Gateposts for heavy iron gates

[CliffordPope]

I have bought a pair of ornamental drive gates, spanning an opening of about 10 feet. Each gate is about 5 feet wide, and around 8 feet high, weighing 180 Kg.

There are no gateposts at present, and I want to build, or have built, a pair of nice solid pillars in reclaimed brick. Each gate will sit on a ball-bearing support at the bottom, bolted at ground level to a projecting part of the concrete footings. There is a strap hinge at about 6 foot off the ground, with a V-shaped bracket to be cemented into the pillar at the appropriate level as construction progresses.

My questions are:

What volume/size of foundations will I need? I presume the easiest is to dig a large hole and fill it with concrete to ground level, and then build the brickwork on that base?

What width of pillar should I specify? Two brick-lengths looks very slender, 2.5 or even 3 bricks looks chunkier. How can I calculate what weight a pillar of given dimensions will support, hanging at that height?

Any advice or experience would be much appreciated. Probably I will just hand the job to a builder, but I'd like to know in advance what sort of principles and dimensions are involved.

 

[Penners]

Calculating the required size of pillar sounds an almost impossible task. So much will depend on the weight of the gates, their turning moment, the weight of the bricks used for the pillars, the strength of the mortar... and so on.

If you're going to give the job to a builder, provided he's worth his salt he should be able to squint at the gates, scratch his head, drink a cup of tea and munch a Kit-Kat, then tell you what specification of pillar you need, relying purely on his experience.

Otherwise, the formula I would use is x = e x 1.5, where x is the specification of the pillar and e is your own estimate of "that's about right". In other words, make it half as big again as your best guess.

 

[Owain]

Pour the foundation and pillar as one in reinforced concrete, remove the shuttering, and clad the pillar with brick. Attach the brackets by bolting through the brick and right through the concrete.

 

[vicky whitworth]

Are you sure that's what you want to do? What about the pain in the butt of getting out of the car, opening the gates, getting in the car, driving through, getting out of the car, closing the gates, getting in the car, drive the rest of the way up to the house? And please, please don't have that arrangement where the gates automatically swing open like you were a coffin at the crematorium. Down these parts we have a word for those people and it's not repeatable here
Perhaps you plan just to leave them open and grand looking. That's what I'd do.

 

[Flyfisher]

Pour the foundation and pillar as one in reinforced concrete, remove the shuttering, and clad the pillar with brick. Attach the brackets by bolting through the brick and right through the concrete.

Probably a good idea. The stress of a 5-foot 180kg gate on the hinges in a brick pillar should not be underestimated. I've seen loads of leaning/crumbling brick pillars that were unable to cope with the stress of heavy gates. Brickwork is only strong in compression but relatively weak in tension and a heavy gate on embedded hinge pins is akin to using a big cold chisel to break apart brickwork - a surprisingly easy task.

A near neighbour where we previously lived solved the problem by using a very heavy RSJ set very deeply into a large concrete base (3-4 feet deep I would guess). He then had the hinge pins welded to the RSJ, complete with triangular supporting steel piece. The whole thing was then clad in brickwork but the stresses from the gates were never actually transferred to the brickwork itself.

Same basic idea as Owain's suggestion really - try to keep the brickwork ornamental and not structural.

 

[LadyArowana]

A near neighbour where we previously lived solved the problem by using a very heavy RSJ set very deeply into a large concrete base (3-4 feet deep I would guess). He then had the hinge pins welded to the RSJ, complete with triangular supporting steel piece. The whole thing was then clad in brickwork but the stresses from the gates were never actually transferred to the brickwork itself.

Same basic idea as Owain's suggestion really - try to keep the brickwork ornamental and not structural.

Big bits of metal and concrete must be surprisingly strong. A new condo is currently being built opposite us that will have several "lap pools" projecting 14 metres out from the tower. I presume they have calculated that even filled with water they are not going to snap off....... well one would hope. Personally I would need to be persuaded into such a thing at gunpoint.

 

[agbagb]

Instead of casting your own reinforced pillar, a concrete fencepost or a lintel set in the foundation might do the trick.

 

[CliffordPope]

Thanks for the suggestions.
I have been advised elsewhere that un-reinforced brickwork is surprising weak, and that a steel post set in concrete is the way to go.
I have also been told that it is highly desirable to cast a continuous concrete foundation across the drive linking the two pillars, because otherwise a tiny relative movement can put the gates out of alignment.

