Most prefabricated fence styles feature horizontal line wires joined to vertical picket wires via either a hinge, a ring, or wire knot. Because all line wires are run out together, prefabricated fencing offers considerable time saving during erection.
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There are two types of barbed wire available. These are the old 2.50mm Iowa pattern and the high tensile, either 1.57 or 1.80mm. The high tensile barbed wire can be used successfully in suspension fencing. It also offers considerable savings in freight being approximately half the weight of Iowa barbed wire.
Vertical picket wire spaces can be selected from 5cm, 15cm, 30cm, 45cm or 60cm, depending upon the type of stock to be contained and the particular fence type selected. Fence sizes are conveyed by the naming system e.g.: 6/70/30 means there are 6 lines wires, the height is 70 cm and there is a 30 cm space between verticals or pickets.
There are two types of plain wire, low (soft) and high tensile. High tensile wire does not mean high tension but refers to the chemical composition of the steel which allows a thinner wire to have the same or greater strength as the soft but thicker wire. High tensile wire is more elastic than low tensile (soft) wire because of its steel properties. This enables the wire to retain much more tension after movement of an end assembly and means that the periodic restraining of wire is not necessary. These inherent qualities allow longer strains, wider post spacings and suspension fencing - all cost saving factors. High tensile wire whilst having the same or more strength as soft wire also costs less per kilometre.
The wire component represents approximately 50% of the cost of a fence. Consequently it is important that the correct type of wire is used to achieve stock control at the most economical cost, but at the highest quality. This will ensure that maintenance costs over the lifetime of your fence will be minimal.
Fence droppers perform three functions. They act as a wire spacer, distribute shock loads to the whole fence from individual wires and act as a visual barrier. With droppers, (approximately 1/3 the cost of steel posts) it is obvious that where they can be substituted, considerable savings can be achieved. When using droppers, it is important to ensure that droppers remain clear of the ground so that stock pressure is not taken by the dropper but by the wire component and the strainer assemblies.
With the use of high tensile wire, wide post spacings can be used and it is practical with the use of fence droppers to employ post spacings of 20-30 metres in good conditions. Please note there are many factors that influence post spacing decisions, and you may want to use tighter fence post spacings for added strength in high pressure areas. You may also want to strengthen your fence line by using ‘Intermediate posts’.
Anchoring a steel fence post on a rise or in a dip in hilly terrain can greatly increase the ground holding ability of the fence post and reduces the chance of the post lifting out of the ground with the pressures placed on it from a strained fence line.
Before you start, you’ll need a few extra things. In addition to the post for your fence line, you’ll need:
• An additional post (or at least 60-80cm of a cut off post- ensuring there is a hole near the top of the post) and
• Approx. 1m of fence wire. Use 3.15mm or 4.00mm wire if soft wire is available.
• A sledgehammer is also needed to drive in the anchor post.
1. Drive the post into the ground. For best results, anchor the post at the top of a rise and at the base of a dip.
2. Place the second post (the anchor post) on a 45-degree angle from the vertical and drive it in just behind the main fence post.
3. Continue driving the anchor post with a sledgehammer until it is only a few centimetres from being flush on the ground.
4. Feed the wire through the top hole in the anchor post and through one of the bottom holes on the main fence post. Once fed through, tie the wire so that it cannot come undone. Don’t be concerned if the wire doesn't seem too tight – this will be rectified in the next step.
5. Once the wire is secured and tied off, tap the anchor post the remaining few centimetres into the ground until there is tension on the wire. Your anchor post is now complete.
Fences are an integral part of any property and they are essential for the good management of stock, pastures and crop. On an average property, they represent between 30%-35% of improvements or 5 1/2% to 6% of capital invested. There are four basic components in a fence: strainer assemblies, posts, droppers and wire.
