How Long Does Pressure-Treated Wood Last?
The life span of pressure-treated wood can be decades
Highlights
Pressure-treated wood is wood treated with chemicals to extend its lifetime.
Most pressure-treated lumber is preserved with various alkaline coppers.
With the right care, pressure-treated wood can last up to 40 years.
The main benefits of this material are affordability, durability, and versatility.
Wood offers endless home project opportunities, including building a deck, railings, and planters, but how long does pressure-treated wood last? The outdoor elements can take a toll on wood and make it look less than pristine. 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. Keep reading to learn more about the lifespan of pressure-treated wood and how to extend it as long as possible.
What Is Pressure-Treated Wood?
Pressure-treated wood is lumber that has undergone a pressurization treatment to increase durability and prevent decay, mold, insects, and water damage. This treatment utilizes a depressurized holding tank to remove excess air from the wood, and then replaces it with preservatives and water. If you hire a local deck builder to build your dream deck, they will help you choose the best type of pressure-treated wood for your project.
Best Projects for Pressure-Treated Wood
Depending on the application, there are two main types of pressure-treated wood: above-ground lumber and ground-contact lumber. For above-ground projects, you can use basic pressure-treated wood. But for ground-contact projects, like fence posts or landscaping, the wood is pressure treated with twice the level of chemical retention (and usually with the addition of saltwater) to help withstand the extra moisture.
Pressure-treated wood is ideal for projects that may require extra durability or fire retardation, including:
Decks
Framing
Porches
Fences
Railings
Sheds
Garden boxes
Landscape walls
Gazebos or arbors
Swings or playsets
Sandboxes
How Long Does Pressure Treated Wood Last?
Pressure-treated wood can last anywhere from 10 to 40 years, according to most manufacturers' guarantees. However, several factors come into play when determining the lifespan of the wood.
Maintenance
Maintenance is crucial for extending the lifespan of the wood. Proper upkeep can keep the wood in good condition for up to four decades. On the other hand, neglecting the wood can reduce its lifespan to an average of nine years.
Regular deck maintenance should include clearing snow and damp leaves to prevent rot, mold, and mildew, trimming grass and hedges, and periodically checking your home's drainage system. Additionally, applying a water repellent six weeks after constructing the wood and annually thereafter can help prolong its life.
Wood Type
The type of wood used is another important factor in determining the lifespan of pressure-treated wood. Pine, cedar, Douglas fir, and hem-fir are the species that best absorb the pressure-treatment chemicals, making them ideal for long-lasting woodwork. Pine and cedar are the most commonly used types of wood for deck framing.
Lumber Grade
The grade of the lumber is also relevant. #1 grade is a premium grade less likely to warp and has fewer blemishes and knots. It is often used for visible decking and railing projects.
In contrast, #2 or construction grade lumber is rougher looking and is typically used for framing and other non-aesthetic projects. #1 grade lumber is indisputably stronger, but it may need to be special ordered, as most hardware stores stock #2 grade.
Climate
Pressure-treated wood in sub-tropical or humid climates has a higher chance of rot due to the moisture in the air and contact with damp vegetation, trees, and shrubs. Therefore, pressure-treated wood in high-humidity areas like Florida should be treated for heavy-duty ground contact to maximize its lifespan.
Construction Use
Wood used in upright construction tends to last longer than wood used in horizontal projects because the upright wood is able to dispel moisture easier. In addition, wood posts that are set into dirt have a shorter lifespan than those set in concrete or gravel.
How to Extend the Life Span of Pressure-Treated Wood
Despite the various factors that dictate how long your wood will last—and some of them being out of your control—there are a few ways to extend the lifespan of your pressure-treated wood.
Dry It
Pressure-treated wood takes weeks or months to dry once treated. It’s important to wait out the allotted time before you paint, stain, or seal it. To see if it’s fully dry, sprinkle water onto it. Once the droplets absorb, you can treat or stain the wood deck.
Seal It
To keep your pressure-treated wood in tip-top condition, you should apply water-repellent sealers every year. And at the first sign of mildew, use a mildewcide cleaner. Together, these steps can help make your wood last longer.
Maintain It
Even pressure-treated wood needs regular maintenance. Remove snow and leaves as they fall to prevent rot and mildew. To help encourage the drying process, you can trim any vegetation away from the wood.
