screwing a gate post into concrete

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hattrick123

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#204772 17-Oct-2016 11:09

hi there

I am looking at screwing a gate post into concrete. Can you advise what my options are? As I am not sure what is the best
method to handle the weight of the gate.

The post is about 4ft tall.
The gate is about 12ft long and rather heavy.(can barely lift it up a bit on my own but need 2 people to move it)

my research so far is that I should:
1 - use a bolt anchor (drill a hole, bang the bolt in and then tighten)
like this https://www.bunnings.co.nz/ramset-trubolt-stud-anchor-m12-x-180mm-galvanised_p00459549
or here https://www.youtube.com/watch?v=BKCHs-ycQ6U
2 - use some epoxy (drill a hole, pour in the epoxy, add the bolt, let it set, then tighten)
like this https://www.youtube.com/watch?v=q2iKgMKmFiM

3- Since I will be pouring the concrete to create a pad for the post to anchor to I was wondering if I could
place some sleaves in with the concrete and then when set just position the post and screw bolts in.
maybe something like this https://www.bunnings.co.nz/ramset-dynaset-drop-in-anchor-flanged-m10_p00886261

Can you advise?

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#1652184 17-Oct-2016 11:14

I suggest the concrete will be under a lot of stress, and will crack. What about a wheel under the end of the gate?

richms

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#1652195 17-Oct-2016 11:26

Can you not just stick the pole in the ground before you pour the concrete? Does it have to be removable?

This is something that will be under a crapload of stress, so probably worth consulting with an engineer that does this for a living.

Richard rich.ms

hattrick123

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#1652197 17-Oct-2016 11:28

tks, Have no problem putting on a wheel, as it will probs makes sense, although that is something else I will have to work out. just trying to work out the best way to attach the post to the concrete first.

MikeAqua

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#1652198 17-Oct-2016 11:29

The conventional approach for timber posts is to use a post one third longer than the height of the gate and dig it in.

For example for a 4 foot high gate get a 6 foot post, dig a hole 2 feet deep, position post and pour concrete into hole.

You can also bolt the post onto reinforced concrete. As a 12 foot long heavy gate will exert a lot of force on the post, I suggest you will need to go fairly heavy duty to make something that lasts.

Its hard to know what is appropriate to suggest without knowing what sort of gate it is, what sort of post and what surface it will swing across.

Mike

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#1652208 17-Oct-2016 11:37

Bang on suggestions from the first two answers.

I'm not a builder or an engineer but from your description of the gates weight and length (but not height or material) my first thoughts were that the post you have and the methodology you're thinking of will be woefully inadequate. Although the use a wheel as tdgeek suggests would be a great offset.

What are the actual dimensions of the gate, what is it constructed of and how much does it actually weigh? - there are engineers and builders that come to this site so this sort of information will be useful if they feel inclined to comment.

hattrick123

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#1652220 17-Oct-2016 11:53

Its a steel gate, with a piece of steel(20mm long) with a hole in it as the hinge(2 hinges). these 2 hinges with the holes sit on 2 divits(not sure what they are called), on the post to create the swing. The post is steel also and is slightly taller than the gate. But it looks like the post is just meant to attach to the concrete as it has a plate at the bottom to put 4 screws/bolts through. So without doing some extra work I can't put the post in deeper. I would have to attach the post to something else to achieve that deepness.

There is another hole at the top of the post that is used for attaching to a wall or other post that would greatly strenten the post.

I will try and post some pictures(edit: and dimensions) later.

The wheel might not be an option as I want the bottom of the gate to be close to the groud as it has to keep a small dog in. Still achievable, but I might have to attach the wheel on to the side of the gate as opposed to attaching it under the gate(taking more wight).

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#1652240 17-Oct-2016 12:17

Steel post. It is designed for bolting down. Did you buy this new? It would normally come with a specification sheet detailing the size/length of bolts required and any bracing required.

MikeAqua

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#1652284 17-Oct-2016 12:34

OK so you are correct you need to make a concrete pad and bolt the post to it.

I would make the concrete pad about twice the size of the steel plate and go at least a foot deep. Make the hole wider at the bottom.

You need to reinforce the concrete near the surface with some light mesh (that you can drill through it if you have too).

You will drill dyna-bolts (one for each hole in the plate) into the finished concrete pad and you want the mesh to end up roughly 1/2 way down your dyna bolts. The diameter of those holes will limit your choice of dyna bolt and I would go as long as you can in that diameter.

