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I am getting ready to build a 6' tall 80' long wooden fence, but instead of 4x4 wooden posts I am going to use metal fence posts. The fence will have 1 walk through gate and a larger gate that can be driven through. It will be attached to another fence on either side (one is sturdy, and another well is not so sturdy and I will probably replace it within a year). I think I remember reading before that I should put gravel at the bottom of the hole of each post to allow water to drain from the post.

I want to make sure the new fence I put up is done right, and that it will hold over time. So how deep should I set the metal posts, and if I should put gravel at the bottom of the hole, how much?

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2 Answers 2

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How tall are your posts to start with? A 6 foot above ground post should have at least 2 feet in the ground in your area. I would be setting them in concrete so you have a good solid base and good ballast. A metal post in concrete won't rust as long as you dome the top of the concrete so water runs away from the post.

I'll share a clever trick that works well and is very fast. After digging your hole for the post, set one or two bricks in the bottom of the hole to set your post on. You will of course have to adjust for height and plumb the post. Then simply pour an 80 pound bag of Sacrete premixed concrete mix around the post dry, right from the bag. Now just pour apx 2 gallons of water on top of the mix and leave it alone for 24 hours. You will have a solid concrete base for your posts without having to mix concrete. Mixing concrete is good, even better, but this little trick is fast and easy.

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I was thinking 8' posts, but that was part of the reason for my question. As depending on how deep it should be, would determine the length of my post. Based on your answer 8' should work pretty well. The concrete trick is a nice addition, thanks for that. –  jschoen Mar 11 '12 at 21:45
    
You can't put on too much water, plus the mix will suck moisture from the ground. If you use too much water, it just takes a lot longer to cure. Trick is to have posts on a solid base like the bricks or blocks, that is the substitute for a poured concrete mushroom. Make sure the bottom is compacted hard. –  shirlock homes Mar 13 '12 at 23:06
    
When you say "You can't put on too much water" do you mean "Be careful not to put on too much water, because you'll ruin it" or "No matter how much water you put on, it will still work"? –  Jay Bazuzi Mar 14 '12 at 1:37
    
@shirlockhomes Thanks for the tips, it worked great this past weekend, although I am sore now. Only thing I would add is to pour half the bag of concrete in, get it level and then put the rest. I found it difficult on the first post to get it to move with the hole filled. –  jschoen Mar 20 '12 at 20:35
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Good ideas listed here. I have set many metal posts for my satellite dishes in the past, and have used the dry concrete mix method, along with pre-mixing the concrete with water before pouring the sacrete. I prefer mixing the sacrete first, it cures longer (you mentioned that). Here is an idea you might want to address:

It is good to install some sort of fin to the bottom of the metal post, so it will not turn in the concrete. Turning will wear out the base fast. There are several different ways to attach fins, sometimes I use the metal brackets from the wood construction area of a hardware store, and use self-tapping sheet metal screws. Only one fin per pole is needed, from my experience.

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Please ask a separate question for the bit about attaching the 2x4s to the posts. DIY Stack Exchange is a Q&A site, so answers should address the original question. –  Niall C. Mar 7 at 12:48
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