Treated Woods

• Preservative chemicals applied to wood prevent the growth of fungus and bacteria associated with wood decay. Most commonly, processors treat pines and other softwoods. The process involves using high-pressure applications of chemicals that often impart a light green color to the wood. Pressure-treated wood is sometimes referred to as green treated or pressure treated because of this process. Treated lumber is the most commonly available wood product for outdoor deck and trellis projects.
  
  

Natural Woods

• The heartwood of red cedars, cypress and redwood trees are naturally resistant to rot and decay. Only the heartwood, the center of the tree, possesses these traits. The sapwood, the portion of the tree just under the bark where sap flows, does not have the preservative qualities. Select only the darker colored heartwood rather than the light or tan colored sapwood for outdoor projects. Costs for quality naturally-resistant woods usually exceed treated lumber.
  
  

Composites

• Wood/plastic composites (WPC) utilize a dust or flour made from wood along with plastic resins to create boards. The material is very durable and not subject to decay. It is available in a number of colors and surface textures, such as wood grain. WPC requires no staining, varnishing or maintenance. It does not have the natural appearance of wood and is often more expensive than the wood alternatives.
  
  

Installation and Maintenance

• No matter the material, proper installation and maintenance improves the appearance and durability of the deck or trellis. Install all components with galvanized or stainless steel fasteners such as nails or screws. Apply a water-repellent finish about every two or three years to natural or treated woods. Water repellent finishes aren't required on composite woods.