Composite Decking - An Introduction
Until the early 1990’s decks were made of wood. Life was simpler then. The choices were limited. Homeowners thought a lot about the size, location, and design of the deck but didn’t have to ponder too long on what the material would be. Before “decks” became the thing to have, houses had porches. A porch typically had a roof and was built of the same kind of lumber the house was built of …. and then painted. Always painted. And every few years would be painted again.
A deck, having no roof and being exposed to the elements through four seasons of hot and cold, wet and dry, was murder on regular house building lumber. Pressure treated wood had been around for a long time but became the standard for decks. But even pressure treated decking weathered over time.
Then along came composite decking introduced by Trex. Composite decking is a mixture of wood particles, sawdust, or wood chips and bits of ground up plastic. One of the big advantages was recycling and the use of lumber mill byproducts. Lumber mills now had a market for their sawdust and wood chips. Recycled plastic bottles and bags had a good use. The composite manufacturer mixed up a porridge of these materials, heated it until the plastic was melted and ether extruded it through a die with the cross section of the board or formed boards in molds under pressure.
Early composite decking was less than ideal. So companies opted to cap the composite with a thin layer of PVC (vinyl) or Polyethylene. The capping solved a number of problems. It made the decking water proof, which meant it would no longer absorb moisture. It also provided for a spectrum of colors and variety of surface patterns resembling the grain of real wood. Now most composite decking is capped. With some manufacturers, their web sites are not clear on whether their version of composite decking is capped.
Now after a quarter of a century of the growing popularity of decks and composite decking, many more companies have gotten into the game with many innovations and variations of the product. The choice now is more complex than ever. When you look at all the options, you discover a number of decking products that are not composite at all, but instead made completely of vinyl with no wood content. One company makes decking with straw in the composite, rather than wood chips.
Composite and vinyl are far from the whole story on decking. Alternatives to pressure treated wood include various treated and untreated hardwoods, aluminum, bamboo, fiberglass, fiber reinforced cement, and even steel. Each manufacturer will explain why their product is better, so it becomes a fairly complex subject.
Some manufacturers offer a wide selection of colors. Some have variation in the color to more closely resemble real wood. Some composite decking has no variation in color and has a look of painted wood, even when it has a surface texture resembling grain. So if the look of your deck is important to you, you should check a number of sources before making your selection.
Composite Decking is not a structural material. It does not have the strength that wood has. The structure of a modern deck is still made from treated lumber or another structural material such as steel. The structure is the posts, beams, and joists that support the decking.