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Wooden outdoor structures can be made more durable: Words to Grow By

If you're planning on building a wooden fence or outside structure, be sure to consider the deteriorating forces that high temperatures and moisture have on wood in Louisiana.

Especially in our warm and humid state, it is important to choose an appropriate wood when building a fence or outside structure. After selecting the wood, a maintenance program consisting of staining or periodic retreatment will give the most satisfactory results.

The principal causes for wood failure in Louisiana are termites and decay rot caused by the state's moist, warm climate. When conditions are favorable for their growth, microscopic filaments of decay fungi grow through wood, breaking it down and using it for food. Fungi and termites both need warmth, moisture and oxygen to grow. Keeping as much wood off the ground as possible will reduce retained wood moisture.

Termites and decay around a structure are a problem where excessive water is either absorbed or trapped in cracks and joints. Because they are in the ground, posts must be pre-treated to resist insects and diseases.

Water that enters the surface checks of horizontal rails and boards keeps internal wood wet enough to decay unless the wood is treated to resist such deteriorating forces. Retained water is even more destructive in shady locations.

Water is absorbed through the ends of wood faster than through the sides. The problem is more accelerated at the ends of rails, braces and boards. A water-repellent preservative can help reduce the problem.

Woods most commonly used for decks and fences in Louisiana are western cedar, redwood, cypress and pressure-treated southern pine.

Chemical treatments and water repellents increase the useful longevity of wood used outdoors. Chemical treatment can be done by dipping, brushing or by pressure. Pressure treatments that force preservative chemicals into weed are better because they provide in-depth protection against both decay and termites for a long time. Generally, Southern pine is the only type of pressure-treated wood available from local retail outlets.

Posts should be pressure-treated unless they are decay-resistant heartwood. Above ground parts of decay-resistant wood may last satisfactorily from 10 to 15 years.

Pressure-treated pine will last much longer. Quality of treatment is not always indicated by the color of the wood. That's because wood fades to a more neutral color after exposure to sun and rain. Penetrating water-repellent stains also may be applied to fence posts to alter the initial color and to reduce warping, checking and cracking.

When buying preservative-treated wood products, pay close attention to the stamps, labels or certifications on them. Treated materials used for posts should be stamped, labeled or otherwise certified for use in the ground, an assurance of maximum durability.

Treated wood marked for above ground use should not come in contact with the ground. However, these materials may be used as above ground components of outdoor structures. A water repellent applied every two years will add to a wood's useful lifespan.

Water repellents are commercially available for use as is or they can be mixed. They help reduce warping, cracking and checking. For wood that is not pressure treated, use a preservative that has a water repellent added. The preservative also helps prevent mildew and mold.

For information contact Alan Vaughn, County Agent, Plaquemines/St. Bernard Parish at 433-3664 or 278-4234.