The Benefits of Treated & Untreated Cedar

CCA Treated Lumber

• Lumber intended for use outdoors is often treated by the manufacturer with chromated copper arsenate (CCA), a chemical that gives the wood increased resistance to decay and insect infestation. Cedar wood benefits from a natural resistance to rot and insects, so cedar lumber is typically not treated with CCA. Untreated cedar is not likely to last as long as treated lumber, but the fact that it does not contain the chemical preservative is enough to make it a more attractive choice for some buyers.

Natural Rot Resistance of Cedar

• Cedar does not require chemical preservative treatment because its heartwood is infused with natural compounds that repel insects and kill the bacteria that cause decay. These compounds, found also in woods such as redwood and cypress, make cedar much more able to withstand exposure to the elements than untreated wood that does not contain them. The natural compounds accumulate in the inner heartwood as the tree ages, so lumber made from sapwood or new growth has less natural decay resistance.

Fire Retardant Treatment

• Cedar does benefit from treatment with a fire retardant material, and wood used to make shakes and shingles for buildings is often given this treatment. Fire retardant treatment may make cedar shingle roofs acceptable under local building codes in areas where fire danger is high. Cedar building materials may also be treated to improve their resistance to the growth of moss and fungus, as well.

Pre-Finished Cedar

• Cedar building materials that will be painted can be pre-finished at the factory during the manufacturing process, either with an undercoat of primer or with primer plus a top coat of acrylic paint. This pre-finishing ensures that the wood is properly coated, the finish properly cured and the surface treated with a coating that prevents damage from ultraviolet sunlight and mildew growth. The finish is a surface treatment only, and care must be taken during construction not to damage the finish.