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Wood Composite Fencing
Recycled Materials Combine to Make a Top-quality Product


Man-made composites, two or more materials combined to create a new, stronger one, have been around for centuries, with bricks being one of the earliest examples. A modern composite material made of recycled wood and plastics by Trex Company is now being used in fencing. And as an example of its strength, it has wind certification of 110 mph and can withstand gusts up to 130 mph.


Wood composite fences mounted on concrete walls are often used for noise abatement. Steel inserts can be mounted right into the concrete, and then the posts and pickets mounted flush to the wall so there is no gap between it and the fence. Not only can the noise not go underneath the fence, it can't go between the interlocking pickets.

A composite material consists of two or more substances that work together, without fully blending or dissolving into one another, to give the new substance distinctive properties. At least one of the substances provides strength, and is known as the reinforcement, and at least one binds the reinforcement together, and is called the matrix. Concrete and fiberglass are two well-known examples of composites.

According to the Royal Society of Chemistry, "The biggest advantage of modern composite materials is that they are light as well as strong." And different combinations of reinforcement and matrix materials allows for composites that can be targeted for specific applications, especially because many can be formed into a wide variety and complexity of shapes.

Wood composites have been around for a while, with plywood being one example, but a more advanced one was developed over 20 years ago for the decking industry by Trex Company. Their material is made of over 50 percent recycled wood, which is combined with recycled plastic bags. The manufacturer refers to it as a wood-alternative composite and now makes fencing products from it.

According to Trex's website, their "special formula takes the strength of wood and pairs it with the durability of plastic," creating a product that is more sturdy than other manufactured fencing products with posts that are 4 times thicker, and therefore don't need to be sleeved over metal or wood fence posts for added strength - though they can be. The fence pickets are solid, not hollow as some competitors' are, yet "only weigh slightly more..., making them just as easy to install, but their resilience means you'll only ever have to install it once."


For fences above eight feet, often it will be required to use 3.5" x 3.5" galvanized steel inserts welded to mounting plates, which are both readily available at local supply stores according to Derek Premac, the vice president of national sales for SRF Fence & Supply Co.



One way to deal with slopes is to rack the fence by shimming the mounting brackets. According to Premac, this is a preferred method of installation. In this case, the bracket on the bottom of the fence (inset) is shimmed by the installer at the angle needed on a section-by-section basis, using wood composite materials at hand.

These fencing products are designed to have a natural appearance similar to wood as opposed to a glossy coating, and are actually over-pigmented in the manufacturing process to allow for some weathering, so when that happens, "the color still looks good," states the website.

Derek Premac, vice president - national sales for SRF Fence & Supply Co., which distributes the wood composite fencing products, relates other advantages such as wind certification of 110 mph and low to no maintenance. And as evidenced by a 25-year warranty, the wood composite material, "still looks the same, while wood products deteriorate."

"Imagine installing a fence that never needs repairs or replacing, a fence that never breaks and always looks good," a representative of the manufacture adds.

Wood composite fencing should have special appeal for contractors and customers that strive to position themselves as environmentally friendly entities. First of all, as already mentioned, the wood element in the composite is all recycled.

"It comes from the furniture mills so they are not felling trees," states Premac.

Together with the recycled plastic in it, 95% of the product comes from recycled materials. It contains no hazardous chemicals and the manufacturing process involves reduced CO2 emissions.



To accommodate grade change, a lot of fences use the stair step method but this creates gaps, which reduces the security qualities of the fence. Wood composites, like wood, allow for a transition cut, as pictured here, by simply cutting the posts and pickets at an angle.

The product even qualifies for LEED points through the U.S. Green Building Council.

Another of its touted advantages is its performance in the the most extreme weather conditions.

"When you build an outdoor fence, you expect it to handle the outdoor weather," the representative says. "This material does not warp and the special interlocking design of the pickets will ensure that your fence is always private. It has even been tested to withstand hurricane force winds facing gusts up to 130 mph."

"You also have the aluminum bottom channel between the two posts, which is rather unique," adds Premac. "Other fence types will sleeve the bottom rail with the material, be it wood or steel." But in this case, a 3/4 " thick piece of aluminum actually is the bottom rail - it is not being sleeved.



A second method to mount a wood composite post into concrete is to: (Top, Left) Weld a Z-channel to a 3/8" plate. (Above) Drill four holes into the concrete, fill with epoxy and attach the channel and plate with 1/2 " concrete anchors. A Z-channel works well for this because it allows better access for fixing the bracket into the concrete. (Top, Right) Sleeve the post over the mount, plumb it and secure it with self-tapping screws.

A common application for the fencing product is to mount it to concrete pads or walls for such things as hiding mechanicals and minimizing noise. Also, the product works well on slopes as the posts and pickets can be cut at an angle, or transition cut, like wood. The system also allows for racking: adjusting the angles of the sections, as opposed to having to "stair step" the sections, which leaves gaps between the ground and the bottom of the fence, making it less secure.

The wood composite system also facilitates installations in areas with bedrock bases.

"They (drill) down to 60 inches or so," Premac reveals, "run a 12-foot post and then sleeve it with an 8-foot or 9-foot galvanized steel insert that will have a further depth and set that in the concrete right inside the rock."

A popular customer for wood composite fencing is homeowners associations, with Premac calling it a one-time, upfront investment.

"There is basically zero maintenance, so the HOA reserves can be diverted to painting, landscaping, snow removal and such," he says. "The break even on the payback versus wood is typically 12-14 years."

And the product's noise abatement qualities make it a cost effective option for commercial and industrial applications.

"Other solutions are usually considerably more expensive, thus at times unavailable," Premac explains.

As seen in LC/DBM magazine, January 2018.

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October 17, 2019, 6:33 am PDT

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