Maintenance and Construction of Exclosures

The information below is based primarily on FoNAF’s field experience during 2010.

Raising Exclosure Fences Efficiently

During 2010, FoNAF and the public (on our public workdays) repaired and raised the fence on more than 6 miles of exclosure perimeters.  We could achieve so much only because we developed methods that are more efficient than those that we inherited.  The innovations have been collected into an illustrated document entitled Raising Exclosure Fences Efficiently.  Click here to download a pdf file (2.7MB).  You are welcome to reproduce the document for use in the field.

Maintenance

Exclosures on the Flagstaff Ranger District usually fall into one of two classes.

  1. Two panels of woven wire.
  2. One panel of woven wire with one or two single strands of high-tensile wire both above and below the panel.

I will first describe raising the fence on the two-panel class. Then the other class will require only a few additional comments.

Two panel fence

  • Big picture: lift the fence as high as you can while limiting the gap at the bottom to six inches or less.
  • Unclip the panels from existing T-posts (and from trees, if readily possible). If the two panels overlap, unclip the panels from each other.
  • Place the top of the fence seven feet off the ground. Hold the wire up with one or more stays that have a tilted staple at the 7' mark.
  • Leave no gap between the two panels of woven wire. Connect the two panels with hog rings at intervals of three feet or so.
  • At the bottom, aim for a gap of no more than six inches. (Apparently, a gap as wide as 12 inches is sometimes OK.) Fill in hollows with segments of dead aspen or stretch a wire.
  • Remember that only the top and bottom wires of the woven wire are “load bearing” wires. Nonetheless, apply a fence clip to at least one intermediate wire to help support the mesh when it is loaded with heavy snow.
  • Insert 8' wooden stays liberally. Thread each stay through each panel of woven wire so that two wires are on your side where the vertical spacing is large and three wires are on your side where the spacing is narrow. (The load-bearing wires are always on your side.) Attach the load bearing wires to the wooden stay with U-clips and screws.
  • Insert new 10' T-posts as needed only. Where the interval between existing 8' T-posts is 20', it may be necessary to insert a 10' T-post at intervals of 40 or 60 feet (between adjacent 8' 1 Last revised on 12 December 2010 posts). Then place wooden stays between the remaining 8' posts. Obviously, many variations on this pattern are possible. That’s especially so if FoNAF finds a good way to extend an existing 8' post to be effectively a 10' post.
  • Fixing breaks. Best to use woven wire. Extend two feet (or 30") beyond the break on both sides. Often useful to run the woven wire vertically.
  • If vertical wires have come undone from the top load-bearing wire, wrap the vertical wires around the load-bearing wire before re-attaching it to the T-post.
  • Over-head wires. In soft ground, T-posts will sink and will carry the woven wire with them into the ground. Extricating the woven wire (in order to raise the fence) may consume so much time and energy that the effort is not worthwhile. In that case, string one or two strands of high-tensile wire over the existing fence. Attach the wires to new stays or to 10' T- posts. Aim for a spacing of 6 to 8 inches—certainly no larger.

Single panel fence

  • Big picture: lift the fence as high as you can while limiting the gap at the very bottom to six inches or less.
  • Moreover, no gap below the single panel of woven wire should exceed 6" inches, and no gap above the panel should exceed 8".
  • The design goals just given will limit how high you can raise the top of the woven wire panel, given two wires below the panel and two wires above it. If the panel has a width of 4', the best you can do consists of putting the top of the panel at 5.5' and the topmost wire at 6' 10".
  • Use the heavier gauge wire for the top wire(s) and also the bottom wire(s). If you can bend the wire with your fingers, it’s the lighter gauge.
  • Reject the temptation to support the woven wire panel by hanging wires down from the upper single strands of wire. No engineer would take that route; the angles would be all against you. Rather, if the panel needs more support, use more wooden stays (and thus support the panel from the ground up).

New construction

  • Try hard to find a large, live tree for a corner post. (That is, avoid cobbling together a corner post from a T-post and braces or from an H-construction.)
  • Install 10' T-posts at intervals of 20 feet. This suggestion needs to be checked after a winter or two, for example, by checking on exclosure #12 (which was rebuilt with a 20' interval in May 2010). (Apache-Sitgreaves NF used an interval of 10 feet.)
  • Insert a wooden stay between adjacent T-posts.
  • FoNAF’s stretcher clamp works well. Wing nuts suffice. Using a wooden stretcher clamp keeps the woven wire in good, undistorted shape. The FS rig with three hooks distorts the mesh badly. (The FS rig was designed, I believe, for stretching chain-link fence, which has more and thicker wires.) Take the trouble to do the job right.
  • Use the “wire jenny” to unwind the wire from a large coil of wire.
  • Using staples. Small pines: OK to use staples. Large pines: apply several wooden 2 by 2s and wrap with wire; staple into the 2 by 2s—and also into the tree, if needed, but sparingly.
  • Note that FoNAF has 3" stainless steel screws that can be used with U-clips to attach load- bearing wires to trees or to stays-on-trees. The screw and U-clip system works better than does a staple. Even a 3" galvanized iron nail and a U-clip work better than a staple.
  • Roll of low-carbon woven wire. Bekaert 1047-6 12.5g Low Carbon Field Fence. 330 feet long. 47 inches wide. Top & bottom wires: 10g. Line wires: 12.5g. This is the wire we used on the north side of exclosure #12 in May 2010 (for the lower of two panels). Approximate cost: $200 per roll, equivalent to 60 cents per linear foot.
  • That’s the older wire. Modern wire has a higher carbon content and provides the same strength with less iron. Consequently, it costs less per linear foot. Also, the modern wire sags less and is more resilient (after a tree falls on it). Look into the newer wire before buying any woven wire. (Bekaert’s brand name for such wire is “Gaucho.”)

Notes by Ralph Baierlein, with assistance from Dave Downes and Dave Laplander.