with wood and steel posts, but now does mostly pipe fencing, using discarded drill steel piping from the oil drilling industry. With a jack-hammer type hydraulic post pounder that he invented, he can pound pipe posts into any kind of terrain—solid rock, frozen ground, or bogs.
“This kind of fencing started with us. We took Bobcat hydraulic cement breakers and modified them to use for pounding posts. It was trial and error, but I have a guy in my shop who is good at making things. We came up with a system to do this kind of fencing—and it has caught on like crazy,” Hermanson says.
“The only thing that might shorten the life of these posts would be alkali ground that tends to eat up metal. It takes 2 minutes to pound another pipe post in. Even when repairing fence, if there is a broken off or rotted-off railroad tie, we don’t have to dig it out; we just pound a pipe post right down through the middle of it. This saves a lot of time,” says Hermanson.
In difficult terrain, this system is equal to none. “When we put fences across creeks or gullies. It’s very cost efficient and will be there a long time.” The pipe holds much better in places where it would be hard to brace with wood posts or the traditional steel posts.
The pipes are much stronger, and take less time to install. “You can put in a pipe brace, with the right equipment, in 10 to 15 minutes, which makes it a lot cheaper; a double H brace with wood posts or railroad ties takes more than an hour, and even longer to install in rocky or frozen ground,” Iversen says.
Steep Terrain
On steep slopes that are risky for a tractor, often a person can use a pounder mounted on a skid steer or a track machine, since it has better stability than a tractor and can go up relatively steep slopes without tipping over. Some people walk beside a track machine and drive it from the ground with a joy stick; you don’t have to be on it to drive it. This is safer, especially going through areas where it’s too steep to take any kind of vehicle or tractor.
This is handy for one person fencing alone because you can drive it as you walk beside it, and stop it where you want to set a post. This can save time and labor and one person can set a lot of posts.
Bogs And Swamps
Metal posts can often work when a fence has to go through wet areas and sloughs where it would be difficult to drive wood posts. If a bog is not too deep, you can use 7-foot T-posts that go far enough down to hit solid ground where they could hold. In some situations where the bog is too deep to hold posts, a person can build an above-ground jack fence. Building any kind of fence across a bog is often best accomplished in a dry season, or in winter when the bog is frozen, so you can get around in that area with a machine to set posts, without sinking into the mud.
Frozen Ground
Winter is not the best time to build fences that require posts set in the ground, but sometimes a person has no choice. There are times a fence must be repaired or a new fence built, regardless of the weather. Frozen ground can be challenging for setting posts, and cold weather is hard on machinery.
In cold weather, some people set metal posts instead of wood posts, since wood posts tend to shatter if the ground is solidly frozen. “With a jack-hammer hydraulic post pounder, however, a person can usually pound wood posts through a foot or more of frost (especially if a pilot post is used to start the hole) and then go on down to desired depth, and pipe posts will go even deeper,” says Thomas.
If frost is too deep for driving posts, fire is a common way to thaw ground for post holes.
“Old metal tubs or half barrels work well to make these little ovens. A cutting torch can be utilized to create small vent holes along the bottom edge (to draw air in, to keep the fire going) and a 5-inch-diameter hole in the top of each oven for the smoke to come out,” says Thomas. Fires can be set under several ovens, on the spots where you need to dig a hole or drive a post, letting them burn while working on other parts of the fence, and the ground underneath may be thawed within a few hours. In places where frost is really deep, scoop out the embers after the fire dies down, dig down through the thawed dirt, put the embers or coals back in, and add more wood.
Another method is to use hot water. One fence builder who had to set posts for a feedlot on frozen ground used a pressure washer with hot water, sticking the wand into the ground at those spots, slowly melting the frost down to the depth needed for setting posts. It was faster than fire, but still time-consuming for the hot water to melt its way down that far through the ice.
Above-Ground Fence
Another alternative in terrain that’s difficult or impossible to set posts is a jack fence (buck fence) or worm fence. A worm fence is created by stacking logs or large-diameter poles on one another, interlocking in two directions. The finished fence is a continual series of corners/angles. A short, small-diameter pole or short board is nailed or screwed to the logs/poles at the corners, to keep them stable so they will never shift around.
A pole jack fence (poles nailed/screwed onto jack legs) works well where ground is too rocky or boggy to set posts, but in windy country must be anchored so it won’t blow over. Fence jacks should be treated on the bottom end of those posts, to keep them from rotting. They will draw moisture, especially if built over swampy ground.
Portable Fencing
Temporary fences in winter or on rocky ground can be created with portable metal panels that interlock and don’t require posts. Portable corrals also have this advantage.
Portable electric fence can be installed with step-in posts, even if the ground is frozen, inserted into holes made with a cordless, battery-powered drill. For this type of fence it’s usually best to use portable posts made of metal rods, rather than the plastic step-in posts because the metal ones are less apt to break. You can add screw-on insulators to the rebar after you pound those in.
