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82 posts

Master Geek

#265517 25-Jan-2020 08:10
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I am going to be building a gate on my Driveway.
This is going to need 2 fence posts.

As it is going to be built on an existing drive, what would be the best way to secure the fence posts to concrete without the need to cut up the concrete.

The fence posts are 1800mm tall.


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1958 posts

Uber Geek


  #2406399 25-Jan-2020 08:14
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Assume you're digging a hole and putting the posts into those, filling the holes with concrete, then attaching the gate to the new posts..

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Uber Geek

  #2406400 25-Jan-2020 08:21
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How heavy are the gates? I put in a 5x5 thinking that would be good enough, I hav been told it is not good enough and will need replacing with a steel post.


You will need to cut the concrete to dig the hole, you will need to go down 900mm as a minimum, you will also want that hole to be 300mm - 400mm dia to have as good a base footing as you can possibly have.



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  #2406407 25-Jan-2020 08:40
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Because of the forces involved with a gate hanging off a post, and those forces move directionally with the gate, I wouldn't be terribly convinced there's a system strong enough to allow you to fix 1800mm posts (100x100?) to the top of your existing concrete.* However, I'm not an engineer or builder - from a layman's point-of-view, I'd imagine you'll need to dig holes and concrete the posts in.


I'd say a bit more information is needed for reliable comment from someone like @Bung, such as the type of gate you're planning to install, as well as length and height. A photo of the area would be helpful too.


How wide is your concrete drive? Could you maybe have the posts on either side of it?


* Edit: or that your concrete would be strong enough to take such forces.

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Uber Geek


  #2406457 25-Jan-2020 09:00
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What others have said.


Any bracket mounted onto the concrete with dynabolts, etc would not be strong enough to resist the force trying to tear it out.

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Ultimate Geek


  #2406466 25-Jan-2020 09:41
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I'm currently in the process of putting new gate posts in. Slightly different in that I'm digging in what was old riverbed - crowbar for every cm dug down, but at least I'm sure of the posts being solid.

That plinth is 150x250x6 RHS, 600mm in the ground with a flange welded to the top to secure the post. The hole was 900mm deep and just over 500mm wide, complete with re-bar and a power of concrete.

I haven't weighed the leaves, but they are just over 2m wide each. Even after all of the above, I'm still a little concerned that things may move over time - hence it's been two weeks and I'm still resisting the urge to mount the posts to allow the concrete to cure some more.

Unless the wooden post you are talking about using at your place is a deer fence stay with a SED of at least 175mm, I would suggest you reevaluate your plan - it's going to bend/twist/pull out, and you'll be disappointed at your wasted effort. All a bit glum I know, but do it once and do it right.

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  #2406468 25-Jan-2020 09:53
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I'd say a bit more information is needed for reliable comment from someone like @Bung, such as the type of gate you're planning to install, as well as length and height. A photo of the area would be helpful too.

I'm just an (older) amateur whose father was a carpenter. Fences at home always had long posts in deep holes but a lot of that was with hardwood. One reason to use steel posts now would be that pine seems to twist and split as it dries out so the post moves even if the base is solid. You should be able to cut the concrete and bore a hole big enough for a steel post without making the end result look too bad once it's concreted in.

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  #2406806 25-Jan-2020 17:46
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depends on the gate, if its a sliding gate you wont need too much, but any sort of swinging gate will need pretty decent post as mentioned above.

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