A pressure-treated deck could last as long as 50 years with regular maintenance like yearly sealing and staining. But the average pressure-treated deck will last 15-20 years.
Below, I’ll explain the longevity of most pressure-treated wood decks, diving into the factors that may cause sooner replacement. I’ll also explain why pressure-treated wood tends to rot over time, despite its protection from the elements. Keep reading to learn more.
Why Build a Deck from Pressure Treated Lumber?
When most homeowners start drawing up plans to build a backyard deck, they have many options available for materials. Although composite and PVC decks benefit from way less maintenance, a lot of homeowners prefer wood decks for their lower initial cost.
Depending on the brand and profile but initially, a pressure-treated deck will cost a third of the price of composite decking. Compared to the higher-end PVC decking, a pressure-treated deck could cost one-fifth the price. Making pressure-treated decking a bargain.
However, wood is very susceptible to rot from moisture, especially when located outside and exposed to the weather. Despite pressure-treated wood being treated for termites and fungus, it will still weather outdoors. Being especially vulnerable to water.
For backyard decks, the most common choices are lumber treated with copper, which comes in various forms.
- MCA (micronized copper azole)
- CA (copper azole)
- ACQ (alkaline copper quaternary)
Source: US Forest Products Laboratory
But there are many different types of pressure-treated wood available. All are treated to minimize rot, making them ideal for outdoor projects like a backyard deck.
Building a deck from treated wood increases the deck’s longevity, cuts down on maintenance, and saves one money in the long run.
Factors that Contribute to How Long a Pressure-Treated Deck Will Last
This is where I answer it depends. How long a pressure-treated deck lasts is mainly dependent on 4 things.
Location of the Deck
This includes the bigger region in which you live and the deck’s location in relation to the house.
A deck built in a wet climate like Vancouver with its almost constant rain, 193 days in a year the wood will almost always be wet. With water being the number one reason that pressure-treated wood rots. You cannot expect the deck to last as long compared to Calgary, where we have 333 days of sun.
The location of the deck on the property will also make a difference. South-facing full sun decks will require more maintenance to last as long as a slightly shaded north-facing deck. But again, if that shaded deck is very moist, that can cause premature rotting. Especially mould growing on the decking.
No tree is alike, nor is the wood harvest from them. A deck built with better quality wood will last longer. Something to consider, cheap is nice but only if it lasts. You want at least #2 or better wood.
The level of treatment should also be considered. Wood with a higher level of treatment stands a better chance of lasting longer than barely treated wood. Often this means installing wood that is treated for ground contact, which has twice the amount of treatment as above-ground pressure-treated wood.
Distance From Ground
Even distance from the ground will impact how long the deck will last. Even with ground contact wood, the additional fungi in the dirt can rot the wood.
Also, lower decks often have poorer ventilation than raised decks which increases the potential for rot.
A well-built deck will always last longer than something haphazardly thrown together. A wood deck built with the proper slope and under deck drainage are just to name a few things that will increase the deck’s life.
Next to the decking, the joists are something that care should be taken to install correctly. I have gathered 15 Ways to Prevent Joists from Rotting
This one should probably have been first, but maintenance is the single biggest reason for wood deck failure. Despite being treated, wood decks need to be maintained. This includes regular cleaning, annual staining and sealing.
Without these, a treated deck will not last much longer than an untreated deck. Okay, I take that back, but it will seriously limit its lifespan.
If you are not willing to stain your deck regularly, you are better off checking out some of the many composite decking brands. Which require minimal maintenance and will last a minimum of 25 years, but many are warrantied for even longer.
Will Pressure Treated Wood Rot Over Time?
Even though pressure-treated wood is designed to last a long time and survive various weather cycles, it can still rot. Nature has its own agenda. And just as anything else can become susceptible to rain, wind, ice, and other elements, pressure-treated wood will expand and contract as it wets and dries, leading to cracks and imperfections.
These imperfections lead to vulnerability, and over time, will cause rotting that can speed up and get out of control if the deck isn’t maintained.
Additionally, pressure-treated wood is especially vulnerable on the ends of the boards where the grain is exposed and any areas where nails or screws have been inserted. These tiny holes and cracks can let in water and lead to more rot.
Both can be resolved during construction.
End-treatment is a must when building a deck with pressure-treated wood. Buy a can and a brush and treat every cut as your build the deck. Problem solved.
For the screws, this is one of the reasons I recommend Camo edge screwing. With the screws installed on the edge of the decking there is no collecting of dirt and water on the decking in the screw heads. Problem solved.