A good fence is an investment. Designing your fence correctly before you start and using the right materials will help to maximise the value of your investment over the life of the fence. However, even the very best fences will require some maintenance to ensure ongoing peak performance. There are factors outside of your control that will require attention over time. Environmental conditions like floods, fallen branches and stock related wear and tear are all issues that can impact a fence's performance.
1. Check regularly
Walk or drive along your fence lines regularly to check for fence line failure points. Most maintenance can be done on the spot using tools and accessories.
2. Clear along fence lines
Remove any debris or fallen tree branches on or around your fence line. The debris that is left behind from storms and floods can become entangled on your fence. Left unattended over time, wet waste can affect the coating of your wire and posts, causing rust or corrosion, or provide a way over the fence for feral animals. Remove or trim grass that grows up around the posts and wire along your fence. It promotes good air circulation to keep the steel surfaces dry, slowing the effects of corrosion. It also reduces the combustible material around the post in the event of a grass fire, reducing the chance of extreme heat damage.
3. Repair erosion points
After heavy rain, check that soil erosion under your fence does not compromise your boundary and let stock out or feral animals in.
4. Check posts and wire tension
Straighten or replace broken posts with the same or stronger posts. Over time, things like stock pressure, fallen tree branches and general wear and tear can also cause your wire tension relax.
Six simple steps to designing your fence.
Whether building a new fence or updating an existing one, ask yourself a few simple questions before you rush out and buy the same materials you always have. Spending time designing your fence may save you time and money when building and maintaining your next fence - the result will most likely be a better performing fence.
1. Map your property.
Sketch out on paper a map of your property or print an aerial image of your property from free online sources such as Google® maps.
2. Mark boundary fences.
Mark out the boundary fence lines, corners, angles and gates on your property map, avoiding natural obstacles like creek beds where possible. If your map is to scale, this will help with calculating the length of your fence lines.
3. Mark internal fences.
Designate certain areas (grazing, laneways, yards or cropping) of your property. This will help you determine the level of pressure your fences will face and what products will help you address that. Generally, high pressures require more posts and wire and low pressures require less posts and wire.
4. Internal and external forces.
Think about what you are trying to keep off your property. A fence can be breached in one of three ways - Over it, Under it, or Through it. If feral animals are a threat, note the characteristics of those animals - do they jump, burrow or charge fences. Your answers will help you choose the right products for your needs. Careful consideration should be given to designing a strong boundary fence using the best quality materials you can afford.
5. Natural forces: fire and flood.
If fire is a common occurrence, consider using low-medium tensile wire which helps minimise the chance of the wire snapping or losing tension under the heat of the fire. If flood is a common occurrence, consider using stronger posts to strengthen the fence line and high tensile wire for the best protection from corrosion.
If your property is rocky and hard, consider using shorter steel posts that you don't need to drive in too far and are easier to install. For loamy and soft soils, consider using longer steel posts that you can drive further into the ground to establish better ground holding. Also consider the slope - for flat ground, post spacings may be increased and most wire products are suitable, but for sloping ground, post spacings may need to be closer to assist with wire attachment.
Fence posts perform two basic functions in a fence. They support and space the wire component and give the fence resistance to overturning. Fence posts are not the barrier to stock, this is the function of the wire component.
The depth the post is put into the ground will affect the strainer’s performance. The deeper the better. By increasing the depth from 75cm to 90cm the total load carried can be doubled while vertical and horizontal movement is reduced.
Therefore strainer posts should be driven into undisturbed soil to a minimum depth of 90cm for best results. There is little relationship between the performance of the strainer post and its size, a 152mm diameter post, provided it is put in correctly, is just as effective as a 609mm diameter post.
The most important component in a fence is the strainer assembly. These are the fence’s foundations, once they fail the whole fence fails. From research work carried out domestically and overseas, it has been found that a driven strainer post can carry much greater loads than a post put into an oversized hole and the soil back filled and rammed. Horizontal and vertical movement is reduced drastically.
