Setting fence posts in cement.

That said, good ideas for post vary around the country/world. Alot depends on your climate and soils. The best advise I can give you, not know'n where you live (guess'n Maine buy your handle, so if so I have no idea what works!!) would be to look around. Find an old fence row in the woods some where where the old woven wire has rusted away. Dig down and see whats under it. You could find the oldest farmer in the area who is friendly and ask what he has seen work best over the years.

Good luck.

Dave

I'd not bother with cement unless you're securing or retaining a load. Or this is a residence.

I put up wood fence for a living. I've installed so many 4x4 posts I'll be doing it for 20 years after I'm dead just out of habit.

When you dig your hole just bell out the bottom some so it can't heave. Whenever you set ANY wood post in concrete never seal the bottom in concrete. Set your post in the hole and add 6" or so of gravel or sand. Anything so you don't seal up the end of the post. When you pour the concrete slope it downward slightly so you get a bit of runoff and the post won't sit in water.

I have installed miles of residential fence as well as myriad jobs for the government in parks, airports and such. There is usually some good advice on this site from knowledgeable people and sometimes not so good information. Take it as you will.

Why don't you seal up the end of the post or are you just saying don't seal the end in concrete which will then make the post retain water?

What part of the country are you in and what type of soil do you have?

What specs is the gov using when putting these fence projects out for bid?

How do your posts look after you have taken them out after 20 years? or have you taken any back out?

I have trouble digging a bell bottom with a spade and then cleaning out the hole after initially augering the hole or even when using a hand post hole digger. How do you do it?

Also wondering what you think of these new ACQ treated posts for direct burial? How do they compare to CCA? I just got some round fence posts for TSC that are still .40 CCA that I'm getting ready to use in a corral. I suppose all the 4x4 posts bought now are going to be ACQ.

I'd also like to know how you get your posts in a straight line on a long run both at the top and the bottom. String line or laser or something else?

If you use T-posts how do you drive them? I've been thinking of making/converting a log splitter to drive some steel posts.

Thanks, it is always nice to hear how the big contractors do things.

I bury the posts 3' deep on a 6' spacing. I paint the bottom 3' of the post and end with asphalt foundation coating which helps keep the water, termites, and stuff out. Dig the hole a few inches deeper and put a few inches of rock in there. Unless there is a pile nearby, I just get a couple bags of lava rock. Then back fill with fill sand. Leave extra sand piled around the post. Add more a year or two later.

I have taken out many a old fence post. Concrete in clay doesn't work cause you can never really bell shape the bottom of the hole. Frost heave just pushes them out. During the summer, the clay shrinks and pulls away from the concrete, then the wind just works the fence so hard that it wallows out the holes and the fence with the post, concrete, and all blows back and forth in the wind. With sand, as the clay shrinks, the sand just moves with it into the clay and packs tighter and especially with any wind working on the fence. I have had posts that I broke the concrete off and they looked like new and then some where the concrete allows the water to sit on top of it next to the post and the post rots off right at the top of the concrete. Combined with the 6' spacing where we get a lot of regular 30 to 40 mph winds, my fence doesn't budge. I also lean my cedar fence boards up against a fence for a week to dry them and preshrink them before screwing them on without any spacing between or else just start the screws and come back in a couple weeks to get my final spacing. They will still shrink a little more yet. Burying a 8' post down 3' still leaves 5' sticking up for the top 2x4 runner for the fence. I put all the runners on before I backfill around the posts to get everything square and level. I also like to lay a course of 6" by 12" colored concrete bricks that are 1" thick between the posts which makes a nice mowing edge and then place the fencing an inch or two above it.

Anyway, it works for me.

My grandfather used to look at me as if I was pathetic at putting fenceposts in.

The old saying goes "if you filled the hole up and still have dirt left over, you ain't tamping hard enough."

My grandfather not ONLY put in all the dirt that came out of the hole, but also had to go get MORE dirt from elsewhere.

Damm things would be tight for 20 years.

Concrete forms through the reaction of calcium silicate and water. As soon as the cement paste gets wet, the calcium silicate breaks down into calcium hydroxide and silicon dioxide. These react with each other and water to form calcium silicate hydrate.

Wet concrete is NOT acidic, all that calcium hydroxide makes it instead a strong base (pH is 12 to 13). As the concrete hydrates (hardens) the pH gradually decreases some towards neutral, but even at 28 days, 15 to 20% of the calcium hydroxide remains unreacted, leaving the concrete with a pH at 10 or more.

Concrete is at the OPPOSITE end of the pH scale from anything that can be considered an "acid".

Another thing to add for not placing wood posts in concrete. Before hiring the guy who built my shop I asked him his technique for placing and back filling the 6-inch x 12-inch posts, he uses the natural soil if adequate. If not he would truck in pee gravel. He told me when he lived in Pennsylvania he made a real good living replacing posts that were placed in concrete.

Question for you Dave, ever had a concrete burn? :o)

A statement like "concrete contains acid" just doesn't ring true to anyone that can remember a bit of high school chemistry and has handled cement powder, or remembers that cement is made from limestone. You don't have to know the specific chemical reaction of the hardening of concrete to know that a statement like "concrete has acid" CANNOT be correct.

Cement powder forms calcium hydroxide when mixed with water. Give the proximity of calcium and sodium in the periodic table, it should be no surprise that wet cement (containing calcium hydroxide) has properties similar to lye (sodium hydroxide). Both are strong bases, both are caustic, both are about as far away from being ACIDS as any substance can be.

Strong acids and a strong bases are both highly reactive substances, and either MAY have a tendency to break down wood fibers. (Though anyone that's played with such chemicals knows that organic materials do not immediately dissolve in a haze of smoke like in the movies; and there seems to be little consensus on the original issue of wood posts set in concrete).

A good engineer would try to simplify a statement so that his customer could understand the practical implications, but at the same time, generally resists saying things that are grossly inaccurate.

So I can understand a structural engineer telling you that "concrete contains caustic substances that eat wood posts", but saying that these are "acids" is carrying simplification way too far.

All that just to say you disagree with my / his wording. (Insert roll eyes icon here).

Glenn F.