Replacing fence posts in retaining wall recess

[silly_savage]

Along the side of my property is a retaining wall dropping about 750mm to my neighbour's property. A fence stands on top of this with the 75mm posts on my half (the fence is mine on the deed plan) recessed into slots in the wall.

These posts are not secure, they may well be rotten and don't appear to be fixed into anything substantial under the gravel.

My plan is to redo the whole fence, starting with the posts, but I'm at a bit of a loss as to how best to fix them. I'd like the posts not to encroach on the path anymore than they already do to maintain space for a mini digger when we redo the garden properly. It's a relatively sheltered spot, between two houses, so I'm not hugely concerned about wind, and the prevailing wind blows from the side of the wall, so I'm not too concerned about it pushing the wall down.

My major concerns are:

Getting enough concrete around the post, considering it's recessed into the wall. I could easily end up with only 1/4 the pretty actually encased in concrete.

Water getting trapped in-between the wall and the post (which might have accelerated their demise to this point).

Having to do this jobs every again: if I ever bother to upgrade the path from the crappy concrete slabs there at the moment it'll only become harder to get another rotten post out.


To that end I'm thinking of getting the existing posts out and replacing them with these concrete-in post shoes. They are nearly as long as a post would be (2400 post/1800 fence/600 in-ground) and will allow at least an inch of concrete on each side of the post (which should bond to the wall bricks too).


Any thoughts or experience on this plan? I was originally looking at bolt-down post shoes fixed on top of the wall but after some light reading I realise that's a pretty bad idea.

Sorry for the essay. I tend to overthink these things!

 

[freddiemercurystwin]

Firstly your first three pics show posts going down to the ground then the next two show a wall with posts on the other side, perhaps some photos of the whole fence might help explain things .....

But on to your proposal, are you saying you hope to hook the rotten post ends out and then cast your steel post supports into the remaining 4x4 holes?

 

[silly_savage]

Firstly your first three pics show posts going down to the ground then the next two show a wall with posts on the other side, perhaps some photos of the whole fence might help explain things .....

But on to your proposal, are you saying you hope to hook the rotten post ends out and then cast your steel post supports into the remaining 4x4 holes?

Sorry for the confusion, the pic with the wall, that's from my neighbour's side, just to demonstrate the height of it. My path is roughly 100mm from the top of the wall.

That's about the size of it except the holes will be 3x3, or probably more like 3x5 or so by the time I've wiggled the posts out.

 

[silly_savage]

I should add that I'm strongly leaning towards some kind of hit & miss panelling to reduce wind pressure on the wall, and like I say, it's in a pretty sheltered spot anyway.

 

[silly_savage]

Sleeping on this, I'm more certain that I'll just use the Durapost steel posts. This should allow a good inch around most of the post and fully bond it to the wall if I can do it right.

Most videos I see show the post in place and then concrete/post-crete poured around it. However in the recess I have that would stop the flow of concrete around the post so I'll need to fill the hole with concrete and then poke the post in.

Will be more expensive than wooden posts but should be cheaper than all those brackets.

 

[freddiemercurystwin]

My issue would be that the fence will have no resistance to any kind of wind or horizontal forces, only being fixed at the base so a bit of a flawed idea I think despite how sheltered it might be, your brackets are designed for supporting posts that are braced elsewhere. If you can get the timber posts out with the concrete footing staying intact you might be able to shove concrete fence posts down into the holes.

 

[Deluks]

Freddie's solution is the ball-ache option, but it's probably what I would do.
Digging out a rotten post and leaving the hole intact takes a bit of patience, as the timber in the bottom of the hole is usually still sound. Drill lots of holes in it, chisel/bolster and a club hammer to split it, and then try and pull it out by grabbing the splintered ends with a pair of mole grips or pliers, I use an old pair of waterpump pliers.
It will come eventually, then you might be able to whack a metpost spike into the bottom, although the wall and its foundation which impede this.
Or drop a new post in and spoon feed postmix down the sides, and a few bits of slate.

Digging it out the 'normal' way would usually involve wiggling and leverage, you could end up damaging the brickwork and needing to partly rebuild it.

You might well find that there are metal post sockets just under the surface anyway.

What about fixing the posts back to a ledger board on the building wall, and putting a plastic roof on it? This will stop the posts from moving, and give you a dry walkway, but make sure you know the height of the mini digger first.

 

[silly_savage]

Digging it out the 'normal' way would usually involve wiggling and leverage, you could end up damaging the brickwork and needing to partly rebuild it.

Thanks for your thoughts. Maybe I'm naive, but I think they might not be too badly rotted, just possibly not secured very well (haven't found any concrete yet) in which case I'm hoping they come out relatively cleanly.

 

[Notch7]

I cant understand what is going on

the image from the side with the retaining wall shows the fence posts behind the wall

but the other side indicates they are set in the wall

 

[silly_savage]

I cant understand what is going on

the image from the side with the retaining wall shows the fence posts behind the wall

but the other side indicates they are set in the wall

Explained already, that's my neighbour's side, it's a boundary wall.

 

[Harry Bloomfield]

Thanks for your thoughts. Maybe I'm naive, but I think they might not be too badly rotted, just possibly not secured very well (haven't found any concrete yet) in which case I'm hoping they come out relatively cleanly.

Explained already, that's my neighbour's side, it's a boundary wall.

How well do you get on with them? If you think the post might pull out, if pulled vertically....

Take three scaff poles, or lengths of stout timber. Clamped or lashed into a tripod above each post, then use a hand winch to pull the posts out of the ground.

 

[silly_savage]

Well the old fence came out without a fight. No concrete, no bolts or shoes, just semi compacted sub-base. The holes are only about 350mm down so need digging down a bit, and probably enlarging cross section in the process.

I think I have a plan to dig the holes deeper (or a list of things to try anyway). Limiting factor is the 125mm over to the path. In an ideal world I don't want to disturb that as I'm sure some of the slabs would crack and it's more work.

My mind is turning to installing the new posts. I've ordered Durapost steel fence posts which are 55x54mm. The holes are anywhere from 80-115mm x about 80mm.

Given I'm aiming to get concrete all around the post I can't decide whether the best tactic is to mix a wet concrete (with small aggregate, like grano or 10mm stone, fill the hole and poke the post into it, or go for a dry mix and try and compact it around the post. The latter might be tricky, given the restricted space around the post.

 

[Harry Bloomfield]

Given I'm aiming to get concrete all around the post I can't decide whether the best tactic is to mix a wet concrete (with small aggregate, like grano or 10mm stone, fill the hole and poke the post into it, or go for a dry mix and try and compact it around the post. The latter might be tricky, given the restricted space around the post.

I would suggest....

Once you have checked the depth is enough, plus a bit - lay a bed at the bottom, to get the post to the height you need. Arrange props, then fill it around the sides.

 

[silly_savage]

That's just it, getting concrete into a 25mm gap will... Interesting.

 

[Harry Bloomfield]

That's just it, getting concrete into a 25mm gap will... Interesting.

Tamping it down into place, with a stick.