Fences are sometimes needed to heighten or reinforce a wall. Situations may include:
- A change in the type of stock, resulting in the wall no longer being effective.
- The need to discourage feral animals, such as deer and goats, from jumping into fields.
- A lack of stone may have forced the original builder to include a wall top fence.
- Lack of time or labour to repair a dilapidated wall may require a temporary wall side fence to be erected.
- The need to discourage people from climbing over the wall.
Where walls were designed to be topped with a fence, the posts were usually set into the wall, or less frequently, attached to the side of the wall. The wall and fence shown, near Ambleside in Cumbria, has wooden posts set in special long ‘through stones’ which have holes cut in them.
Because of the difficulty of adding wall-top fences, walls are usually heightened by using tall posts next to the wall. This method is not entirely satisfactory, as the ground is often too stony to knock in posts, which have to be leant against the wall. The use of materials is inefficient, as only the top part of the posts are used to support the wires.
Temporary or permanent electric fencing (Chapter 8 – Electric fencing) may be a more efficient and less unsightly method of stock proofing a wall.
Materials
Posts
Metal posts or standards are usually used for wall-top or ‘jump’ fences. This is because they are durable, and have a small cross section for their strength, making them easier to fit in the wall top than a bulky wooden post. A suitable type is a flat mild steel bar, drilled to take the required number of strands. Suitable sizes of bar are 5mm thick, and either 25 (1″) or 40mm (11/2″) wide, depending on the use and the length of wire to be supported. This can be bought from steel stockholders in about 6m lengths, and then cut to the required lengths and drilled. For maximum durability, the bars should then be taken to a galvaniser for treatment. Other materials can be used as available, particularly of salvaged material. Angle iron is strong, though rather unsightly.
Depending on the length of fence and the type of wire used, adequate straining posts must be included. These are a smaller version of a normal straining post, and can be made out of flat steel bar, with the top of the strut bent and bolted to the strainer. The larger size given above, 40 x 20mm (11/2 x 3/4″) should be used, or angle iron, preferably of the size 50 x 50 x 6mm (2 x 2 x 1/4″). The wire can be terminated at the straining post with eye-bolts, which are neat and allow for re-tensioning.
An alternative arrangement is to use a full height post set in the ground at a wall end or gateway. Provided a good sized post is used, and it is set sufficiently into the ground, no strut should be necessary as the wall end will provide support.
Wire
The best type of wire for jump fencing is high tensile wire, as this allows maximum spacing of intermediates, so reducing material and erection costs. This requires strong strainers and turning posts, and a wall that has long straight sections. Otherwise, use a 4.00mm mild steel wire and eye-bolts or radisseurs to permit re-tensioning.
Spacing of the wires will depend on the situation, the wall height and the use. Traditionally the top wire is about 450mm (18″) from the top of the wall coping, and spacings as shown above should be suitable for most uses.
Barbed wire should only be used on wall top fencing to discourage people from climbing over, as it will be no discouragement to stock. Similarly, electrified wires are no advantage, as the animals will be on or over the wall before they discover the wire is electrified. If using electric fencing, erect a scare wire instead.
An alternative method is to use stock netting for wall tops. Mild steel and high tensile wall top netting is available from several suppliers. Stock netting can be attached to metal straining posts by twisting or by fence connectors, and to metal intermediates with lengths of wire. Use 2.50mm high tensile or mild steel wire, as thicker wire is difficult to twist neatly.
Fence types
Jump fence
If the fence is constructed as part of a new wall, or one being rebuilt, the standards can be set in as the wall is built. The traditional method is to set the base of the standard in a hole cut in a through stone. This can be done using a cold chisel and lump hammer, making a quarter turn with each blow.
Another method is to rest the base of the standard on a through stone and mortar it in position, propping it in position as necessary until the mortar is set. A more secure fixing will be made if the base of the standards is cut as shown.
A quicker variation of this is to prepare hollow concrete blocks with posts set in mortar. These are then built into the wall so that the blocks are hidden.
If the wall needs to be stock proof from one side only, set the posts to that side to prevent stock jumping onto the wall.
Cornish hedges or stone faced banks, which are earth filled, can be heightened by knocking in wooden stakes and building a normal strained wire fence. Further details of walling are given in Dry Stone Walling.
‘Flying’ fence
Before deciding on the design, consider the following:
- Can posts easily be knocked into the ground beside the wall? Try a few trial posts.
- Does the fence need to be stock proof from both sides?
If the posts can be knocked in and only one side needs to be stock proof, the fence can be built as a normal stock fence, with the netting attached at the required height.
The fence posts can be thinner and set further apart than for a standard stock fence, as the fence does not come under the same pressure as a fence at ground level. Posts of 2.1m (7′) height and 50-75mm (2-3″) top diameter are suitable, set at 3-3.6m (10-12′) intervals.
Overlap the fence below the wall top as shown, so there is no risk of a gap being forced if the wire loses tension. If necessary, attach a strand of barbed wire 50-100mm (2-4″) below the netting to block any gap and discourage sheep from pushing through if they get up on top of the wall.
Turning posts at inside corners will need to be either tied back with wire (see below), or alternatively to have a strut fitted on the stock side. Keep the strut low to discourage animals rubbing on it.
Where posts cannot be knocked into the ground, you may have to tie them through the wall with wire. With most walls, wires can only be put in position as the wall is built, as it is not possible to thread wires through a double thickness wall. Use a loop of wire, and tighten it with a batten as shown.
To protect a wall from both sides, the posts can be set alternately on either side, and either knocked in or tied to the wall. Because of the zig-zag line made by the posts, if netting is used it can only be attached to alternate posts. On the other side, one or two line wires are attached to discourage animals from jumping up. This solution is expensive in materials, as long posts are needed, and you are effectively making two fences for the same boundary.
