Breaking Concrete - What Depth for Services?

[AlexW]

I am breaking up the 4" patio in front of our house this week.

Gas and Water come in under the gateway the and into the house at the front and side of a lean to under the slab.

The Gas was put in after the main slab and been made good with a patch concrete. This was probably over 20years ago by the looks of things (pos. when external gas box was added to the house - way before our time).

Thus I would imagine would put the gas pipe at a depth which won't be affected by the breaking activity?

The mains water stop in the road is relatively modern as it was replaced a 3 years back when we bought. IIRC the depth was at least a foot (probably more like 18").

So I guess that end is OK too?

The water comes into the side of the lean to, its a copper feed up through the floor and the lean to is over well 100years old, although the pipework looks newer.

The other end of the water feed comes in next to a recessed gully at the the bottom of the slab, I can see that the slab at that point is 4" thick, so it looks like the slab may have been put in after the fact (the gully being closer to the level of whatever was there before).

My concern here is that the water feed in to the house is close to the slab and vulnerable to breaking damage or worse still embedded in the slab (unlikely I guess)?

Has anyone got a view as to whether I am just being paranoid about this or advice as to approach the breaking carefully to avoid disaster?

Once again, TIA,

Alex.

[Owain]

I wouldn't take that for granted.

Water is probably the deepest, to prevent freezing. Electricity is often very shallow.

You are not being paranoid. Chopping the gas pipe could mean the whole street gets evacuated (and I don't know how much Transco would charge you for repairing it); people have been killed or seriously injured chopping into electricity mains, and chopping the water main could make a very big mess.

You can probably turn the water off at the pavement stopcock. You may need a thingee to turn the stopcock off with though.

All the utilities have specialised departments for underground plant and (should) have detailed plans showing the exact(ish) location of services. Hopefully that extends to private land. They may come out and mark the location for free.

For Scotland,

Transco (Plant Location)

95 Kilburnie Street Tradeston Glasgow G5 8JD Tel [phone] office hours.

Moleseye (Scotland) Ltd

0800 800 333

Moleseye will notify all utilities, pipeline operators and the relevant local authority of your proposed works. Given sufficient notice then can supply you with drawings and enable you to comply with the New Roads And Street Woks Act 1991 (HAUC Code of Practice for the co-ordination of streetworks and works for road purposes and related matters) and the Health and Safety Executive document HS(G)47 Avoiding Danger From Underground Services.

You can also hire a CAT (cable avoidance tool) although whether it will work through (possibly reinforced) concrete I don't know.

Owain

[AlexW]

Owain, thanks for the info.

I know within about a foot or so where all the services are in the area, I can even dig down under the flower bed to establish the depth of the gas pipe. Electricity is overhead. Water can be turned off.

I doubt the utility co info is going to be more accurate. Especially that the data will probably been captured (possibly correct?) many years ago and digitised since.

Is this /really/ applicable and necessary for removing 4 inches of concrete from my own front garden?

Is there a better way to lift the concrete than breaking?

How deep is safe for a light duty breaker on the Gas front? I am not planning to dig anything deeper than 4" (perhaps other than an exploratory hole for Gas).

Alex.

[Owain]

No, but it is necessary if you want to sell Chinese food door-to-door on recently-completed housing schemes :-) The text was copied-and-pasted from a previous on this subject.

Lift one corner and hit it (with a jack?)? It will snap?

If you're sure the concrete is 4" then you are *probably* safe breaking to 4" but I'm not going to guarantee it :-)

Owain

[AlexW]

What happened to the r ;-) I wonder?

Cheers for the advice, i doubt it will snap easily, its uniformly 4" (I have samples from elswhere) and quite "good", builders doing the conservatory had a mare with a getting out another peice of the same slab (so they said) ... this was away from the services though.

Luckily on one end (gas meter) the peice of infill mentioned gives away the location and direction on the gas pipe within a foot or so. The infilled bit will probably lift out with a bit of perssuasion.

On the other end, I may be able to score the crete to say 1" and then use the breaker to break out sections from the edge around the which is not obviously infilled (although i might give that a scrub down to see if thats infilled too).

I'll check the depth of the gas before breaking commences. I suppose if too close to the crete then I'll have to dice the crete with a stihl saw or something less disturbing, although I am not looking forward to that....

Cheers,

Alex.

[Autolycus]

If the gas pipe was installed with a "mole", its depth could be all over the place, particularly if the ground had previously been made up with rough hardcore. The first place my hired JCB hit the pipe it was less than 200mm below the surface, but in other places it was well over 600mm deep. If the gas pipe is yellow plastic, it will be surprisingly tough, but a JCB bucket is tougher. Personally, I wouldn't worry about breaking out 100mm, but you could always have a roll of duct tape handy for while you're waiting for Transco.

[AlexW]

Thanks for the info.

Taking another look tonight I think I can make out the line where the pipe goes under the 100yr old dry stone wall, at the edge of my property, this looks like it may have been "moled" or similar. Neigbhor reckons my house (end of semi-rural/rural road) only got gas less than

20 years ago.

Regards,

Alex.

[bof]

I've had to remove a lot of 4 - 6" thick concrete over the years, and lift and crack works really well so long as there's no reinforcing rods. I use a 3 - 4' long steel spike as a lever on a fulcrum of fence post or similar, stand on the steel spike to lift the concrete which only needs to rise 5 - 10mm or so, then hit the concrete with a sledge hammer to get liftable size pieces.