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Forest Products Extension

Installing and maintaining wood deck and fence boards

Wood is a good choice for building decks or fences. Either preservative-treated wood (usually pine) or naturally durable woods such as cedar or redwood can provide years of performance, because they resist attack by insects and wood-rotting fungi. However, research shows that many decks are removed after only a few years; not because they are rotten but because they look bad. There are a couple of simple things that can help to preserve the good looks of wood exposed outdoors, and thus increase the longevity of a deck or fence.

Wood outside is exposed to periodic wetting and drying. This can result in surface checks that look bad to many people. A simple way to reduce the risk and severity of surface checking is to install the boards with the bark side down (see the picture). The natural tendency of wood to shrink and swell is uneven, and in “flat-sawn” lumber this makes boards cup towards the side that was closest to the bark side of the log. Orienting deck or fencing boards with the growth rings curving upward means that the board will try to cup towards the back. The result is less checking.

The use of the recommended nails or screws also can help maintain the good appearance of wood decks or fences. Hot-dip galvanized, stainless steel and other coated fasteners are available. This is especially important with the new wood preservative formulations, which can be very corrosive to some metals. The correct fastener will last for years and won't stain the wood.

Good maintenance also can do a lot to prevent checking and to maintain the good looks of outdoor wood. Regular application of a water repellent finish will help the deck or fence to shed rain, and this helps reduce the wetting and drying cycles that cause checking. Preservative treated wood often contains a built-in water repellent, but manufacturers still recommend applying a fresh water repellent finish every year or two.

Wood remains a popular and appropriate choice for building decks and fences. A little care when installing the boards, combined with regular maintenance, will help keep the wood looking good for years.

References

Dawson-Andoh, B., Matuana, L. and J. Harrison. 2004. Mold susceptibility of rigid PVC/wood-flour composites. J. Vinyl & Additive Technology 10(4):179-186

McQueen, J. and J. Stevens. 1998. Disposal of CCA-treated wood. Forest Prod. J. 48(11/12):86-90

Morris, P.I. and P. Cooper. 1998. Recycled plastic/wood composite lumber attacked by fungi. Forest Prod. J. 48(1):86-88

Urban, K. and P.D. Evans. 2005. Preliminary observations on the effect of growth ring orientation on the surface checking of flat sawn Southern pine decking. Proceedings of the International Research Group on Wood Protection 36 th Annual Meeting. IRG/WP 05-20313.

Pressure-treated southern pine decking

Adam M. Taylor
Tennessee Forest Products Center
2506 Jacob Drive
Knoxville, Tennessee 37996

Phone: 865-946-1125
Fax: 865-946-1109

Adam Taylor's email