For some types of fencing, erecting a fence on a hill requires little or no change in construction methods. A rail fence or a barbed wire fence, for example, can follow the contours of a hill and retain a neatly organised appearance. However, this is not an option for fences which present wall-like barriers, such as privacy fences, chain-link fences and woven-wire fences. To follow a hill,you must erect all these fences using the stepped method.
Drive a stake with a rubber mallet at the crest of the hill. Drive in a second stake at the foot of the hill.
Loop the end of a line of string around the stake at the top of the hill and tie it off. Push this loop down to the bottom of the stake, so it meets the ground.
Run out that string downhill to the other stake. Loop and tie the string around the other stake. Place a carpenter's level atop the string and adjust it up or down the stake until the line is level.
Measure the space between the string and the ground at the bottom stake with a tape measure to determine how far the hill slope falls. This is the "drop" of the hill.
Measure the length of the slope by walking it with a measuring wheel. Divide this by the required space between your fence posts to determine how many fence posts you must set into the hill slope. That might be 5 feet for a privacy fence, 8 feet for a wire fence or 10 feet for a rail fence. If you must cover 150 feet with a privacy fence with 5-foot wide panels, you must set 30 posts.
Divide the "drop" of the hill by the number of fence posts to determine the "stepping" measurement for the fence, or the distance each section of the fence must rise or fall as it makes its way up or down the slope. If the "drop" is 6 feet and there are 30 posts on the slope, each section of fence must move 2.4 inches.
Subtract the "stepping" measurement from the depth of your post holes. Depending on the type of fence being built and whether the posts are to be set in concrete, post holes are typically between 1/3 and 1/2 the height of the posts. To compensate for the "stepping," however, the posts need to stand a little taller above the ground, so the post holes must be correspondingly shallower.
Dig post holes, set your posts and fasten your wires, panels or rails as normally dictated by the instructions for that particular type of fence, making the adjustments for post hole depth and "stepping" each section of the fence when you start building on the hill slope.
To build a contour fence, simply construct the fence as you normally would and arrange the rails or wires to follow the slopes of the hill by continuing to fasten the rails or wires to the same locations on every rail. As a result, the fence will rise or fall with the hill and at approximately the same gradient. On particularly steep slopes, it may be desirable to "step" a fence even if you could otherwise build it following the contour method. Hill slopes which are long or steep might pose measurement problems with ordinary wood or plastic stakes. To overcome this, either take your "drop" measurement in stages or use a long stake at the foot of the hill.