Though decks can be made from all different kinds of materials, the overwhelming majority of decks – in America, anyway – are still made from pressure-treated wood.
Strong, durable, and reliable (not to mention affordable inconsistent), pressure-treated materials are beloved for their longevity. It isn’t at all uncommon for deck posts (and other PT components on a deck) to go 10, 15, 25, or 30 years before needing to be replaced.
Yes, you’re reading that right.
A properly built pressure-treated deck – with pressure-treated posts – might last a whole length of your mortgage (and then some).
How Long Will Pressure Treated Deck Posts Last?
There are a bunch of different factors that conspire together to determine how long your pressure-treated deck – and your PT deck posts in specific – will last, but it isn’t at all unusual to get multiple decades out of these construction materials.
Pressure-treated wood today is incredibly safe and engineered to last longer than it ever has before.
With the right design, careful construction, and a little bit of routine maintenance (something we touch on a little more in depth in just a moment) it’s not hard to imagine pressure-treated deck posts lasting 15 years, 25 years, 35 years or longer.
In fact, under ideal conditions the American International Forest Products organization believes that pressure-treated posts could give you 40 years of utility without any rot, decay, or degradation.
Some pressure-treated post companies say you could squeeze 70 years of utility out of your PT deck posts if you were particularly careful with upkeep!
Now, obviously 70 years out of a wooden deck – pressure-treated or otherwise – is a bit of a moonshot.
The chances are pretty good that you’re going to have to do some repair and some replacement before you hit the seven decade mark with your deck.
But getting 10 to 20 years out of your deck posts without ever having to worry about them?
That’s pretty much par for the course!
Pressure Treated Wood 101
The secret to the longevity of pressure-treated wood is the process (the chemicals) that go into its production.
Pressure-treated materials are made from lumber that has been placed inside of a depressurized holding tank. The idea here is to remove excess air completely and replace it with a chemical bath specifically designed to protect the wood from rot and degradation.
That chemical bath is flooded into the tank, the pressure cranked up, and all of those chemicals are physically forced into each and every fiber of the material itself.
Usually PT material is made from yellow pine from the south (a material that really takes to pressure-treated processes), but other materials can be used as well.
The end result is a wood that is a little bit denser but otherwise a material that is just as easy to work with.
Oh, and it has the ability to withstand the rigors of completely “raw” exposure to external elements even in some pretty harsh climates.
Pressure-treated decks are designed to last in the Pacific Northwest as well as the sunbaked climate of Arizona just the same as they are being hammered by seawater in the Northeast or swallowed up in the humidity of Florida in the summer.
These deck posts are built to last!
Is Pressure Treated Wood 100% Rot Proof?
While PT deck posts are resistant to rot, they aren’t impervious to breaking down over time.
Yes, it’s going to take a whole lot longer for your pressure-treated deck posts (even those that have been buried underground to act as a foundation for your deck) to start to “fall apart at the seams” – but it is going to happen somewhere down the line.
A handful of things can either speed up or slow down the degradation process.
For example, pressure-treated deck posts that have been sunk into dry, stable soil with excellent drainage aren’t going to break down or rot anywhere near as fast as pressure-treated deck posts – identical deck posts – sunk into wet, poor drainage soil.
That long-term exposure to those less than ideal (and particularly soggy) conditions is going to take its toll, sooner rather than later.
Pests – like termites – can do a number on pressure-treated materials over time as well.
It’s not just that termites will bore little holes into the wood and eventually compromise it structural integrity, either. They will do that for sure, but they also allow water to penetrate deeper into the wood fibers of pressure-treated material through those little wooden tunnels as well.
Get some freezing temperatures with water stuck inside those tiny little tunnels and you get rapid expansion, splitting and cracking your PT boards anywhere water is trapped.
Sometimes you’ll also get bacterial and fungal growth inside of your PT boards (particularly deck boards that are down low near wet, soft ground areas) that can overtime compromise your boards as well.
Pressure Treated Wood Upkeep Tips
To really extend the life of your pressure-treated deck boards it’s a good idea to apply a quality stain specifically designed with this material in mind.
Because PT boards are going to come “stained” a yellowish green straight from the factory (a result of the chemical bath needed to create pressure-treated material) you’ll want to go with a darker color.
Oil based stains are best when you are working with pressure-treated deck posts. The oil will wick into the wood better, won’t compete with the pressure-treated materials designed to repel water, and will provide a better barrier against moisture.
Secondly, it’s important to regularly clean your pressure-treated deck posts at least every six months or so.
You don’t have to go crazy here. A quick blast with a pressure washer and maybe a little bit of wood cleaner applied to the surface of your deck posts and beams usually tackles the job pretty well.
You might need to let your PT parts dry for 24 hours or so before you make a second pass with the cleaner and the pressure washer, but that’s about all it takes.
Finally, it’s a good idea to get out in front of any pressure-treated deck parts – especially posts – that are starting to show signs of wear and tear before the problem is a real emergency.
Regularly inspect your deck a handful of times a year so that you know what kind of condition it’s in all the time. Repair parts that can be repaired and replaced parts that need replacement and you won’t have to worry about deck catastrophes.
Closing Thoughts
Just how long will a pressure-treated deck post last?
Chances are good that you won’t have to rebuild your deck (more than maybe once) over the life of a 30 year mortgage.
Not bad, right?
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