Found hole in garden

[PearlHeart3]

Hi all, posting here in traffic as I posted something over in the garden section that never had a response.

We are in the process of ripping up decking in our garden that was laid by previous owners approximately 8 years ago. We discovered a hole straddling the boundary separating our garden with the neighbour's. At first we thought it might have been an old sewage pipe and the hole an access point, but I've shoved a torch down there and took some photos. There appears to be an armoured cable in there which is coming out/in to my neighbours side.

The hole is approx. half a metre wide but underneath it goes back further in a round shape and is approx. 2 metres wide. The next door neighbour appears to have put concrete over the top on their side and lots of gravel. I've attached some photos of the area to give you an idea of scale. It's really hard to describe!

Does anyone know what it might be? Or who I should contact about getting it checked out? Would a surveyor know? Feel free to ask more questions!

@PigletJohn - Thank you for popping into my thread and having a look and read through.

You're right in your second post with regard to the placement of the soil pipes on both mine and my neighbours house. I've uploaded the plan again, although this time I've added a yellow circle which shows where a manhole cover is in my alleyway. You're right that it carries the waste from my house. The neighbour opposite also has his waste pipe in the mirrored position. Our waste would also pass through the hole I uncovered today, although would the pipe be further underneath the hole? I can't see any real pipework down there apart from that cable (there's lots of old bricks and rubble down there).

The neighbour might also have a mirrored manhole cover in their garden but they have gravel over the top of their concrete so floor so I can't tell.

I guess my questions are: Is the hole problematic? Should I do anything with the hole? I'd like to lay a patio over the top (the current decking was laid over the damp proof course level) but I'm not sure how much further I could dig down if underneath has drainage. Should I just cover over the hole with a thin layer of concrete, or manhole cover? Granted, I don't have access to the entire hole as 3/4 of it is in the neighbour's garden buried under their concrete path.

Sorry for all the questions!

@SynchroSwimmer This might be an option! Thank you.

@PigletJohn Updated plan attached.

I think you need to get a builder in to dig it up. It is not complicated work.

If there is a shared portion, you can ask the water company to repair that.

If your neighbour has a separate pipe that is also leaking, and they are insane and refuse to have it repaired, the builder can put a brick wall in your hole to prevent their water coming through the boundary. It might last 20 years or so. Or you might have some legal recourse.

The hole will carry on getting bigger and bigger until it is fixed. If you cover it, the cover will fall in. If you fill it, the filling will fall in. Eventually your house will fall in.

These cavities caused by leaking drains are very common. I expect yours has been covered up, filled in, and the concrete patched several times. The decking might have been an attempt to hide it. You can have a drain surveyor poke a camera down from the manhole, but digging is the only answer. It has probably been broken since 1942.

Choose the firms by local recommendation, not by internet search. Don't ring an 0800 or 0300 number, which will be an agent.

We have an armoured cable going to the shed from the house, but we pinned it along the fence, didn’t fancy digging up concrete to have it underground. You can buy a voltage tester to check to see if it’s electric (I think, we have one, not sure what it does)

Just to be clear, when I said "of course it is a drain"

I meant a broken, leaking drain. It is not a soakaway or a dumb well.

It is broken and leaking sewage and water into the ground next to your house, washing away the soil and leaving a cavity, and it will not get better, it will get worse.

This is a very satisfying thread.

I was just thinking OP needs pigletjohn and there he is with an answer.

You're brilliant Piglet

You need something like this
www.ebay.co.uk/itm/283888419904

Piglet 👍

@PigletJohn If it was leaking, wouldn't I smell waste? I can't smell anything down there. The hole is domed shaped inside which indicates (to me at least) that the hole was intentional rather than caused by erosion.

Would you mind pointing out where you can see the lead pipe? I will take another look down there tomorrow when it's daylight and try and get my proper camera down there which has a bigger flash. My phone camera doesn't really show the detail of the domed walls.

I've attached some other photos I took of it earlier today.

Photo 1: I put my hand in the hole and had my camera pointing upwards to take an upshot of the neighbours side of the hole. You can see the bricked border around the perimeter of the hole and their concrete patio on top.

Photo 2: I've labelled some bits in there. The part I've marked "Domed wall of hole" isn't that clear in this photo because the flash on my phone didn't light it up enough, but it looks to be made of brick. Unless this is the inside of the lead pipe you mentioned? I hope it's a bit clearer.

Full size image links if you need them.

