Q. Am trying to decide whether to use pressure-treated decking or composite as a replacement for my deck, which is 11 years old. Being in the "Elderly Class," we do not use the deck with any great frequency. The pressure-treated compared with composite is expensive. I understand Rust-Oleum has a product that you use as a preservative/semi-transparent stain, which is applied a year after the deck is installed, with a life span of 10 years. I also understand that pressure-treated wood varies in quality. How would I know which is the best?
A. In my opinion, there is nothing better than a quality treated wood or natural wood product when building a deck. If you're looking at a less-expensive composite material, you should be aware that many of the composites on the market today simply do not withstand the elements as well as a wood deck. What I have found is that composites fade and have to be maintained using harsh chemicals and lots of scrubbing. A wood deck, on the other hand, can be treated using stains or sealants, which are applied with a roller, brush or sprayer and a lot less labor.
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Another issue I have found is that composite materials do not have the structural stability of wood. Typical floor joists for a wood deck are set 16 inches on center and, depending on the length of the joists, will hold a 40-pound live load (the same loads the floors in your home are designed to hold).
A composite joist set 12 inches on center might bow under its own weight before you even apply the decking. With composites that contain wood fibers, mold has become an issue that most manufacturers disclaim in their warranty. You may see moss on some wood decks that have been stained or sealed, but I have never heard of mold being a problem with a wood deck.
With wood there is very little expansion and contraction of the materials, but some composites can expand or contract by as much as 2 to 3 inches. This is important to know when designing and installing joists, decking and fasteners.
What kind of wood should you use? Most pressure-treated lumber is either pine or fir. Because the pine and fir are not "old-growth" lumber, the grains in the wood are widely separated and the lumber tends to twist or bend when exposed to the weather. Sealing the wood at the time of installation will reduce the twisting, splitting and cupping of the decking.
Redwood and cedar are two types of wood that can be exposed to the weather without being treated and tend to remain stable in all seasons. I would recommend using pressure-treated lumber for your deck, and as the seasons go by you can replace any of the decking boards that succumb to the weather. Treat the wood as recommended using any stain or sealer of your choice.
• Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at d.Barnett@insightbb.com.
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