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OT - digging holes
JeffHs - 20/1/09 at 07:44 PM

Guys - totally OT but has anyone any ideas?

I have to replace a deep sewer (1.3 metres from the house and 2 metres down) next to my house before I'm allowed to build an extension. I won't do it myself but I'm trying to do as much prep as possible to keep the cost down. I'm worried about undermining my house with such a deep trench so close to the house, so need to determine the depth of the existing footings of my house.
I'm looking for a way of digging small holes at intervals along the wall.

i've already dug a 1.5 metre deep trench in the lawn in a failed attempt to find the drain and the hole I ended up with was huge, so I don't want to attack it with a garden spade again

Is there any way I can drill down (tight to a wall) enough to find the bottom of the footings and to exactly locate the drain?

adam1985 - 20/1/09 at 07:49 PM

have you tried the thing with to welding rods to try and find the pipe ive never done it but have heard it works

rachaeljf - 20/1/09 at 07:54 PM

was it built before or after the sewer?

I'm a structural engineer. Might be able to help if you can answer the above.

Cheers R

blakep82 - 20/1/09 at 08:00 PM

ask the council where it runs? they should have plans.
otherwise, what about this, if you know roughly where it runs, can you digs holes well away from the wall, along the path of the sewer to find it?

great explaination of what i mean, that

theconrodkid - 20/1/09 at 08:04 PM

i used "double shovels" and a long chop spade,you can easily get down to the bottom of foundations with them and the hole can be 2 feet square.ive used divining rods and yes they do work....if there is water in the pipe,stainless seems to work best

[Edited on 20/1/09 by theconrodkid]

londonsean69 - 20/1/09 at 10:44 PM

quote:
Originally posted by blakep82
ask the council where it runs? they should have plans.


HAHAHAHA - we got some plans from Tower Hamlets and they had a 48" (yes, 4 foot) gas main missing off their drawings.



Trenching shovel, very narrow blade, used for installing cables etc.

Please be careful if digging big holes, especially if they have steep walls, they have a nasty habit of collapsing. You need to shore them up if you get much below a metre, even less if it's crap soil.

1.3m deep, 2m from house will definitely need support.

Thats well within the area that I would consider under load, as such there should be some props or underpinning while they excavate down to the trench.

Just because a drawing say it is 2m from house doesn't mean it is!!

You could always try an auger, the type you install fance posts with.

Failing that, get a frim in to locate it for you, then do the dig yourself, but please bear in mind the possibility of part of your house collapsing if it's not supported properly.
The least intrusive way of locating it, including depth, size and, usually, materil - is with a Ground Radar Survey - which is exactly what it says on the tin. Ground penetrating radar.

I work in Civil engineering and have seen various things fall over because they weren't support correctly (the most impressive was a 181 Ton 400kV transformer that just slid off it's temporary foundation, then tryed to roll down a hill - that was f*cking scary!!)

Sean

[Edited on 20/1/09 by londonsean69]

NigeEss - 20/1/09 at 10:48 PM

You want one of these

mangogrooveworkshop - 21/1/09 at 12:19 AM

What you really need is a SONDE and a cat detection system.
Put the sonde on the snake and push it down the drain/duct whilst using the cat detector to follow the route it takes.
Then you can dig. Use the cat and genny on the gas as well as the water and mark all your services with spray marker directly on the ground.
I would never just dig with augers unless you have a clear site.
Plastic gas mains and water pipes are a real pain. Fibre optic cables have a habit of having a non metallic (kevlar) reinforcing member so they make the normal detection systems next to useless.

You can rent these from the bigger speedy or hss shops

good luck and happy digginglinky thing

[Edited on 21-1-09 by mangogrooveworkshop]

Michael - 21/1/09 at 10:00 PM

How about running a string from your man hole cover to the neghbours? Then it would show the route over ground.