Photo 1: www.mumsnet.com/uploads/talk/202006/large-616716-hole1.jpg

Photo 2: www.mumsnet.com/uploads/talk/202006/large-215573-hole2.jpg

I think it's a Victorian water cistern. I've got one - that I decked over. It scares the hell out of me because it's bell shaped underground and if you (kids/dog) fell in there's no way out. It didn't come up on any of the searches and our seller didn't mention it. I hate it.

www.lrukforums.com/threads/victorian-water-cistern.226342/

Tony

I honestly don't think that makes sense. It isn't a brick lined chamber. It's in a built up area. It's positioned on the line of an old drain. It's a cavity that has been filled, patched and got worse. It's caused collapse of the surface above. It isn't very deep. It's damp but not full of water. How would anyone consciously build two houses astride it?

PigletJohn I would take your opinion over mine any day, you know everything.

I only commented because I have one and it does straddle two gardens. It takes all the rain water from the gutters from a row of houses. There's a lead pipe, similar to OP mentioning, which connects (did until I took it out) a cast iron pump. It's ingenious and bloody dangerous all in one go.

I see the brickwork now and find it very surprising.

The shiny grey/black thing in www.mumsnet.com/uploads/talk/202006/large-764391-20200603-162842.jpg
looks to me like lead pipe.

@PigletJohn Ah, yes I can see that looks like a lead pipe. I assumed it was some sort of armoured cable for electricity or something. Thank you for your advice and comments. I have just fired off an email to the really good (local) RICS chartered surveyor who did my survey when I was in the process of buying the house a few years ago. I sent through some photos (I should have sent him a link to this thread to be honest but I need to keep it professional!). I've asked for his help (paid) or if he could put me in touch with someone who can have a look at it.

I'll keep you all updated once I learn more.

@TonytheDog I had a look at the thread you posted - I can see why you might think it's the same. It's terrifying me too. I sort of wish I never bothered trying to lay a patio.

@19lottie82 I do but I'm hoping I can just pay someone to come out who already has one. I don't think I could find much use for it after this little project.

Thank you to everyone else who has commented so far.

How old are the houses? I used to own a Victorian terrace and my mains water pipe ran across my neighbours hallway before coming into my house!!! Only showed up when there was a leak. So to fix my leak I had to dig up their hallway. Older houses I have bought have had water supplies in random places and sewerage shoved in anywhere, thousands of pounds I’ve paid out to sort out these houses.

@ladybird69 My house is an Edwardian house (1906) although personally I think it's Victorian in its design. It still retains its original structure and the shared drain is shown on the title deeds. However it doesn't surprise me of the situation you described. There are positives and negatives to owning an older property for sure.

What did your neighbours say?

I have nothing to add except to say this is a first class post OP. Plans, photos, arrows pointing things out, a frog, an arrow pointing to a frog. Top marks!
I hope this is resolved quickly and is inexpensive.

@PearlHeart3 I’ve owned property dating from 1816-1979. The above property was in a row of terraces so it was a bit of a shock, 2 foot To the left into the front garden would have cleared the houses and kept everything separate but never knew what was going on in bui,ders minds!!!!. Luckily I was used to the surprising things renovating houses could through up so always made sure that I had good insurance cover. The 1816 house was amazing, it has original windows that were gradually giving into gravity and pooling at the bottom of the window panes.

@ladybird69

Off topic, but the story about glass flowing over time is popular, but not right.

In the days of spun or cast glass, it was not perfectly flat, and glaziers were trained to fit it with the heavy (thickest) edge downward.

Do come back with feedback. I know for mine shafts (and maybe disused wells) it was common to fill them with pea gravel and bung a bit of concrete on top, which can then subside over the years. You would need to know a bit about the local history and geology to assess whether that was a possibility.

Just a little update.

I had a look out of my bathroom window today and noticed the next door neighbours kitchen waste pipe goes into a drain right where the hole is. I think @PigletJohn was right about it being a lead pipe which initially thought was an armoured cable. The lead pipe would be coming off of that drain, hence why it comes in from the ground (the ceiling of the dome if you will). The pipe carries on down into the ground, further into the big hole, so maybe it connects to a larger sewer pipe not visible?

Maybe the hole entrance (the small circle you can partially see on my side that has a perimeter of bricks was an access hole to service the lead pipes at some point? I'm assuming I have the same setup from the other side but I can't see it because of the angle and the fence. Just a thought.

Oops, meant to attach my photo.

The neighbour's brickwork and other details look fairly modern. The gravel probably hides broken concrete. The bottom courses of bricks are dark, suggesting damp, probably associated with the adjacent gully and downpipes.

@PigletJohn good spot. Just out of shot of the photo where the gravel is, they had a leak coming from an overflow pipe (I think) which was coming out of their top floor bathroom wall. It dripped constantly and for a good year that I moved in. It left the brick wall all damp. They finally got it fixed but I think it must have been dripping for a good few years before I moved in. I agree the gravel must be hiding broken concrete.