Pole longevity

[rd_macgregor]

I hope to get an outbuilding or two under way next summer, but, like many pole barn neophytes, I worry how long the "foundation" will last before rot takes out the whole building. Now, I realize I'm rehashing a recurring theme, here, but I wondered about ways to increase the likely longevity/rot resistance of pressure-treated poles. Would painting the pole lower end with some sort of additional preservative help? I've also seen advertised plastic sleeves to go over the buried part of the pole and isolate it from ground contact. This got me wondering if heavy (eg several layers) shrink-wrap plastic would accomplish the same thing?
Any thoughts or suggestions?
Bob

 

[flyerdan]

The thing I'd worry about in wrapping them in plastic is that it would hold in any moisture that found its way inside. Years ago my dad built a pole boat shed and had the last six feet of the posts treated with penta so that the 4 or 5 feet in the ground would be preserved. Don't know if there is a local place that can dip poles for you, but it might be worth looking into.

 

[adventure bob]

Definately dont want to wrap as it will trap moisture and make the problem worse. You want to promote quick flow away form the poles. Ours have sand, washed gravel and filled with roadbase. The poles themselves are engineered with the bottom 6ft being direct water contact rated. Should last longer than Im alive.

 

[Josh Shoemaker]

Paint the bottom 3 foot of the poles in burnt/used motor oil. Just keep putting as many coats on as it will absorb. I have painted a pole barn that I built with used motor oil. It works great, looks like stain, keeps carpenter bees, and is water repellant. Don't wrap it in plastic. You want water moisture to be repelled and if water got in with the plastic it will sit there and rot out the post prematurely.

 

[Budweiser John]

If I were building a post building today I would use the "permaPost" system. Basically a concrete post with a wood pole attached above grade. I have one post building about 40 years old that is still serviceable but have replaced some posts along the way. I have another building, a "Wick Building" that was built in 1983 and the posts are all but shot.
Now that the EPA has gotten in the act, I would not expect a buried post to last more than a couple decades. Wood and dirt just don't mix.

 

[quicksandfarmer]

If I were building a post building today I would use the "permaPost" system. Basically a concrete post with a wood pole attached above grade. I have one post building about 40 years old that is still serviceable but have replaced some posts along the way. I have another building, a "Wick Building" that was built in 1983 and the posts are all but shot.
Now that the EPA has gotten in the act, I would not expect a buried post to last more than a couple decades. Wood and dirt just don't mix.

Here's a link: https://www.permacolumn.com/

 

[SPIKER]

you can use some spray on treatment on the bases (end going into the ground) but most of the rot will occur at or near the soil-air point. Below Grade will not rot much if at all and above grade will be same as long as it remains mostly dry. Like others have said many options but will always be different opinions and options depending on soil conditions. Best to use some gravel at and below grade with native soil tightly compacted in around the post after everything is set...

I ended up going thru a few extra steps for my mail box that I took a 6" PVC pipe used a garbage bag. I lowered the post into the lined PVC and poured used motor oil into it. It sucked up about 2 quarts of oil over a couple weeks. the tube was 3 or 4 feet of the 4x4 and is planted with about 6" of the oil soaked end above grade. That was about 8 years ago and not a bit of noticeable rot..

Mark

 

[EddieWalker]

You don't have to do anything to protect the poles in the ground. If they are rated for ground contact, they will be fine long after you are gone. Posts rot out at the surface of the ground from water sitting there, and then evaporating. The getting wet and drying cycle is what breaks down the wood and causes the rot. The secret for longevity in a pole is to keep it dry. For fences, you have to build up a ramp at the base of the post to shed water away from the post. For barns and outbuildings, you need to have the water flowing away from the building as quickly as possible. The walls also protect the posts, so if done right, there should never be any water contact with the posts.

For posts, I would only use 6x6 treated posts. The smaller ones are too prone to warping. Some places like to use three treated 2x6's because they feel they are straighter and will remain straight. They are also easier to notch to support the trusses because you just cut one of the boards to length and then you have your rest. The problem is that it's VERY HARD to find 2x lumber that is rated for in ground contact. You can't get it and Lowes or Home Depot, and you ABSOLUTELY have to have it if you expect it to last.

Eddie

 

[rd_macgregor]

Interesting suggestions. I presume that you would also save a bit with the concrete post construction since you'd not have to buy tall PT poles...most of which wouldn't ever be in contact with the ground, anyway. So, what is the cost difference between a 16 ft PT 6x6 pole and a 12 ft non-PT 6x6 + permacolumn?

 

[s219]

Around here, posts are set in gravel so that water cannot collect around the edge where it meets the ground. It assumes the bottom of the hole can drain, of course, which may not be true for severe clay.