Pressure Treated Timber protects against timber rot and insect damage, but it is not infallible. Builder Tim Carter explained in this Washington Post article that there are several reasons pressure-treated timber can deteriorate quicker than expected.
The best way to protect and preserve wood, including timbers that have been tanalised or pressure-treated is to use a wood preservative. A neglected garden shed that has been allowed to rot and decay.
If you are not diligent about the care and maintenance of pressure-treated pine, it will change color, crack, warp, and cup. Depending on the weather and environment where you live, it may also be susceptible to mold, rot, and insect damage.
The truth is, treated lumber can — and does — rot.
Pressure-treating can make wood water-resistant, but it's not 100 percent rot-resistant. Any time the wood moves, bends, or cracks, water can enter. While this may seem worrisome, the key is to keep the water away.
How Long Does Pressure-Treated Wood Last? It depends on the climate, the type of wood, its uses, and how well it's maintained. While pressure treated poles can stay up to 40 years without any signs of rot or decay, decks and flooring might only last around 10 years.
Once installed, pressure treated lumber can last for many years submerged in water, and unlike steel it is not vulnerable to corrosion or electrochemical reactions, and it can last as long or longer than naturally moisture-resistant wood species.
Due to the rate at which pine grows, it is proving reliable in meeting demand. Compared to merbau, treated pine still has great longevity, lasting between 15-20 years.
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.
Pressure treatment helps protect wood from rot and insects with the help of high pressure and preservatives, helping to extend its life. Generally, pressure-treated wood can last anywhere from 10 to 40 years, depending on a few factors.
When it comes to comparing treated wood vs. cedar, pressure-treated wood is the sturdier and more weather-proof of the two. It's highly resistant to insect attack and rot, and special versions rated for “ground contact” can be buried in soil and will continue to shrug off decay for decades.
In fact, treated pine posts are said to last for 15 to 25 years, while hardwood posts last for 20 to 30 years. All of this means that if short term costs are your limiting factor, then treated pine is your best bet. If aesthetics is top priority, then hardwood is the way to go.
Painting of the treated pine will also assist with reducing any potential for dislodgeable arsenic, further protecting you from any potential hazard.
Although treated wood is protected against decay and termite attack, the application of a water-repellent sealer to all exposed wood surfaces is recommended upon completion of construction. This sealer will help control surface checking (splitting or cracking) and provide an attractive appearance.
Answer: Treated pine is dipped in preservatives prior to sale when applied to outdoor applications. However, this process will not stop the timber from requiring maintenance. You should seal and oil the deck annually with appropriate preparation.
In certain conditions, even pressure-treated wood can rot and decay. Moisture and pooling water on decks can lead to rot and decay. Because dry rot is a fungus, it can spread like a cancer throughout a deck. Dry rot is caused by microorganisms that eat the cellulose from the wood leaving it brittle.
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.
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.
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.
If you're looking to make a lengthy investment, consider the fact that cedar fences will stand, with no maintenance, for up to 25 years. Meanwhile, pressure treated pine last up to 15 years, provided you are regularly maintaining it.
Treated Pine is timber that has been permeated with a chemical solution, giving it a long-term resistance to decay, insects, and other deteriorating factors. This effective and lasting protection enables timber to be used in many applications including pergolas, decks, cladding, retaining walls, posts, and poles.
Treated pine is classified according to durability, with H3 and H4 being the more durable classifications for external use. H3 is the best option for all your subframe work above-ground, while H4 can be used for posts and other things that are close to/touch the ground or need to be dug into the ground.
While a treated 4x4 may last 10 to 25 years, depending on the wood, the soil, and weather conditions, following the simple steps below could double or triple that number. By comparison, an untreated wood fence post may need replacing in as little as five years.
Ground-contact lumber is, as the name suggests, suitable for contact with the ground. It's commonly used for pressure-treated posts and some framing. Containing a greater amount of chemical treatment, these wood products can last much longer than aboveground lumber, and up to 40 years, in some cases.
Pressure treated wood can crack and split from water exposure and this will allow fungi to get into the cracks and create wood rot. If you have a pressure treated deck this can be a harder problem to avoid. The best way to protect from pressure-treated wood rot is to apply a deck preservative.