Composite Decks Ardmore OK
Decks are an important part of our homes and lifestyles. As transition areas between the inside of the house and the yard, they can provide space to entertain or just a pleasant spot to drink a cool one on a summer evening.
Estimates put the number of residential decks in the United States at more than 30 million. And about 3.2 million new wood decks, porches, verandas and balconies are built every year" either as part of a new home, an addition to an existing home, or a replacement for older installation. Estimates of the total cost for all those new decks range from $1.9 billion to $3 billion.
Deck components can be divided into structural (posts, joists and stringers) and non-structural (decking and railing) parts. Structural components are almost always made from pressure-treated wood, but there is more variety in decking and railing.
In fact, the most popular decking and railing materials are pressure-treated wood, at about 80 percent of the market, followed by woodfiber-plastic composites (WPCs), at 8 percent, redwood (6 percent), cedar (3 percent), plastics (2 percent) and other materials (1 percent).
The rapid growth in composite decking is one of the most exciting stories in recent residential construction. It went from a market share of 2 percent in 1997 to about 8 percent in 2000 and is projected to have a 20 percent market share in the United States by 2005.
It's a little hard to define just what WPC decking is because of the huge range of products that fall into this category.
It is generally agreed that a WPC is a mixture of a thermoplastic, such as polyethylene (commonly used to make plastic toys and milk containers, plus a lot of other products), with wood flour or fiber, with at least 40 percent of the composite being wood.
From there, though, the decking products vary widely. Differences can be subtle, such as the type of plastic used (polyethylene, PVC or polypropylene), wood species (pine, maple, etc.), or wood-particle size (flour, fiber or sawdust). Differences can also be very striking, such as the color and cross-section profile. Colors vary from light tan to a dark brown. When viewed on the cut end, the decking can look like a solid piece of wood or have a complex, engineered profile.
A lot of the variation in WPC decking comes from the large number of manufacturers, each of which has a different concept of the perfect deck board.
All the current products have something in common, though: They are formed by extrusion. A hot mixture of plastic and wood particles plus a variety of additives are squeezed through a die, like toothpaste out of a tube, then through a cooling section to harden the plastic. The continuous extruded product is cut to appropriate lengths, usually 16 feet. The shape of the die determines the cross-sectional shape of the deck board.
Although we are dealing with decking products in this article, WPCs are used in a number of other applications" deck railing components, window and door parts, automotive interior panels, marine docks, industrial flooring and agricultural fencing.
Other non-decking, exterior applications are under development" siding, trim, fascia boards, fence components, even roofing. This large product range is possible because of the extrusion manufacturing process, which lends itself to a wide variety of cross-section shapes and sizes.
Most homeowners want building products that look good and perform well at low cost. Most WPC decking products look very good, at least when they are new. Judging from the growing WPC market share, it seems many do-it-yourselfers and homebuyers agree.
But be aware of one thing: Color changes after installation. I have seen a product that is an attractive brown, when new, turn a rather unattractive blue-gray after exposure to sunlight. In general, the lighter the color when new, the less of a color change you can expect later on. Light-colored decking is better for another reason" it will reflect more sunlight and won't get as hot during the summer. This makes it more comfortable to walk on with bare feet.
Another important aspect of the overall positive look and feel of WPC decking is the straightness of the boards and their consistent appearance. There are no knotholes or areas of raised grain, as you can find with treated solid wood. You also cannot get splinters from WPC decking" a major advantage if you have small children running around on your deck with bare feet. Some decking products also have a roughened surface that provides good traction, even in the rain.
WPC decking is also more dimensionally stable than solid-wood products. A common problem with conventional treated-wood decking is shrinkage after installation. It can be very frustrating to have the initial small, even spaces between your boards open up to yawning crevasses after the wood boards dry and shrink.
Installed gaps between composite deck boards stay the same after use. Manufacturers also claim WPC decking does not warp, cup, twist or cause loosening of fasteners. Similarly, these products do not require much maintenance compared to solid-wood decking. Staining, waterproofing or sealing the surface is not necessary.
There are also environmental advantages. The wood component is typically sawdust and/or planer shavings from lumber mills, or ground-up shipping pallets and other wood packaging materials. These composites allow efficient use of forest resources.
