How to install a fixed knot fence, step by step

Before you start

High tensile wire behaves differently from ordinary chain link (jali): it is stronger, springier and stores more energy under tension. Read the whole guide before you start, and download the installation manual for the site.

• Safety. Wear gloves, eye protection and safety boots throughout. Never stand in line with a wire under tension or in front of a fence puller. Secure every cut end: a released high tensile wire can whip. Keep children and animals away from the work area.
• Why it matters. A knotted fence is a system: its rated life depends on correct posts, bracing, joining and tension as much as on the wire. With correct installation, SIMO Securon is rated for 35 years or more (Alpha), 20 years (Zeta Nova) and 10 years (Pi), in C1 to C3 environments.

What do you need to install a fixed knot fence?

• Fence puller

• Tensioner

• Wire twister

• V-Clip

• C-Clip

• Fabric lock

• M10 fastener

• Angle post

QvikFixrr™ installation tools: a fence puller draws the fabric along the line before it is fixed; a tensioner, fitted at the terminals, brings the line wires to tension; a wire twister ties off the wires and makes the splice-and-twist joins; wire grip joiners grip the line wires. Fence supply orders of 2 km running length and above come with one set of the three tools free, for the project.

General tools: measuring tape, string line and marking pegs; a post-hole digger or auger; a spirit level; concrete mixing tools; wire cutters rated for high tensile wire; spanners for M10 fasteners.

Materials:

• SIMO Securon fence fabric, in the grade and grid specified
• QvikFixrr angle posts with standard 8.5 ft shafts: 50 x 50 x 6 mm for regular spans and 65 x 65 x 6 mm at terminals and corners; or concrete columns of at least 150 x 150 mm in high-grade concrete
• Bracing struts and horizontal stays
• QvikFixrr V-Clips and C-Clips (staples or clips for the stays), fabric locks and M10 fasteners
• Wire grip joiners for the line wires, and wire tensioners for the terminals
• Concrete, and gravel or crushed stone where the ground needs drainage
• Toppings where specified: RTHT™ high tensile barbed wire and concertina coil

How do you plan the line and work out quantities?

Walk the whole line first. Mark every terminal, corner, change of direction and gate before anything is dug. Every gate is two terminals, and every change of direction is a corner, braced both ways.

• Perimeter: measure it. A square plot of 1 acre is about 255 m around; 5 acres is about 569 m.
• Intermediate posts: each straight run divided by the post gap. At 5 m, 569 m needs about 114 posts; conventional galvanised chain link at 2.5 m would need about 228.
• Terminals and corners: count them from your plan; each gate adds two.
• Fabric: each straight run divided by the roll length, rounded up: Alpha 50 m, Zeta Nova 30 m, Pi 100 ft (30.5 m), ZS-Knot 50 m.

The fencing cost estimator works out the boundary, posts and rolls for you.

Check the site first. Within 20 km of the coast, or on a chemically aggressive site (C4 and above), for example near chemical plants, fertiliser stores or industrial fumes? Stop and ask SIMO for a site-specific recommendation before ordering.

Step 1: set out the line

• Run a string line between terminal positions, pulled tight at the height of the fence base.
• Mark each post position along the line: every 5 to 6 m for Alpha, every 5 m for Zeta Nova and Pi.
• Check the line is clear of buried services before digging.

Step 2: how deep should fence post foundations be?

A post is the fence height plus at least 50 cm, set into the concrete: the standard 8.5 ft shaft on a 6 ft fence gives about 76 cm. Use angle posts of 50 x 50 x 6 mm (65 x 65 x 6 mm at terminals and corners), or concrete columns of at least 150 x 150 mm. Place gravel or crushed stone at the base of a posthole where the ground needs drainage.

Step 3: how do you brace terminal and corner posts?

1. Diagonal brace at 45 degrees on every terminal post
2. Horizontal stay between the terminal and first supporting post
3. Terminal foundations at least 45 x 45 cm and 75 cm deep; corners 60 x 60 cm, braced both ways
4. Fabric tensioned only after the concrete has fully cured
5. Posts set at least 50 cm into concrete; concrete posts at least 150 x 150 mm

Every terminal post is braced, because it carries the pull of every line wire. Corners are braced in both directions, one assembly for each line leaving the corner, on a foundation of 60 x 60 cm, 75 cm deep.

