What are Pressure Treated Split Rail Fences?

Pressure treated split rail fences are fences that usually form a zigzag pattern. They are made of logs which are split lengthwise and held together with spikes to form the rails. Split rail fences need a lot of timber and are thus not common in areas where wood can be scarce.

The wood used for the fence, such as cedar, is split from one end to another to make rails. These rails are stacked one on top of each other, sometimes in an interlocking "zigzag" pattern, which makes it more durable. This also facilitates disassembly, repair and assembly. The rails are sometimes stacked directly on top of one another with the use of double fence posts. This system makes for a more compact structure that could easily be disassembled for repairs.

Pressure-treated wood

Pressure-treated wood is used for creating split rail fences. In order to enhance the split rail fence's strength and durability, the wood used as its main construction material is treated with preservatives to prevent wood rot, fungal growth and insect infestation.

This treatment helps the wood last longer even under harsh weather conditions. The most commonly used preservatives for pressure treatment include pentachlorophenol and chromated copper arsenate (CCA).

What is the process involved in the pressure treatment of wood?

First, a container is filled with the preservative solution and the wood is placed inside it. As the pressure inside the container builds, the preservative is forced into the minute spaces in the wood to protect it against wood rot and insect attack. Second, the excess preservative is drained and eventually recycled.

The chemicals used to treat wood for residential and general construction are copper azole; ACQ or copper quat, which is a copper oxide-quaternary ammonium mixture; DOT or disodium octaborate tetrahydrate; and others.

Which types of wood can be pressure treated?

Logs that are used as construction materials have various layers, and foremost among these layers are the heartwood and the sapwood. While the hardwood lends the tree its structural strength, the sapwood is the part which carries the sap from the tree's base to its branches and leaves.

In pressure treatment, sapwood is known to absorb the preservatives better than heartwood. The types of lumber that are preferred for this process are those that have a higher percentage of sapwood, such as Southern Pine.

Those that have more heartwood, such as Douglas Fir, need to be slightly changed for them to absorb and retain sufficient preservatives. A method which can be employed to improve their absorption and retention is perforation of the wood with small slits to increase the preservatives' penetration.

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