Risk of chipping incoming electricity

[wretan]

Hello,

I'm planning to break up the cast slab in the bathroom of our fifties villa (row house) for a bathroom renovation, and the slab seems to be about 20cm.

According to the drawings, we have incoming electrical wiring right underneath the bathroom. But how deep can the cable be? It's not fun to hit the cable directly with the demolition machine.

Or do you think the incoming cable is in the gravel/sand far below the slab?

Is there any way to measure where it lies?

I'm attaching the drawing; the bathroom is in the circled corner of the rectangular building.

What do you think?

Best regards,
Johan

 

[Banvaktarn]

I would not trust that drawing, the cable is guaranteed to be drawn schematically and not in the true position, rent a cable detector.

 

[rävlyan]

The year on the house is the 50s, normally the plumbing and electricity are in the masses under the slab, and not cast into it. It's likely that in your case, they are deep. How much do you need to remove, all of it? There's probably a lot of reinforcement in that slab, likely single reinforcement. One way to see is how deep the kitchen drain goes down, then there is an indication of how it looks under the slab, what the depth of the pipes is, and then it's the same for the electricity.

 

[wretan]

I wouldn't trust that drawing, the line is guaranteed to be drawn schematically and not in true location, rent a cable detector.

Good idea, I'll check with the local rental if they have one. It's a pretty cheap insurance in that case. I've tried the cheaper home versions but they're completely worthless. You're most likely right that the drawing is schematic.

 

[wretan]

The house dates back to the 1950s, typically the sewage and electrical are in the masses under the slab, and not embedded in it. It is likely that in your case it is deep. How much do you need to remove, everything? There is probably a lot of reinforcement in the slab, probably single reinforcement. A way to see is how deep the kitchen drain goes down, then that gives an indication of what it looks like under the slab, what the depth of the pipes is, and then it's the same for the electricity.

Thanks for the great input! I guess I have to remove quite a bit more as I need to get down to the sewage stack that's down there since everything will be rearranged in the new bathroom. But as icing on the cake, the outgoing drain towards the street is exactly where we need to chisel away, so it will be exciting to see how everything is connected.

If I can just safely chisel away 20cm of the slab, I can take sand/gravel ala archaeologist carefully with a brush without the risk of cutting the cable.

I agree it sounds unlikely that the cable is in a 20cm slab, but perhaps they did things differently 70 years ago...

 

[rävlyan]

I have not seen these conduits in the slab during the years I've been in construction, except when there are two floors. Most often, the plumbing to the kitchen is in the joists or goes down the wall to the lower floor, or just straight down. The electricity comes in on the outer wall by looping around the house to the meter cabinet. If the meter cabinet is on a pole, the cable takes the shortest route to the electrical panel. There may be exceptions, but not likely in your case.

 

[rävlyan]

Edit, you can probably forget about finding a cable under a slab with instruments, it is probably deep with reinforced concrete between the instruments and cable, if it's in the slab it might work.

 

[Banvaktarn]

Edit, forget about finding a cable under a slab with instruments, it's probably deep with reinforced concrete between the instruments and the cable, if it's in the slab it might work

There are locators for cables in the ground, I own one myself, if there are multiple cables, there are clamps you attach to the cable you want to search for if they go in different directions in the ground.

 

[JoelN]

Where are the meter fuses?

 

[wretan]

Ok, thanks, that sounds great and just the answer I had hoped for

I would also think that the cable takes the shortest route from the electrical cabinet under the neighbor's house.

The residential building itself has a crawl space 50cm above ground level but the garage section where the bathroom is has a concrete slab 50cm lower. I don't know if this might affect the cabling between the neighbors?

 

[rävlyan]

Under the neighbor's house ??? don't think so, did the house exist before or after the electricity to the house you are talking about?
There is a good way to find out, contact Ledningskollen, you register online
It is free of charge and everyone who might have something in the ground will tell you where theirs are
Say that you are going to dig for a new foundation along your house
Hopefully, your meter cabinet is on the house wall then

 

[wretan]

Where do you have the meter fuses?

On a wall just outside the proposed extended bathroom. The cable goes straight down into the ground there.

Pretty much right at the triangle marking on the drawing.

 

[rävlyan]

Perfect, then you can find out where the cable is leading to the meter cabinet, it's not your cable.

If you're home when they come, you can ask; you can see how it goes toward "something."

They are usually not reluctant to help.

Ask them to contact you when they are coming, but sometimes they provide a drawing, those exist with the network owner, and if not, they are obliged to come out.

 

[wretan]

Under grannes hus ??? tror inte det, fanns det huset före eller efter el till det hus du pratar om?
There's a good way to find out, contact ledningskollen, you sign up online.
It is free of charge and everyone who might have something in the ground will let you know where theirs is located.
Say you are going to dig for a new foundation along your house.
Hope that your meter cabinet is on the house wall then

Yep, the whole row of houses was built at the same time.
I have an earlier drawing where house number three has incoming from the street and then a cable goes up to the neighbor (house two), our house (house one), and similarly to house four and five.

The drawing I attached I got via ledningskollen, really convenient!

 

[rävlyan]

I probably missed something, is there another house (owner) located at the bottom of your drawing?
If so, you don't need to worry about there being any cable in the slab or at digging depth.
It's probably securely in pipe/slang about 60 cm below the surface and maybe together with VA
in the same trench, and then it's deep.