About Composite Decking Material

Composite, or engineered, wood is a building material made of wood or other cellulosic materials mixed with a binding agent to create a material that is stronger, denser and heavier than wood alone. Composite materials can be fabricated as veneers, plywood or as structural materials. New types of engineered lumber have given homeowners a growing choice of attractive options for exterior construction, such as porches and decks.

History

Plywood--the first composite material--is less durable than solid wood for decks

Wood was the material of choice as outdoor decking became more popular in the 1970's. Beginning in the 1980's, new plastics and adhesives were combined with straw and other waste materials, such as wood chips and shavings, to fabricate deck materials. These new products offered the look and workability of wood, but they were more water resistant and required less maintenance. Replacements for formaldehyde-based adhesives and improved designs have increased the acceptance of composite decking. Although the majority of decks are still built of pressure-treated pine, redwood, cedar or mahogany, use of composite woods has increased as outdoor decks and living areas have become essential home features over the past decade.

Features

Composite materials bind fibers with adhesives and resins

Standard wood-working tools and saws can be used with composite deck materials. They can be joined using nails and screws without pre-drilling or other preparation. Composite deck boards will not delaminate and does not need to be sealed. Some is fabricated with hollow cores to minimize weight and make it easier to handle.

Benefits

Fabrication can limit weight

Composite materials come pre-finished; painting or staining is not necessary. Composite materials cost about the same as treated lumber, but their longer life and low maintenance requirements may make them more economical in the long run. Materials are available in a wide range of pre-formed pieces that can be easily assembled to form railings, stairs and other assemblies common to decks. Since many composite materials utilize fibers, plastics and other materials that would normally be discarded as waste, they are considered an efficient use of resources.

Types

The most popular types of composite material used for exterior decks are wood-plastic composite (WPC), polypropylene or vinyl extrusion products.

Considerations

Any engineered material that vents formaldehyde should be avoided. Alternative resins are being developed to replace the Urea-, Phenol- and Melamine-formaldehyde adhesives (UF, PF and MF) originally used in composites. Polyurethane (MDI) resins do not release formaldehyde and are considered resistant to humidity and water.

Resources

• Wood-based Composites and Panel Products
• North American Deck and Railing Association--links for homeowners and professionals
• Composite decking materials reviews