The three most widely available and suitable exterior lumber choices, not treated with chemical preservatives, include Western red cedar, redwood, and cypress. Your geographic location will determine the availability and cost of these materials.
Naturally Resistant
To deter the pests, homeowners can obtain heartwood-grade lumber for construction projects. Termites also tend to avoid specific species of trees such as redwoods, yellow cedar, Laotian teak, and cypress. However, these types of wood are not as long-lasting as treated lumber.
Cedar wood projects typically last more than 20 years without splitting, rotting, or warping. White oak and teak are also long lasting woods that are resistant to decay, twisting, cracking, or warping.
Choose Rot Resistant Wood for Your Project
Well-known domestic examples include cedar, redwood, old-growth cypress, mulberry, yew, osage orange, and black locust. Tropical wood examples include ipe, lignumvitae, purpleheart, and old-growth teak.
But building code dictates where you can use treated wood in applications — usually where there is risk of excessive moisture. Generally speaking, any wood used in outdoor projects should be pressure-treated.
Storing dry lumber outdoors should be avoided at all costs. The outside elements include water and drastic changes in temperature.
Using untreated wood for outdoor decks is not advisable because it is susceptible to rot and decay when exposed to moisture and other elements. Over time, untreated wood can become weak and unstable, posing a safety hazard for outdoor deck use or any other outdoor projects.
Which Wood Lasts the Longest? Teak wood easily lasts the longest when used for outdoor furniture or decking. When properly maintained, it can last for the entirety of your life and years after.
The best water resistant wood types & species. Iroko, Oak, Western Red Cedar, Cherry, Maple and heat-treated woods are just a few examples of timber that boast excellent dimensional stability and high resistance to shrinking and warping in the face of moisture.
Naturally resistant woods that are commercially available include black locust (Robinia pseudoacacia), teak (Tectona grandis), ipe (Tabebuia spp.), California redwood (Sequoia sempervirens) and bald cypress (Taxodium distichum). These have the highest resistance to rot over time.
While redwood or teak certainly qualify, five more common lumber species that also stand up well to sunlight, moisture and wood-boring insects are Western red cedar, Spanish cedar, cypress, white oak and mahogany. Red cedar tends to be knotty, but it's affordable and widely available.
Heirloom-quality handmade wood furniture should last more than a lifetime. In fact, it can last for decades if properly maintained. This type of wood furniture is more likely to reach the “antique” milestone, meaning it can last 100 years or more.
Wood that is naturally durable for decay and termites, as defined in IBC Chapter 2, includes the heartwood of redwood, Alaska yellow cedar, eastern red cedar, and western red cedar.
Juniper is a durable and incredibly rot resistant local wood that is harvested from grassland restoration projects in central and eastern Oregon. According to studies at Oregon State University, it lasts more than 30 years in outdoor, ground contact settings -- much longer than cedar or redwood.
Recycled Plastic Lumber and Plastic/Wood Composite Lumber
The plastics are rot- and corrosion-proof and don't crack, splinter, or chip. Even in exposed and sub-grade conditions, plastic lumber has a long life expectancy. It will not leach chemicals into the ground, surface water or soil as treated wood can.
Pressure-treated wood may be protected for a while, but if it stays damp enough for long enough and starts to rot, termites can feed on it.
There are three surefire ways to waterproof your wood for years to come. Use linseed or Tung oil to create a beautiful and protective hand-rubbed finish. Seal the wood with a coating of polyurethane, varnish, or lacquer. Finish and waterproof wood simultaneously with a stain-sealant combo.
Western Red Cedar is one of the world's most durable woods, as it has a natural resistance to moisture, decay and insect damage.
Teak. Teak is the most highly recommended material for wooden outdoor furniture among designers, not only due to its resilience in any season but also because of its style and soft, grained finish. This miraculous material produces its own oils, making it unique in comparison to other types of natural woods.
Since it's widely available, fir can be useful for those running a slightly tighter budget. It's one of the cheapest woods for outdoor use. If you're a woodworker or DIY garden furniture maker, this species also works and machines well, in addition to holding finishes easily — whether a clear varnish, stain or paint.
It is the world's oldest surviving wooden structure. Horyuji was constructed from Japanese cypress that were roughly 2,000 years old. It has been 1,300 years since the cypress were cut down, and the wood still stands firm.
With concrete holding the moisture against the wood, wood has no chance and will eventually lose the battle. Now you don't have to lose all hope because it's for certain that the concrete around the post will crack, therefore making it easy to pull out when it starts to rot.
Wood can Start to Rot in 1-6 months If:
Wood is untreated. The wooded area is sitting in water. Water and/or air space is hot & humid.
Cedar wood may last over 20 years when used in outdoor structures, such as decks, pergolas, gazebos, or furniture. It can last between 15 and 20 years when used for constructing a fence or support posts.