Setting posts

[Rio_Grande]

I have a troubled privacy fence. The posts seem to lean no matter what I do. They were tamped in with dirt and have started to break at ground level. I am going to replace 17 of them this weekend. I have set a few in sack Crete, but many folks say not to do that as it will rot them. I was thinking about using gravel with lime in it, same as we use for road base but smaller.

What is the best way to set these 4x4 pressure treated posts? Have to stay put and prefer long life out of them.

 

[Sysop]

Dig your holes a foot deeper than you need, fill and pack the hole with stone allowing someplace for the water around the post to drain into. That keeps water from settling against the post and rotting it off. If you really want to get the most time out of them, line the hole with drainfield cloth so the stone doesn't mix with the surrounding soils and maintains the highest capacity possible. Then wrap the ends of the posts with drainfield cloth. That prevents the soil from making direct contact with the wood and provides a drainage pathway around the post down into the stone below.

 

[s219]

The building inspector here actually recommends some posts be backfilled with pea gravel or fine crushed gravel (#78 or #8). It will hold the post just fine and let water drain away (as long as the soil below drains; may not work with heavy clay soil).

Concrete would be OK if you can slope or dome the top of it so that water cannot collect next to the pole. My neighbor's gate posts -- untreated pine logs -- have been in the ground for decades with no rot. He actually set them right after sawing, when the wood was still green! Used dry mix, no water, then went back a few weeks later and put a cone of concrete around the post at ground level.

I copied him almost exactly, since I had some big pines to drop and needed gate posts. I dry set the posts with sacks of quickcrete and then put a sloped "hat" around the post with dry mix and watered it in gently. It set in place. No sign of problems, though it's only been 2 years. Check back with me in 10-20!

 

[Rio_Grande]

We have about 6 set in sack Crete. They broke off when it was wet and we couldn't tamp them in tight so I put a bag of quick creat in the holes tamped it in and they haven't moved. Just don't know how long they will last.

 

[AGRIMAN]

The best thing I have used is just dry sand. I don't use any of the dirt dug from the hole. Layer the sand in and pack as you go. If the ground is wet or the sand damp, I will add in some concrete.

 

[tman1020]

Make sure u use treated wood that is rated for ground contact not just standard treated there is a difference. Dig hole 3 times size of post set post in concrete. Trowl top of concrete to a dome. This was most common method in commercial application. additionally I would wrap post with roofing tar paper or something similar. Using the gravel pack or dry set concrete in my opinion is also a good option. I have had good luck with setting 4x4 posts in 9 inch holes backfilling bottom of post with existing dirt and toping off with 1 or 2 bags of dry concrete.

 

[EddieWalker]

The worse thing you can do it put gravel in the hole with the post. All this does is give water a place to sit.

Posts rot from the process of standing water slowly drying, then getting wet again and slowly drying. You want to keep the post as dry as possible and not create a place for water to stay any longer then possible.

If you have good clay soil, you don't need concrete. If your soil freezes, you need to be deep enough to be below the freeze line where you get frost heave. What happens is the ground gets saturated with water, then that moisture in the ground freezes and it either moves the post or pushes them up. Concrete works good in poor soil, loamy soil and sand.

Dig your hole, clean it out so it's all virgin soil on the sides and bottom. Put your posts in the hole, and get it level. Then fill with concrete so there is a mound at the top that allows the water to drain away. Just about every rotten post that I've ever seen is at the base of the post, where water sat after a rain or from sprinklers. If you fill with clay, compact it as it goes in and build it up to keep the water away from it.

With the new treatment methods of treating posts, 4x4's now twist and turn pretty bad. It might be worthwhile buying 50% more then you need, and let them dry out before starting. That should give you enough straight ones to proceed. Maybe.

Eddie

 

[texasjohn]

I have given up on treated wood posts...all methods of tamping in have resulted in rot and breaking off, over time. Your lean problem exists because the soil is moving as a plastic, slowly over time. The deeper you dig, the less it will move. To solve both problems, I recommend using metal posts and sinking them at least 3 feet. I suspect that the ones you are replacing were only 1.5 foot deep to start with. Use big U bolts to attach the posts to the wood fence.

Nothing else, IMHO, will last beyond a few years, like 5 to 10. Metal posts well sunk will last 30+ years.

 

[two_bit_score]

I have a troubled privacy fence. The posts seem to lean no matter what I do. They were tamped in with dirt and have started to break at ground level. I am going to replace 17 of them this weekend. I have set a few in sack Crete, but many folks say not to do that as it will rot them. I was thinking about using gravel with lime in it, same as we use for road base but smaller.

What is the best way to set these 4x4 pressure treated posts? Have to stay put and prefer long life out of them.

Try to get creosote treated posts if you can find some. Last bunch I found was in Seguin.

Looks lie there are two distinct schools of thought on the 'gravel at the bottom' theory. I never thought it was that great of an idea myself.

If you are going with typical treated posts try to buy them at a locally owned farm & ranch supply or lumberyard that knows what people have had good luck with over the years in your area.

Square posts do warp more than round posts.

Good luck on your project and let us know where you are located.

 

[Rio_Grande]

I am in southeastern Indiana. We have clay loam but this area has been back filled witch makes it layered odd.

The ones that are coming out are pressure treated, but they did not hold up, a couple broke off the winter after they were put in. The new posts are 4x4 rated for ground contact and purchased locally from a mom and pop hardware. I even asked what I needed even though I had a decent idea.

The old ones were put in by tamping the dirt removed from the hole back in. In the springs we have heavy rains that cause part of the ground to lay wet. When replacing one this spring there was about 2 foot of water in the hole. These that we are replacing are on higher ground and shouldn't lay that wet.

These are 8 foot post we set them 3 feet 6 in in the ground. That brings them out an inch or so taller than the nail rail on the fence.

When the ground was wet I have pushed these replacement 4x4 posts in the holes the old posts came out of and they have stood for a long time. The only reason I don't try that here is the existing holes are not straight. So I figure we will auger the holes.