When the concrete has cured (a few days) use a hammer drill to drill holes for the dyna bolts. Drill in short burst to avoid overheating the drill tip Tap the dyna bolts in with a block of wood (avoids damaging the thread). When fully seated tighten

Supporting the gate - most of the time the gate will be closed. So you can just make a support for the outer end for the gate to rest on when closed. When I used to hang deer gates, I would drive a sharpened length of post into the ground. The outer end of the gate used to have to be lifted an inch or so to sit on it when closed. Stopped the gate sinking on it's hinges. You may want something more sophisticated but you hopefully get the idea.

Mike

tdgeek

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#1652286 17-Oct-2016 12:38

MikeAqua:

OK so you are correct you need to make a concrete pad and bolt the post to it.

I would make the concrete pad about twice the size of the steel plate and go at least a foot deep. Make the hole wider at the bottom.

You need to reinforce the concrete near the surface with some light mesh (that you can drill through it if you have too).

You will drill dyna-bolts (one for each hole in the plate) into the finished concrete pad and you want the mesh to end up roughly 1/2 way down your dyna bolts. The diameter of those holes will limit your choice of dyna bolt and I would go as long as you can in that diameter.

When the concrete has cured (a few days) use a hammer drill to drill holes for the dyna bolts. Drill in short burst to avoid overheating the drill tip Tap the dyna bolts in with a block of wood (avoids damaging the thread). When fully seated tighten

Supporting the gate - most of the time the gate will be closed. So you can just make a support for the outer end for the gate to rest on when closed. When I used to hang deer gates, I would drive a sharpened length of post into the ground. The outer end of the gate used to have to be lifted an inch or so to sit on it when closed. Stopped the gate sinking on it's hinges. You may want something more sophisticated but you hopefully get the idea.

Great idea.

Bung

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#1652314 17-Oct-2016 13:15

Unless the top of the post is braced by a wall a puny amount of concrete won't stop it just tilting. If the concrete was part of a drive it might be OK but a 12ft gate is a big lever. The next problem will be if the gate is low to the ground when closed will it still be clear while swinging open.

MikeAqua

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#1652318 17-Oct-2016 13:28

Bung:

Unless the top of the post is braced by a wall a puny amount of concrete won't stop it just tilting. If the concrete was part of a drive it might be OK but a 12ft gate is a big lever. The next problem will be if the gate is low to the ground when closed will it still be clear while swinging open.

A flared hole of a decent size filled with cement will hold quite a lot.

I hate describing these things quantitatively as I do them by intuition. My gut feel is that this a job for bag of cement with some added builders mix.

If in doubt - more concrete!

Mike

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MikeAqua

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#1652319 17-Oct-2016 13:31

tdgeek:

MikeAqua:

The outer end of the gate used to have to be lifted an inch or so to sit on it when closed. Stopped the gate sinking on it's hinges.

Great idea.

An old guy taught me that trick. Every gate on his deer farm was perfectly hung. You can make a support for the open position too, if the gate will spend much time.open.

Mike

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#1652341 17-Oct-2016 13:59

This page http://www.barriersdirect.co.uk/barriers-c1157/security-gates-turnstiles-and-railings-c1077/manual-swing-gate-p1625 describes the requirements for a simple car park swing barrier, note the size of the concrete block for the hinge post. 600mm x 600mm x 500mm would take about 10 40kg bags of ready mix.

"Main foundation 600 x 600 x 500mm deep minimum. Catch post foundation 300mm cube.

Main post required 4 qty 16mm bolts. End catch post requires 4 qty 12mm bolts."

frankv

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#1652342 17-Oct-2016 14:00

Maybe you can set bolts into the concrete (with the threads facing up :) ) to match the plate on the bottom of your gatepost? A lot easier than drilling out the concrete to put Dynabolts in. You could even have some kind of structure (e.g. a steel plate or rods connecting the bolts) underneath the concrete to spread the stress.

Beware that hanging gates right is a bit of a 3D geometry challenge. The post needs to be normal to the plane of the ground (and in the positive Z direction ;) ). Even a couple of degrees out of true on your gatepost in either plane and the end of the gate will rise and fall markedly as it swings. Worst case, it could be so high when closed that the dog can get under it, but hit the ground before it's fully open. So check that the ground *is* level... if there's a slope (again even a couple of degrees, which you might not even notice) and the gate *is* level, then you run into the same issues. Also, if you're out of plumb, a wheel at the end of the gate is no use to support it.

neb

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#1652368 17-Oct-2016 14:43

Normally I'd use a dynabolt to attach something to a concrete surface, but as others have already suggested for something like this you need to dig it in and concrete it into place.

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