Fence posts and sewers

[Bromley86]

It's time to fix our wobbly fencing. I could just replace the panels (after repairing one of the rotted posts with one of those metpost repair spurs), but we'd like a gate in the fencing. Of course if I do that I'll need to take out the old posts and put new in in different locations.

The problem is that there are two sewers running under the fence. I have the plan that came with the title deeds showing Foul sewer (adopted) and Surface water sewer (adopted), but that's just accurate enough to tell me that they are in the area.

We were planning to dig down 750mm (exposed to strong winds) and concrete wooden posts in. What's the best way of digging the new post holes and not damaging the sewer pipes?

Should I use those concrete-in metposts, as they only go down 450mm? I'm worried that they won't be stable enough with a 5.5' feather edge fence on top because the wind hits it square on.

[Roger Mills]

How deep are the sewers? Mine are over 2 metres, so fence posts above them wouldn't be a problem. If you don't know how deep they are, you can probably find out by lifting the lid of one or more inspection chambers. That should also give you the line of the sewers.

[Andy Champ]

A spade. They're pretty tough, you'd have to be really ham fisted to break one by hand. A machine or a pickaxe would break one with no problem (as my neighbour found out...)

I'd also suspect a metpost would puncture a plastic one quite nicely, or crack a ceramic one.

Andy

[Bromley86]

Thanks guys. I hadn't thought of lifting a cover to determine depth, although that might be a bit risky as the nearest cover is some distance away in the road and the intervening ground is a variable- gradient hill.

Nice to know I should be okay with hand tools. Hopefully the ground is less impacted than on the other side of the property (clay newbuild territory). There I needed a pickaxe to get down 2', which might be the wrong tool with all those pipes around :D . I can see the worry every time I hit a stone is going to slow this one down. Maybe I'll leave the old posts in place until after I've got the new ones in, just in case.

Oh, BTW the metpost in question is actually blunt ended. You dig a

450mm cube, drop a load of cement/ballast in and fix the fitting in that. Never used them though, so I'm not sure if they're any good. Although I find metposts in general ugly, I like the idea of easy post replacement. I think I'll use the spike ones for the timber compost bins.

[Rod]

A number of years ago I used a couple (yes, just two) metposts - spiked sort. After incredible effort, using the 'proper' tool, they were just about usable. This year, I took them out and installed new posts into concrete.

The original metposts had twisted as they went in. I had done what I could to straighten them but they always were slightly off square. Seeing the state of the spike when it came out showed just how bad they were.

They had not gone in as far as I had wanted - but I could get away with that. Having now dug out the same position, the large flints explained why they would go no further.

Due to the twisthing and some degree of buckling, the metposts were more heavily rusted than I expected.

I can see their utility in a place without stones - nice deep soil. But not in most of the places I have ever lived!

As regards the concrete type. Well, they also sell bolt down ones. Seems to me that it would make more sense if the concrete ones were two part - the top being like the bolt down, the bottom having four studs. Encase the lower part in the concrete. Then screw down the top part. Main advantage? If it is not perfectly true, you could add washers to true it up. Also would allow replacement of upper part if needed.

[Bruce]

Divining could tell you where the sewers are, and help you avoid them. Your local water company responsible for drainage in your area should be able to help. They might even locate them for you, probably free of charge, in order to avoid any disruption to their pipes.

Alternatively, try a divining course yourself. There are courses all over the UK:

am very sceptical by nature and thought divining was a load of bull until someone taught me how to do it. After about half an hour I could locate all kinds of underground services. I could not believe how easy it was, and so far, it also seems to be quite reliable.

[Roger Mills]

That's *not* how they think! When I built my new garage over sewers, I had to have a CCTV survey done at *my* expense before being given provisional permission by Severn Trent - then another one after the event, to prove that no damage had been done, before they would ratify the permission.

[Roger Mills]

If your old posts were concreted in, but have rotted - leaving concrete sockets - I'm pretty sure you can get Metposts designed to go into the holes in the concrete. That should avoid any danger of causing damage to sewers.

[Martin Bonner]

Ah, but with a garage they have the option to deny permission so they can pass the cost to you. With a fence they don't have that option (although they may still say - "you break it, you pay to fix it").

[Bruce]

Roger has made a good point. It depends very much on the water company. Some are very helpful, others are extremely unhelpful.

[The Medway Handyman]

Go to Wickes & invest £30 ish in;

Post Hole Digger

demolitian crowbar. post hole digger is amazing, clean round hole 2' deep easy peasy. Crowbar breaks up the earth & stones & can be used to remove half house bricks etc.

Funny enough I used two of those today for the first time, not on a fence, but to hold 3 x 3 posts that support part of a deck. They seem very good, but not sure I'd use them in a high wind area.

[The Medway Handyman]

Called a metal repair spike

in 3" & 4", but the 4" are a bugger to get hold of.

[Bromley86]

Thanks - I'll be using one of these on another (low wind) area of fencing where one of the posts has rotted though but the rest are solid.

Can't use them on the section I've been talking about as I'm having to reposition the posts (even the intact ones) because I want the new gate in the "right" place.

Thanks to everyone else for the tool and water co. advice.