How do you fit a gate in a fixed knot fence?

Treat each gate post as a terminal: braced the same way, on a terminal foundation, so the weight of the gate never hangs on the fabric. Hang the gate only after the concrete has cured, and fit the top hinge with its pin pointing down, so the gate cannot be lifted off. Leave enough clearance for the gate to swing over the highest point of the ground, and check that it opens, closes and latches freely before handover. Gate size and fittings are specified for each site.

Step 4: set the line posts and let the concrete cure

• Set each intermediate post plumb on the string line, checked with a spirit level in two directions.
• Keep post heights even, so the fabric sits at a constant height.
• Use rust-free posts only: a rusted post shortens the life of the whole fence.

Do not rush this. Let the concrete cure fully before any tension goes on: tensioning early pulls terminals out of line and loosens the whole fence. Keep the concrete damp, and wait at least 7 days with ordinary Portland cement (OPC), or at least 10 days with PPC or another blended cement, or in hot, dry weather: the curing periods of IS 456. If in doubt, wait longer.

Step 5: run out, anchor and join the fabric

• Unroll the fabric along the line, next to the posts, and stand it upright.
• Check which way up it goes: on a graduated grid, the closest wires go at the bottom, where animals push and small animals try to get through.
• Anchor the start at the first terminal with a flat bar fabric lock and M10 fasteners.
• Join rolls on long runs by splicing and twisting the line wires together: no welding and no joint, and the twist leaves the coating intact. Never weld or joint the fabric.

Step 6: how tight should a fixed knot fence be?

• Fit the fence puller to the free end and draw the fabric along evenly, so every line wire takes load together.
• Bring the line wires to tension with wire tensioners at the terminal posts, using tension wire grips on the line wires.
• Target: 0.8 kN of installed tension in each line wire (about 80 kgf). Check it with a wire tension meter on every line wire, near the middle of each tensioned run, and bring all the line wires to the same reading.
• Watch the crimps between the stays: they act as springs and should stay visible, not be pulled flat.
• Re-check the terminal bracing: it should not move as tension comes on.

Never stand in line with the wire or the puller while tensioning. Tension slowly and evenly, and wear eye protection.

Step 7: fix, tie off and add toppings

• Fix the fabric to every intermediate post with QvikFixrr V-Clips or C-Clips; staples or clips for the stays.
• Tie off the wires at the terminal with the wire twister; trim and turn in the ends.
• Mount toppings on the post attachments: RTHT barbed wire strands, with concertina coil seated between them where specified.
• On a ZS-Knot 4 x 2 anti-climb fence, keep the toppings continuous across every post, so there is no gap to climb through.

Step 8: inspect and hand over

• Terminal and corner assemblies braced and not moving
• Posts plumb, even in height and free of rust
• Fabric the right way up, fixed at every post
• Roll joins spliced and twisted; no welded or jointed fabric; cut ends turned in
• Tension even along the run, with the crimps still visible
• Toppings continuous where specified
• Site cleared of wire offcuts and packaging
• Care guidance handed to the owner of the fence

How do you look after a fixed knot fence?

• Store rolls closed, dry and off the ground until they go up.
• Walk the line after storms or impacts.
• Keep fertilisers and chemicals off the fence.
• Replace any rusted post early.
• Never weld or joint the fabric, even for repairs. Join rolls only by splicing and twisting.

Download the installation manual

The 12-page installation manual has every step above with its drawings, and the care card fits on one sheet for the site.

Installation manualPosts, foundations, bracing, tensioning and care, in 12 pages.PDF, 588 KB Care and quick-install cardHow to store, install and look after your fence, on one card.PDF, 126 KB

Need a trainer on site? On a supply-only order, an on-site trainer can work alongside your team on tensioning, bracing and fixing, backed by instructional videos: see installation training. Or have SIMO Securon’s own crews install it: see fencing contractor.