The life span of your treated posts posts matters. Before spending thousands, or tens of thousands, of dollars on a fence it is nice to have a better idea of how long you can expect your investment to last.
So, to answer the question: How long will my treated posts last?
According to the Southern Pine Council you can expect properly treated posts to last many decades. They site a study by USDA Forest Service’s Forest Products Laboratory saying:
Test stakes of treated wood have been buried in the ground at various locations, stretching from the Mississippi Delta to the Canadian border. Data analysis indicates that CCA-treated Southern Pine stakes in place since 1938 have shown no failures at chemical retention levels of 0.29 pounds of preservative per cubic foot of wood, or higher.
Most treated posts are treated to a retention of .40 but you should always ask – just to be safe.
Here’s a great pdf from the USDA with expected life spans for various species of treated posts including a comparison of the life spans of treated and untreated posts (see page two).
If you want a guarantee that your posts will last you can get treated posts coated at the ground line from American Pole and Timber. I mentioned these posts before in How to Build a Fence that Lasts because I have seen them up close and they are tough. They claim that posts coated at the ground line with their poly coating will last fifty years.? In reality, the posts should last 150 years because the ground line is the source of infestations and the place where decay begins.? If that is protected, you don’t have much else to worry about.
The bottom line is that the life span of properly treated posts should be at least 20 years and can be easily extended to 50+ when installed and used in normal conditions (not in water or along the coast, for instance) .? If you choose the right materials, your grandchildren won’t even have to deal with building another fence.
I have a question about our wood deck. We purchased our home that was 10yrs old. It has a large wood deck. The deck is supported by treated 6 6×6 posts. To my suprise I find these posts are barried in some cases probable 5ft in the ground. I have dug down two feet or more and still did not find the bottom of the post. Should I be concerned about these 6×6 rotting and what kind of life span do they have barried in the dirt. Thanks
Hi Dan,
Good question. Someone built that right. 6×6 treated posts — if well treated — will last what seems like forever on land. With that, my first concern be about just how treated those posts are. Good luck finding that out unless someone left a treatment tag on the top (if that is accessible) or if the previous homeowner was exceptionally good at keeping receipts and left you the receipts for the posts.
Let’s assume they are properly treated to .40 or .60 with CCA (since they were treated before Dec 31st 2003). It should be reasonable to expect them to last 60 or more years. Factors that can shorten that are standing water around the post and wear and tear on them from weed eaters or other equipment. If you are concerned, you could dig around them like you’ve done and paint the area at the ground-line with some extra sealant or even with a plasti-coat similar to what you use to coat plier handles.
But, really, it sounds like you should not worry about posts and instead get a beer and kick back on the deck of your new home!
My condominium has a marina. Most of the pilings were installed about 1985. I am arguing that we need to replace pilings sooner than later, but some people seem to think pressure treated pilings will last indefinitely. Can you give me an idea how long we can expect pilings to survive in the waters of the Chesapeake Bay…about mid-way up the Bay.