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.
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.
Redwood and Cedar. While pine is the best exterior softwood for the money, Redwood and Cedar are better exterior softwoods for stability. Redwood and Cedar are pinkish, with heart redwood being a darker pink than Western Red Cedar.
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.
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.
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.
Some species of wood are naturally rot resistant due to complex chemical compounds that they evolved to protect themselves against decay. Well-known domestic examples include cedar, redwood, old-growth cypress, mulberry, yew, osage orange, and black locust.
Oak. Oak is another hardwood species well-known for its water and rot-resistant properties. It is a popular choice for outdoor projects such as decking, fencing, and furniture due to its durability and resistance to decay. Oak wood has a high tannin content, making it naturally resistant to moisture damage.
While similar to standard exterior plywoods, marine plywood is the highest quality (AA, AB, and BB), constructed from wood without knots. Eliminating the knots in wood improves durability because it practically eliminates the possibility of water pockets forming within the wood.
Some say that untreated 2×4's can last up to two years before showing signs of rot and others say it can last even longer. When deciding if you should you use an untreated 2×4 it depends greatly on the application, how much weather and sun it's exposed to and if it's making ground contact.
Storing dry lumber outdoors should be avoided at all costs. The outside elements include water and drastic changes in temperature.
Cypress, redwood, and cedar are three softwoods that have natural moisture-wicking properties and make fine choices for outdoor furniture.
Cedar wood projects normally last more than 20 years sans any rot, split or warp. Among other water resistant wood types are White oak and teak. These are also long lasting woods resistant to warping, decay, cracking, or twisting.
Liquid sealants are one of the most common ways to waterproof wood. These sealants are applied directly to the surface of the wood and form an impermeable barrier against water penetration. It is important to apply several coats of sealant to ensure a thorough application.
Specific Areas to Check for Rotting Wood. Over time, rain can repeatedly soak window frames and sills, causing damage and, eventually, rot.
Sealing your outdoor wood once or twice a year - depending on your climate conditions - is important to maintaining the quality, and re-staining helps maintain its style. You could even try different colors of stain for a different look each year.
Paint protects the wood and also seals the tiny cracks and gaps that you might not even know exist in your building's exterior. These small blemishes start to get bigger if they're left without any treatment. Sooner or later, you'll have to deal with a much larger and more expensive problem.
Tight grain, solid timbers are the best option for timber floors in wet areas as they can withstand moisture. Examples of these timbers are cedar, teak, mahogany and locally grown bamboo. Timbers not suitable for wet areas will hold in the moisture, and expand, warp and lift as the timber dries.
Waterproof flooring stands up to water, resisting any damage from it, but it still may be susceptible to damage from pH extremes introduced to the water. On the other hand, flooring labeled as water-resistant handles common liquid spills but offers little protection from water and the duration of exposure is critical.
Key point: Any of these woods, whether teak, oak, cypress, cedar or redwood, is not uniformly rot-resistant. The outer wood, called sapwood, often has minimal or non-existent rot-resistance properties. The darker heartwood has the good stuff in it – organic materials commonly referred to as extractives.
Tips for Preventing Wood Rot
Always use decay-resistant or pressure-treated lumber for decks. Wood that touches the ground should be pressure-treated lumber that's rated for ground contact. When building an exterior project with wood, stain or paint all sides of each lumber piece before assembly.
Pine does not naturally resist decay, and it is pressure treated to make it more durable outdoors. So cedar gains a bit here with its natural character contributing to its durability. Pine is still a good choice for outdoor furniture, it just doesn't naturally resist the elements as strongly as cedar does.