Fences and Gates

Chain-Link Fences

Chain-link fencing and the associated hardware are frequently used as a physical security barrier. Chain-link fences used for physical security must be constructed with wire that is 9 gauge or heavier. They must be made from galvanized metal fabric with mesh openings no larger than 2 inches and have twisted and barbed selvages at the top and the bottom. The selvage is the way the mesh fabric is finished after being woven. The fence fabric must be taut, reach to within 2 inches of hard ground or pavement, and be fastened securely to rigid metal or reinforced-concrete posts set in concrete. On soft ground, the fence fabric must extend far enough below the surface to compensate for shifting soil or sand.

Rusting of the fence fabric or failure to keep the fabric fastened to the posts will weaken the fence. Vegetation and trees that grow on or near the fence may damage it.

Chain-link fences define boundaries effectively, but they can be breached (climbed over, cut through, raised and shimmied under) in from 4 to 12 seconds. Unless chain-link fences are reinforced with aircraft cable, they are relatively ineffective at stopping vehicles.

Except along sidewalks and roadways where people are likely to be walking, chain-link fencing that is properly installed and maintained can be used as the foundation material for fence protection sensors. These sensors and their associated processors detect attempts to climb, cut, or raise the fence fabric.

A chain-link fence usually is topped with barbed wire, barbed tape, or barbed-tape obstacle. Such toppings make it more difficult (and painful!) for a spontaneous climber to climb the fence, but just delay the prepared, determined climber.

Pedestrian or vehicle gates installed in spans of chain-link fence must be designed so they do not diminish the level of protection offered by the fence itself. Gate latch and lock hardware must be protected by hardened covers that make it difficult for anyone to force them open using handtools. Most commercial gate hardware cannot withstand a hand tool (hammer and cold chisel) attack. Fasteners, such as bolts, must be peened after installation to make them difficult to remove.