I take the point about the fag of opening and shutting the gates, but that's unavoidable. Cows often wander up the road, and a moment's carelessness in leaving the gates open has a herd in the garden.

 

[LadyArowana]

I take the point about the fag of opening and shutting the gates, but that's unavoidable. Cows often wander up the road, and a moment's carelessness in leaving the gates open has a herd in the garden.

Well that's steak for supper sorted then.

 

[Penners]

I take the point about the fag of opening and shutting the gates, but that's unavoidable. Cows often wander up the road, and a moment's carelessness in leaving the gates open has a herd in the garden.

Of course, you could splash out on a whizzy electric gate opening system. Press the button on your remote control and the gates glide open, then close automatically once you've driven through. No sweat and no herds of bison in the garden. You can even fit an intercom system so that Great Aunt Matilda can press a button on the gatepost and talk to you in the house. You can then decide whether to admit her or not (depending on whether or not you want to be in the Will).

Ain't science amazing?

 

[LadyArowana]

I take the point about the fag of opening and shutting the gates, but that's unavoidable. Cows often wander up the road, and a moment's carelessness in leaving the gates open has a herd in the garden.

Of course, you could splash out on a whizzy electric gate opening system. Press the button on your remote control and the gates glide open, then close automatically once you've driven through. No sweat and no herds of bison in the garden. You can even fit an intercom system so that Great Aunt Matilda can press a button on the gatepost and talk to you in the house. You can then decide whether to admit her or not (depending on whether or not you want to be in the Will).

Ain't science amazing?

Get the CCTV too, then you can see that it's Great Aunt M, ignore the buzzer and still be in the will.

 

[Penners]

You need to read more P. G. Wodehouse, Yer Ladyship. Visiting Great Aunts are not so easily deterred.

 

[Keith Bowman]

I want to know Vicky Whitworth's word for the self openers! Perhaps, given the coffin-at-a-crematorium analogy, it is simply 'corpses'?

 

[DJH]

gate piers don't have to take the weight of the gates but merely act as pivots for them to hinge open. Ideally the hanging end of the gate pivots on the ground via a plate or metal socket that the end of the hinge sits in and the function of the ring irons built into the pier is to hold the gate upright and not to take any weight. Another alternative is to have a wheel on the opening end of each gate tracking on steel plates or the drive itself if the surface is sturdy and compact enough. There's no need for non-period concrete, steel, welding etc...

Doug

 

[Flyfisher]

I have been advised elsewhere that un-reinforced brickwork is surprising weak, and that a steel post set in concrete is the way to go.

You mean you didn't believe the collective wisdom of PPUKers? :shock:

I take the point about the fag of opening and shutting the gates, but that's unavoidable. Cows often wander up the road, and a moment's carelessness in leaving the gates open has a herd in the garden.

Cattle grid?

 

[Moo]

Cattle grid?

But then you couldn't have that clever wheel system - or could you?

 

[Flyfisher]

I was thinking that gates might not actually be necessary at all, if the main reason for them was to keep out cattle.

It was a little tongue-in-cheek though.

 

[LadyArowana]

Cattle grid?

:lol: :lol: :lol:

 

[Zebra]

herds of bison in the garden

Sounds like my kind of party.

 

[CliffordPope]

Thinking about this more:

1) Yes, I know the pillar doesn't literally take the weight of the gate, but the sideways force on the top hinge is enormous.
I did a calculation of moments, imagining the pillar merely resting on the foundation, and pivotting about the lower bearing point. I calculated the weight of 3 sizes of pillar - 2, 2.5 and 3 -brick square section. With only 2 bricks, pillar was only just heavy enough to stop the gate from pulling it over over. 2.5 bricks has twice the moment of the gate, and 3 bricks 3 times.
( A wider pillar is not just heavier, but has its centre of gravity further from the pivot)

So in theory a 2.5 brick pillar should do easily, as long as it holds together and the top hinge doesn't pull out. I think the idea with a metal reinforcing post is also to weld the top hinge to it.

2) I did think about a cattle grid, but that would need room for both a grid and a gate so that we could get horses past.

3) Apparently both the bottom bearing and the top hinge strap incorporate some adjustment, so perhaps any small movements could be accommodated.

4) Another thought is that if the gates had wedge-shaped metal rests in the centre and in their open positions, then they would not normally be hanging on the pillars at all. So perhaps the notion that they would be slowly sinking towards each other from years of steady pressure can be discounted.