Ipe Wood. Ipe wood can last up to 50 years outside without needing replacement. This wood has become more popular within the last 10 to 15 years and is known best for its tight grain, reddish-brown color, strength, and durability.
For example, Teak doesn't need any treatment which prolongs its lifespan because it is naturally durable and doesn't have much movement whereas kiln dried Oak does need treating to prevent it from: Losing moisture and shrinking in the summer.
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.
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.
Untreated Wood
Left in their natural, unfinished state, most woods deteriorate quickly when exposed to outdoor environments. However, there are several species that have naturally occurring chemicals that help them shrug off harsh weather and insects.
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.
Use an outdoor-rated finish like polyurethane, epoxy, lacquer, or varnish. Make a natural oil finish with one part tung or linseed oil, one part mineral spirits, and one part polyurethane. Use a stain sealant combo that gives your wood some color and a durable finish all in one.
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.
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.
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.
Extremely Rot-Resistant Wood
Mahogany – This is the king of hardwood. It is extremely dense and hard which keeps the insects and water at bay, preventing rot. Mahogany is beautiful when finished natural, which is why many doors are built with it.
Moisture Resistant Flooring Materials
Naturally decay-resistant wood subflooring (redwood, cedar, some oaks, bald cypress).
Minwax® High Performance Wood Hardener is a quick drying liquid formulated to strengthen and reinforce decayed or rotting wood. Minwax® High Performance Wood Hardener 4.3 out of 5 stars.
If you're looking for a durable, long-lasting material that's resistant to rot and decay, cedar is a good choice. Cedar is more expensive than pressure-treated wood. Cedar has a more natural look that many people find appealing.
Burns well but has a tendency to spark. Birch burns easily and can be burnt unseasoned. It also burns very quickly so is often best mixed with a slower burning wood such as Oak or Elm.
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.
Redwood, cedar, black locust and black walnut.
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.
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.
Boric acid (borate) is one of the most effective fungicides for use in treating wood rot. It can be applied to wood during construction to prevent future rot, or as a treatment to stop an active decay fungus from growing.
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.
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.