Benefits of Pressure-Treated Wood
Durable: Pressure-treated wood can withstand all types of damage, including regular use, wear and tear, scratches, and dents.
Rot resistant: The preservatives make the wood resistant to water damage and rot when properly maintained.
Affordable: Wood that is naturally more durable without pressure treatment, like redwood, can come at a higher cost. Pressure treatment allows for the same durability without the same price tag.
Insect resistant: The chemicals used in pressure treatment keep bugs away from your home and wood.
Versatile: Pressure-treated wood can be stained, painted, cut, and combined in various ways.
How Is Wood Pressure Treated?
The process for pressure treating wood has been drilled down to a science. The steps are very effective and controlled to ensure the wood meets all industry standards and building code requirements.
Lumber is placed in a pressure chamber where an industrial vacuum sucks any air from the cylinder and the wood. For woods that are resistant to penetration, like Douglas fir, manufacturers will make small incisions before placing them into the vacuum to help.
The chamber is flooded with the chemical mixture.
The chemicals are forced into the wood cells using immense pressure. The cycle time depends on the wood species.
The cylinder is drained and all excess solution is removed.
After treatment, the lumber is cured and dried enough for shipping (usually 24 to 48 hours). It will dry completely in sunlight after installation.
What Is in Pressure-Treated Lumber?
Historically, countries utilized various compounds and oils to treat and preserve wood, like olive oil in ancient Greece or tar in Rome. Today, most pressure-treated lumber is packed with a combination of various alkaline coppers, like:
ACQ (alkaline copper quaternary)
Copper azole
Micronized copper azole
Copper-HDO
Copper naphthenate
Borate
Polymeric betaine
For commercial uses, oil-type treatments are more common, like creosote or pentachlorophenol. But, these types of treatments usually leave an unpleasant odor or residue, so they’re usually reserved for places that won’t be touched often.
So, Is Pressure-Treated Wood Safe?
With all these chemicals listed, you may wonder if pressure-treated wood is safe. In the past, companies often pressure-treated wood with a compound called chromated copper arsenate (CCA). But in 2003, the Environmental Protection Agency and the wood industry decided to move away from making CCA-treated wood available for homeowner use because it may pose a health risk.
Today, everything on the market is deemed safe to use in projects like decks, children’s playgrounds, and garden beds.
Tips for Working With Pressure-Treated Wood
All DIY projects require safety precautions to prevent damage to you and your home. When working with pressure-treated wood, be sure to:
Wear protective gear, such as gloves, goggles, and masks.
Keep pets, children, food, and water away from the wood.
Always work with pressure-treated wood outdoors to prevent the copper coating from dispersing in your home.
Never burn pressure-treated wood, as the fumes can be harmful to you and the environment.
Use hot-dipped galvanized (HDG) or stainless steel nails, fasteners, bolts, and screws while working with pressure-treated lumber. The copper coating can cause regular hardware to corrode and fail.
Taylor Sansano contributed to this piece.
Frequently Asked Questions
Pressure-treated wood can not only be painted and stained, but it should be; doing so will help to prevent surface or deck board cracking. Allow the wood to dry out before painting it, as pressure-treated wood from the hardware store takes longer to dry than kiln-dried lumber. If water beads on the surface, it needs additional time to dry—in fact, it can take weeks or even months to fully dry. As soon as the wood absorbs water on the surface, it is ready to be painted or stained.
Various kinds of substances and deck preservatives act as protective coatings for wood to prevent rot, which is caused by water getting into the wood and creating cracks and splits. Stains, paints, and sealants are the three best options to protect your wood, but there are also oils, varnishes, and waxes available. You’ll need to reapply sealant at least once per year, and you should inspect your wood deck regularly to look for signs of damage or general wear and tear.
While the chemical, copper-based coating on pressure-treated wood offers protection from rot and pests, it’s not a silver bullet. An added sealant will help protect the wood further, though sometimes the wood is treated in a way that causes premature failure, and this is largely out of your control. It’s simply a case of bad luck. Regularly inspect all your house’s wood to look for any cracks or signs of mold and mildew. Getting ahead of the problem is the key to ensuring it doesn’t grow out of control.