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Forest Products

Proper Use of Wood Outdoors

Wood as a construction material is subject to decay by fungi and deterioration due to weathering. If outdoor wood is to provide long-term service when exposed to the weather, some strict guidelines should be followed. 

Select the Right Wood for the Intended Use
First, select the right type of wood for the intended use. Only naturally durable or preservative treated wood should be used for outdoor applications. Lumber manufactured from the heartwood of cedar or redwood is one very suitable choice. The other choice is wood treated to the proper level with a leach-resistant, water-borne preservative such as chromated copper arsentate (CCA). 

Use Properly Dried Wood
Second, make sure the wood is properly dried. For outdoor use, wood should ideally have a moisture content between 12 and 15 percent. Construction lumber is commonly available dried to moisture contents of 15 or 19 percent. 

Use Corrosion Resistant Hardware 
Third, use only corrosion-resistant nails, screws, and bolts when fastening lumber or plywood used outdoors. High quality galvanized, aluminum, stainless steel, and other types of special fasteners are available. Only water-proof adhesives should be used; resorcinol resin and special elastomerics are on the market. 

Use Exterior Grade Finishes
Fourth, provide weather protection. Wood can suffer damage when exposed to the action of sunlight and water. A variety of exterior finishes are suitable; for many exposures, water-repellent preservative formulations or oil-base, semi-transparent stains are the most appropriate choices. Exterior paints can also be used; avoid use of clear varnishes outside because of limited durability.