Many manufacturers use plastics that are recycled. In fact, plastic-based building products were originally developed to be a major consumer of recycled plastics. The volume of WPC products has, however, outgrown the supply of recycled plastics, so the industry now consumes a lot of virgin plastic as well.
Another related environmental issue deals with wood preservatives. WPC decking typically does not contain any wood preservatives. It is considered to be inherently resistant to decay fungi and insects. All the issues surrounding arsenic and other heavy metals in pressure-treated wood are avoided. (See our related story on CCA-treated lumber in the Home Front section.)
All these characteristics lead to a low-maintenance, environmentally friendly deck, but there is a cost.
WPC decking is more expensive than conventional pressure-treated pine. It depends on the market area, but expect to pay 60 to 70 percent more. This makes composite decking roughly the same price as redwood or cedar lumber. It can also be difficult to get a particular WPC product because of limited distribution. You may see an advertisement for a particular type of WPC decking in a magazine, but it may not be readily available in your area.
With the large variety of different designs and compositions of WPC decking, it can be hard to make generalizations. The types that have a solid cross-section (rather than open channels) are usually quite dense, making the boards about twice as heavy as conventional treated solid wood. This makes the decking more difficult to handle and translates into increased labor costs.
That problem is overcome with the non-solid designs. The high density can also be a problem for fasteners; pre-drilling is often necessary. Even countersinking screw heads may be required, although some new designs avoid that need. Again, this adds to labor cost.
One property that is consistent, however, is that all WPC decking products are substantially weaker than solid wood. For decking, stiffness is particularly important. With solid-wood decking, you can often use 24-inch centers for the joists.
This is not recommended for most composite plastic deck boards. Because of the low stiffness of the composite, the deck surface would feel quite springy and not very solid. You also run the risk of the boards sagging over time. You should use 16-inch centers for composite decking, which also can increase the total cost for the deck, because more joists may be required. Of course, the same spacing considerations apply to stringers when composite boards are used for steps.
In some warm, moist climates, some WPC products are also initially prone to mold growth. This typically happens immediately after installation. The mold will grow until the nutrients on the composite surface are used up, then the boards will be mold-free afterward. If this happens, the deck surface can be cleaned with a diluted bleach solution, or plain soap and water. This temporary problem usually doesnt affect long-term performance.
Some of the WPC deck boards have a glossy or semi-glossy surface that can look very good, but remember that the surface is soft and prone to scratching and wear. Moving barbecues, plant pots or patio furniture can easily scratch the surface. Scuffs from just walking on the surface can lead to wear patterns. The surface of the boards near doors or down the center of steps can soon look much duller than surrounding areas. For some people this can be a real problem.
The decking products with an open-channel structure to them have some advantages" they are less dense per foot of board, and they may be cheaper than the solid boards. One thing you have to be very careful about with these designs is the placement of fasteners. Over-driving a screw at the center of a channel can crack the board or at least cause a large indentation in the board surface.
The Bottom Line
There is no doubt that there are a lot of advantages to using woodfiber-plastic deck boards. The lack of splinters and the use of no wood preservatives are especially important for many people.
The major confusing factor is the large variety of products on the market. How do you choose which one to use on your deck? I would be especially concerned about what the decking is going to look like in a year or two. The boards will weather differently in different environments.
The safest approach is to look at what products are available locally, choose a couple based on your taste, then ask the retailer if they can point you to local installations of those products. Then you can get an idea of the color changes, potential for mold growth in your climate, and surface wear that can occur.
Color changes should also be taken into account during deck design. Initially, a composite deck board may have the same color as solid wood. But are they going to weather to the same color? If you have large areas of wood exposed in your design, as well as the composite decking or railing, you may notice the wood and composite areas look very different after weathering and don't coordinate as well. Also, remember that composite deck board designs with an open cross-section look best if the ends are covered with a trim board.
You should read the installation instructions before you buy. If you are not prepared to pre-drill holes, don't buy a product for which this is required. Don't expect these products to behave the same as treated wood.
Because these are relatively new products on the market, there is not a long history of use. The manufacturer's brochure will typically show beautiful, freshly built decks. You want to know what your deck will look like after a few years? Read the brochure and warranty carefully, and if possible, look at the product after it has been in service for a few years in your area.