Saturday, August 29, 2009

What Woods Are Good for Building Outdoor Furniture?

In my last blog entry I talked about finishing outdoor furniture, then I realized that I hadn’t talked about what materials work well for these pieces. With that said, let’s jump in and cover that today.

Most woods do not work well out doors; they are prone to water damage, mold and fungus infection, and sun or UV degradation. These frequently lead to splitting and splintering which just lets the water, sun and microbes work its magic further into the wood. Paints and oil finishes delay this brake down but the upkeep of the finish on the wrong wood just delay’s the inevitable.

So if most woods don’t survive outside, which ones do, and why? The most readily available are the teak, cypress, mahogany and white oak families. Just to let you know, cypress includes redwood and cedar two popular exterior woods. Let’s look at these woods and what makes them special.

Teak contains natural oils that make it great for exterior uses. Not only do the oils protect the wood from water, but insects and pests too. Cypress, like teak, has natural oils that make it resistant to weather. Mahogany is also resistant to splintering and shrinkage, which makes it a good choice. White oak is rot resistant due to its particular cell structure. This structure, called tyloses, does not allow water to pass through the cell thus preventing the breakdown.

You may have noticed that pine isn’t in the list of good exterior woods. Most pines don’t do well out doors, they don’t have the oils or cell structure to fight off decay. One exception being southern long leaf pine, as that was prized for mast building. An option is pine that has been pressure treated (PT). This is a process where the chemicals are forced into the wood cells under high pressure, thus preventing rot. The down side to using pressure treated wood is that is usually unattractive, heavy and, oh yeah, filled with chemicals. PT is great for structural work, but not a great choice for furniture work.

So now you know what woods work well outside. Are there others, sure? Lots of exotics work well outdoors as well. The problem with most exotics is that they are expensive, and not always harvested under, shall we say, the best intentions? But that is a blog for another day.

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