Installing concrete 'fence post'

[Terry Pinnell]

A section of our fence is tilting inwards. This was as a result of one of the (presumably rotten) wooden supports finally snapping at its base in a recent high wind. I reckon I can pull it back to vertical with one of those concrete posts on the outer side. I'll place it flush with the existing wooden one and secure through the bolt holes provided. I assume I'll be able to buy one from my local 'Builders Center'.

But could someone advise me on a few basics please:

1. How deep should it be buried?

1. How long should the concrete post be (and hence how far up the wooden post should its top be)?

2. I'm useless with cement; how large a hole is likely to be necessary, and how much concrete do I need to pour in? Is that ready-mixed stuff OK?

Or, suppose I get lazy or deterred when the ground turns out to be frozen solid! If I pay someone to do it, what sort of cost do you reckon, including materials?

[manatbandq]

You're going to have to dig out the concrete that the wooden post is set in so you may as well do it properly and take the whole lot out. MBQ

[Vortex]

What you want is called a "repair spur". They are about 3'6" long and the bottom 2' goes in the ground. Cost about a fiver from any old fashioned builders merchant....a bag of "post mix" and a couple of 6" coach screws.

As long as the old post wasn't concreted in too well (and with the right digging technology) you'll have it sorted in 30 minutes.

D

[Andrew Gabriel]

You can get "repair spurs" which are designed to go into the original post hole in the concrete. I've used these a number of times, and they've worked very well. You don't even need a new fence post -- I normally have to saw off the bottom where it went into the ground and the new stub then plugs into the "repair spur" socket. You can even do this without having to disassemble any of the fence if you can prop it well enough to use the saw at the bottom of the post. Then you have to lift it into the socket (you'll need some help if it's a 6' Arris rail fence with 10' spans as mine is).

The only problem is that I've never actually found the "repair spurs" for 4" posts, only 3" posts. What I have done for 4" posts is to buy a regular spike type post socket and hacksaw it shorter (you have to guess how deep you think the old post went into the concrete). Then I hammer this through the old post remains in the concrete. You must have a heavy fence post hammer for this -- forget about using 4lb cold chisel hammer or similar. Make sure the spike goes in centrally and vertically -- you get just one chance to do it right without having to dig out the concrete and start again, but so far, it's worked every time for me and the repaired sockets are all rock solid in the ground.

[Terry Pinnell]

Ah, I hadn't thought about that. Seems obvious now you mention it, i.e. that I wont just be digging into earth! Presumably 'properly' means *very* hard work, with pick-axe or whatever? (I don't have a pneumatic drill at hand!)

[Terry Pinnell]

Thanks Andrew, but (as per my similar reply to Vortex), I'm still confused about this. Is this 'repair spur' a solid concrete post of similar dimensions to existing wooden post? Or, as you seem to be implying later when you use the word 'socket', a hollow thing?

What is this 'new stub'? Assuming I've sawn off the bottom of the rotting post near the ground, and laterally pushed the post and its attached fences out of the way a few inches, I assume I'll be looking at the top of a rotten wooden 'plug' about 2' deep set in concrete?

So, this repair spur is a hollow socket? How does it fit into the existing rotten wood or concrete?

I reckon I'm going to have to visit my building supplies place to

*see* these 'spurs' and/or sockets. Must be denser this morning than usual, as I can't really get my mind around it!

[Terry Pinnell]

Thanks, Vortex, but I'm still not really clear about this. Is this 'repair spur' a solid concrete post? 3'6" long, of which about 1'6" stays above ground? If so, am I right that you're saying I do the following please:

1.Cut the post at the bottom

1. Move the fence (with 10' spans either side, heavy rose-bush running across both) laterally a few inches to clear the remaining rotten stump
2. Somehow (!) drill or clear out the rotten stump (presumably 2' of it) from its concrete base.
3. Place the new concrete post ('repair spur') into this freshly cleared hole.
4. Possibly add new cement, to make good any looseness caused by the clearing out
5. Secure new post flush to old one with bolts (9-10" surely, to pass through both posts?)

[Terry Pinnell]

After a little excavation, I've shown the situation here:

4" post is leaning inwards to the garden patio, snapped close to the surface. The concrete in which the rest is embedded looks pretty solid!

I've also done some googling and see these 'Metpost' things, which I now realise Vortex and Andrew must have been talking about. This one from B&Q will hold a 4" post.

