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Woods For Outdoor Furniture

By Vincent Lawrence
http://www.plowhearth.com/magazine/woods.asp

 

Plain old pine and ordinary red oak are just no match for the elements. Furniture made of either of these woods, while fine for indoor use, won't last long outside under drenching rains or the harsh rays of the sun. For a piece of outdoor furniture to stand up to the ravages of nature - even in a relatively mild, balmy climate - it must be made of a wood with some natural resistance to rot and insect infestation.

Woods work in two very different ways to resist rot. Some, such as redwood, cypress, and the cedars (there are many cedars), contain chemical compounds that bugs, bacteria, and other agents of decomposition find offensive, so they look for their meals elsewhere. Other woods, such as white oak and black locust, have physical barriers to rot, structures called tyloses that fill the pores of the wood, preventing moisture, and the decay-causing creatures that thrive in moisture, from getting into the wood in the first place. Either way, chemically or physically, the result is the same - these woods stand up to the elements, season after season.

So, what other woods are sufficiently rot-resistant to be used for outdoor furniture? Well, there are lots, but they fall into just two main categories: the sleepers - domestic species that are more commonly associated with fine, indoor furniture - and tropical species. The first category is fairly small. In addition to the already mentioned white oak, both black cherry and black walnut are fairly rot resistant, actually on a par with some of the cedars. Because of the expense of these woods, though, they're rarely used for outdoor furniture.

Of the hundreds of tropical species, there are dozens that are well suited for outdoor furniture, but the two most notable and familiar of these are teak and mahogany. Both of these woods have been so overharvested, however, resulting in deforestation in South America and Southeast Asia, that many outdoor furniture manufacturers are now using lesser-known species with similar characteristics. (Also, some manufacturers have switched to plantation-grown teak.) Some of the lesser-known species showing up as furniture, decking, and the like, these days are balau, eucalyptus, ipe, iroko, jarra and kempas. Though not as familiar as the species they largely replace, these woods are also stable (therefore warp resistant) and rot resistant, fairly hard and fine grained. Chances are you'll be seeing more of them in the years ahead.

Care for any of these woods - from the cedars to kempas, and every one in between - is exactly the same so long as the wood is either unfinished or treated with an oil finish. For unfinished woods, which generally turn a beautiful silver or gray as the years go by, a light sanding with 150- or 180-grit sandpaper once a year will knock down any fuzzy grain (caused by rain and/or snow), eliminate any larger fibers that could cause splinters, and generally give the wood a clean, smooth look. Don't be overzealous in sanding, however: You don't want to sand through the silver and expose the original color of the wood once the furniture is on its way to developing a natural patina. Furniture with an oil finish should be sanded in the same manner - once a year - then given a light coat of whatever oil the manufacturer or retailer recommends. That's all there is to it.