A conventional fence is characterised by its “rigidity”:
1. Posts spaced at closer intervals - traditionally 1 to 3 metre spacings trending towards 5 with high tensile wires.
2. A mixture of post types alternating as "Intermediates", e.g. steel, timber and concrete.
3. Typically all line posts are of large dimensions to increase rigidity and visual deterrence.
4. Softer and potentially higher diameter wires, either plain or barbed.
5. Plain wires firmly stapled to posts or wires run through bored holes in wooden posts.
6. More rigid fence wire with either welded, stiff or fixed knot prefabricated wire and/or woven netting.
7. Strainer assemblies generally designed and constructed with lower load capacity.
In conventional fences most of the loads are borne by the line posts nearest the point of impact.
A suspension fence is characterised by its ability to “distribute load”:
1. Wider spaced posts of uniform type (optional use of intermediates).
2. Longer strains and the ability of wire to transfer load with movement made to the strainer and transfers to strainer posts therefore the strainer post becomes the heart of the fence.
3. Suspended droppers.
4. Higher tensile wire.
5. More flexible hinged or ring joint fences.
6. Measured tension on wires.
7. Strainer assemblies designed and constructed to minimise movement and absorb high load capacities.
In appearance, suspension fencing differs from conventional fencing in the considerably wider spacing of the posts. Impact loads imposed on suspension fences are absorbed across a greater length of fence than a conventional fence, where the impact force is absorbed more locally to the point of impact. Some components of a suspension fence will sacrifice to ensure the overall integrity of the fence. The benefits of suspension fencing are lower costs for material and labour and in most instances equivalent stock control as conventional fencing. Maintenance is typically easier and more cost effective with components replaced “in line” and repaired without pulling down the whole section. Examples of this are replacing a post that has taken the impact and yielded through to the replacement of a ring or re-stretching a hinged fence.
Both conventional and suspension fences have a place – knowing what you want from a fence and the conditions it is likely to face whilst weighing up costs and design are key decisions prior to deciding the best option for you.
The addition of a roll of woven or prefabricated fence above the main structure of the fence. This “topper” is designed to increase height and generally deliberately left with less support to force climbing animals back to the ground. This section of the fence is typically not under significant strain to reduce rigidity and to make it harder to climb.
To apply a load to fence wire, usually with wire strainers. Wire has a "breaking strain" and a "recommended tension". The recommended tension is the point before elongation of the steel granular structure will occur (with a safety margin). In prefabricated, netting and barbed wire fences - the design of these products with reverse twists or "tension" crimps will be damaged if wire is "over tensioned" even if only briefly - such as by the shunt of a vehicle sometimes used to "pull-up" a strain.
For this reason the recommended tension is lowered to protect the designed performance of the product. Maintaining correct tension on a fence through maintenance will prolong the fence life.
The normal commercial grade of zinc coating obtained from the hot dip process. eg. Australian Standard (AS 2423:2002) 40g/m2 on 2.50mm wire.
A prefabricated fence having wire pickets permanently but flexibly jointed to the line wires.
A thicker layer of zinc coating, eg. Australian Standard (AS 2423:2002) 230-240g/m2 on 2.50mm wire.
A rotating platform for running out wire from one or more coils or reel.
A more ductile wire able to withstand lower loads than high tensile wire achieved by re-setting the elongation of the steel grains as a part of the production process. In the Australian Standards this is referred to as wires with a breaking strain of 350 to 700 MPa. These wires are often used with higher diameters in areas or sections of a fence prone to grass fires or used where injury to very valuable livestock is a concern - such as horses.
The wire which forms the top and bottom of wire netting. Also fence wire clipped to the top and bottom of wire netting or prefabricated fence to support these products in a fence.
A modern type of weave for netting which aides in the ability of the netting to absorb force.
A fence post which is a vertical member set into the ground.
The vertical wire fixed to horizontal or line wires in prefabricated fencing.
A woven wire hexagonal mesh made from soft wire. Used to contain or exclude small animals, birds and fish.