"Metpost Fence Post Support Red 100x750mm Dimensions: (h)110 x (w)110 x (d)895 mm the wedge grip heavy duty post support is for use with 100mm timber posts ideal for heavy duty fence panels ... £7.98"

But I still don't see how I'd get that in place? Are you supposed to remove the concrete first and replace it? Surely you can't just

*hammer* that wedge in? And, even with that done somehow, what then? Is the remaining (rotting) bit of post meant to be lifted (!) into the hollow bracket? Surely that wouldn't hold up? (And the lower part of the fence would probably prevent lowering the post right in anyway.)

So, going back to my original idea of a solid new concrete post, say

4' long (equal lengths above and below the surface), what would be the best way to secure that please? How about something like that Metpost, but instead of a wedge below the 'holding compartment' it would have a robust horizontal flange, with 4 holes near each corner. I'd have to then drill appropriately positioned holes into the old concrete, and use some sort of 'self-tappers for concrete' to bolt it down.

Any further advice would be much appreciated please - before I settle on throwing money at it and getting out my Yellow pages!

[Gavin]

Having spent the weekend replacing a few panels and posts, it was hard work, but I got there in the end. I would say just go buy yourself two bags of "post cement" mix, from any of the sheds. Dig out the slab of concrete that is currently holding the fence post in place (this is the hard bit!!!). Plonk you new Conrete post in the now empty hole, go deep enough so the top of the post lines up with the fence, probably 2 ft deep. Then line the post up with the fence, and then pour in the dry cement mix around the base of the post. Fine tune the virtical hold, pour water onto the dry mix, job done :-)

Terry P> After a little excavation, I've shown the situation here:

[Terry Pinnell]

Thanks Gavin. Unfortunately, due to the patio (brick) on the other side of the fence covering some of the concrete, and the sheer weight of the fence, I fear digging out the whole slab might be impossible. Perhaps a strategically positioned stick of dynamite...?

[Rob Morley]

If it's a good solid lump of concrete why not drill/chisel the rotten stump and stick a new post in the hole?

[Terry Pinnell]

The snag with that is that I would have to remove all the fence panels on either side if it. As mentioned, they support a very large, thick rose tree, about 20' long. And I doubt I could do it without breaking the panels. I'm still hoping for a relatively simple fix!

One possibility might be to do as you say (drill/chisel out the entire remaining post - down what, about 2', so not an easy task) and then place a new concrete post (spur?) in the hole, bolting it to the existing post. But that means the fence will have to be moved inwards about 5" at that point. I've no idea whether it will move at all, but if it does I wonder if it will spoil the line of the fence?

So perhaps the best bet would be along the lines I speculated about up-thread, bolting a 'flanged holder' onto the existing concrete. Since then I've found you can get such a thing:

that raises issues like:

- could I successfully drill 4 holes into the concrete

- on such an uneven surface, would it prove impossible to get the new post vertical?

[Peter Ashby]

A spike on the bottom and a hole to place new pole in. You hammer it into remaining wood in concrete, trying to keep it square then insert new fence post and secure to spur by indicated method.

Peter

[Andrew Gabriel]

The thing I'm thinking of is effectively a double ended post socket. One end is just like the regular ones you can get on a spike or a flat plate, and the other end is another socket which you hammer into the hole left in the concrete block. It's actually slightly smaller as it's outer dimensions match the original post, and it wedges itself between the concrete and the old post wood which you don't remove. This end usually has only two or three of the four sides, and is cut into a spike shape rather than being cut off square.

As I said, I've not seen these for 4" posts though, only smaller ones.

The 'new stub' is the cleanly cut bottom of the fench post, cut to be just above ground level (so the post end sit's above the moist ground rather than in it).

Yes, with the repair socket hammered into it.

You hammer it in.

I found a good picture of what I'm talking about...

[Rob Morley]

You could remove as much of the old post as you can reach, then place a couple of pieces of angle iron in corners of the hole and fill the hole with concrete. Attach the remaining post to the angle iron with a few coach bolts.

which won't be easy from the sound of it.

Hire a chunky rotary hammer drill and you can do it.

Easy enough if you slap a bit of mortar on it to level it up. I'd do this after drilling (and plugging the holes so the mortar didn't fill them again). Or you could set studs into the concrete and mount the flange between nuts to make it adjustable.

[Terry Pinnell]

Thanks for all the advice. I decided in the end to get a 'fence man' to do it for me. He looked at my initial excavation, as per the photo I posted up thread, and quickly came to the same conclusion I'd pretty well reached myself. He'll break up and remove the concrete this side of the remaining post, and cement in a new 4" concrete spur flush with it. £40 total.