Many factors go into the longevity of pressure-treated wood, but pressure-treated wood typically lasts anywhere from 10 years to upwards of 40 years.
If you’re building a new outdoor deck for your home, you’re wisely weighing your options by asking yourself, “how long does pressure-treated wood last?” You can use pressure-treated wood for everything from the joists to the posts, but certain elements may last longer than others.
Here’s a closer look at what you need to know about using pressure-treated wood for your new backyard deck.
Factors in the Lifespan of Pressure-Treated Wood
Pressure-treated wood undergoes a treating process that makes it last longer than lumber alternatives.
Wood is put in a holding tank that’s depressurized. The air is extracted and then replaced with a chemical solution, commonly copper, arsenic, and chromium. That solution is incorporated deeply into the wood.
Because of this preservative, the wood resists rot and therefore resists insects who thrive on rotted wood. The chemical seals pores, further preventing boring insects from taking up residence.
A sealer that’s a water-repellent should also be applied, helping the wood repel moisture. This is not done at the mill where wood is treated but should be done after construction.
While overall pressure-treated wood is designed to last longer than other types of lumber used in decks, there are many factors that will impact exactly how long the pressure-treated wood you use lasts.
The specific type of chemical preservatives used and how deep it penetrates is a big key to the wood’s lifespan. Wood is often incised to increase penetration. This is very common with ground contact pressure-treated wood but not exclusive.
Wood is still treated with chromated copper arsenate (CCA) in heavier applications, but for lighter-duty applications, wood is frequently treated with a copper azole, amine copper quat, or ammoniacal copper zinc arsenate.
Climate is also a key factor. If you live in a wet, humid environment or one where harsh winter weather is prevalent, your pressure-treated wood may have a shorter lifespan due to regular exposure to natural elements.
In tropical climates, pressure-treated wood lasts longer if it is specially treated for ground contact. Moisture-rich or acidic soil can also cause faster deterioration in deck posts.
Main Types of Pressure-Treated Lumber
Not all pressure-treated lumber is created equal. There are two main types typically used by contractors and homeowners alike: above-ground lumber and ground-contact lumber.
Pressure-treated above-ground wood should be used outdoors for elements that are at least 6 inches (150mm) above the ground. These would include joists, deck railings, and deck flooring.
Higher chemical combinations are used in ground-contact wood since it protects it more efficiently against damage caused by rain, vegetation, and other decay agents. This is used when the wood contacts the ground or is installed less than 6 inches from the ground.
Woods to Consider
The type of wood you choose for your backyard deck project will also impact how long it lasts. Some woods are better suited for pressure treatment than others, such as southern yellow pine. Additionally, some woods, such as cedar, are also more naturally resistant to decay and rot.
For deck framing, pine and fir are commonly used, especially Southern pine in the eastern United States and Ponderosa and red pine in the northern United States.
Southern pine’s logs absorb pressure-treatment chemicals exceptionally well since they are high in sapwood. In the western United States, Douglas fir is considered a good pressure-treated choice. Hem-Fir is another species in the west that preserves very well.
Maintaining Pressure-Treated Wood
Using pressure-treated wood alone does not ensure that it will last. Any wood will last longer if it is effectively maintained through sanding, cleaning, and sealing surfaces. Those approaches will go a long way in preventing you from having to replace your desk every decade or so.
Experts recommend using a water repellent on decks six weeks following completed construction and then yearly. Regularly inspect your desk to look for wood failure or corrosion that can loosen bolts, nails, and screws.
Replace wood that shows any sign of decay and rot. Another approach: applying and reapplying weather-resistant stain when it is needed.
And speaking of weather, you can also clean your pressure-treated wood, especially if you live in humid conditions.
Look for a product that contains a mildewcide to prevent mildew from taking over. An ultraviolet stabilizer will combat decay due to long sun exposure, making the deck last even longer.
Whenever you wash pressure-treated wood with a cleaner, let it dry, and then seal it with a water repellent. You can rest assured that you’re doing your best to keep your pressure-treated wood in the best shape for a long life.
For outdoor projects, building with pressure-treated wood will increase how long your project will last. Making using pressure-treated wood essential for lasting exterior wood projects.
But treatment is only one of many ways to prevent deck joists from rotting. The effectiveness of each will vary in increasing how long the wood will last, but all will increase the life of your deck.