How Long Does Pressure-Treated Wood Last

Woody Jackson | Last modified on October 7th, 2021

Pressure-treated wood is the common name for wood that has been treated with chemicals to reduce the risk of fungal decay and insect infestation. But, many people are interested, how long does pressure-treated wood last? It depends on different circumstances, but it can last for decades if treated and sealed correctly. Here, we look at what pressure-treated wood is, how it’s made, and some precautions to take when working with it.

How Long Does Pressure-Treated Wood Last

What Is Pressure-Treated Wood?

Pressure-treated wood is the common name for woods that have been treated with a chemical preservative. The most common type of preservative used in pressure treatment is chromate copper arsenate (CCA). CCA prevents fungal decay and insect infestation by replacing any moisture lost from within the timber. The chemicals contained within pressure-treated wood can also serve to retard the normal process of decay.

What Is Pressure-Treated Wood

Most pressure-treated wood is treated at a very low level of pressure: 1000 psi. Some pressures as high as 10000 psi are used, but this is for treating thicker material found in overhead and overhead-located structures such as bridges, buildings, and utility poles. 

These pressures are rarely necessary since the majority of pressure-treated wood is treated at 1000 psi or less. However, most timbers are treated at a minimum of 500 psi (psi), and some materials can be safely processed up to 3000 psi (psi).

Chemical Preservatives

Depending on the occasion you would like your wood to last, you will need to identify the appropriate preservative. In addition to the CCA preservatives, there are other heat-cured and cold-cured varieties available:

  • Copper Naphthenate – This will last the longest, but it is not very suitable for outdoor furniture or decking as it will turn dark. This will work for decks, fences, garden furniture, and storage buildings.
  • Copper Azole – This type of preservative is very expensive, but it is also long-lasting. The color won’t fade, and it is more weatherproof than other preservatives. This is best for decks, fences, outdoor furniture, and other places that will be exposed to the elements for an extended period.
  • Copper/Chromate – This is the cheapest method of treating pressure-treated wood. It is less durable than the Copper Naphthenate or Copper Azole types. However, it can last for up to 20 years and does not have to be reapplied after every application.
  • Copper/Chrome/Arsenate (CCA) – This is the most popular type of preservative because it is the least expensive and can last from 10-15 years without reapplying it. It is available at most local hardware stores, but keep in mind that they have restrictions on some types of wood that you should check with them first to be sure that they are allowed to treat it with this chemical. They also require that you reapply the sealer every two years.

Climate Considerations

The climate in which the wood is used will play an important role in determining the type of preservative you should use. Ideally, the best time to apply a preservative is in the spring when it is warm and dry out. This way, the chemical can soak into the wood and dry thoroughly.

The climate is also going to affect how often you need to reapply a new layer of preservative. If done at the wrong time or during inclement weather, not only will it take longer for it to soak into the wood, it may never do so correctly due to an abundance of moisture in the area. This could lead to rotting instead of rusting (or vice versa).

How Long Does Pressure-Treated Wood Last Outside

The duration that pressure-treated wood lasts outside will depend on some factors that can include how the wood is treated, what type it is, and environmental factors such as how it’s used. In general, if the wood is fully protected from weather and other elements, then it can last many years without any issues. 

How Long Does Pressure-Treated Wood Last Outside

The lifespan of pressure-treated trees is really based on several factors, which make a huge difference in the length of time pressure-treated timber will last outside with or without proper care. For example, water contact can cause the wood to rot in a short period.

How Long Does Pressure-Treated Wood Last In Concrete

Wood treated with preservatives is quite durable, but it is still important to know how long it will last in concrete. If you are thinking of using pressure-treated wood for your next project, you will need to know how long the wood lasts in concrete, and here are some factors that may influence its lifespan.

Before you start, it is essential to find out if the wood is treated with preservatives. If not, pressure-treated wood will last only a few months in concrete, while treated wood will last for decades.

FAQ

How Do You Keep Pressure-Treated Wood From Rotting?

The best way to keep pressure-treated wood from rotting is to store it in a well-ventilated, dry place. In addition, the wood should be kept away from direct sunlight, and the bottom edges of the boards should not touch each other or concrete.
If the wood is moist, the surface can be lightly brushed with a tack cloth if it’s not too dirty. If there is any mold or mildew on the wood, this should be cleaned off as well.

Does Pressure-Treated Wood Need To Be Sealed?

Most manufacturers recommend sealing the surface after painting over the treated wood surface if you plan on painting over the treated wood surface. As a general rule, it’s worthwhile to seal treated wood if you plan on repainting and an area of significant use or wear in the deck.

Will Pressure-Treated Wood Rot If Buried?

Underground wood can rot or not rot. The type of wood and soil, water pH, the type of fungus present in the area, whether the underground has an adequate drainage system, and even how long it’s been buried are all factors that affect how quickly or slowly a piece of pressure-treated wood will decay.
A timber is likely to be hardy for at least three years if it’s buried 6 inches below grade with a good drainage system. If you want it to last longer than that, it should be placed in an 18 to 24-inch trench with good drainage and then covered with topsoil if possible. Just don’t let any rain or runoff pool around your timber.

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