Finding mains wiring inside walls

[Matty F]

I need a way of tracing wires inside exterior walls and celings. The walls have timber frames wih plasterboard (i.e. with a cardboard surface and a gypsum core) on the inside, polystyrene foam insulation, building paper and weatherboards.

I do have a stud finder but that is useless on exterior walls because the outside of the plasterboard has aluminium foil on it, and the wires are beyond that. The stud finder emits a continuous beep within a foot of all the outside walls.

A radio tuned off station works well but not where there is foil.

If I buy some device there is no guarantee that it will work past the foil.

Maybe I could use a solenoid connected to headphones.

[Manticore]

If you know any telephone engineers, ask if you can borrow their "tone and amp". It's basically a signal generator that produces a 1Khz signal. After disconnecting the mains wiring from the power (ONLY use this on DEAD wiring, NOT LIVE), connect the "tone" (as it's affectionately known) to a pair of wires and you then use the amplifier to listen for the tone and trace the route.

This is a bit expensive for a trial in case the foil masks the tone (hence my suggestion to borrow one first) but this is the sort of thing

[Jules Richardson]

Put up some shelves. Nothing detects wiring quite like the process of screwing shelf brackets to walls. ;-)

(I sympathise, by the way - I have the same problem at our house. I was just trying to trace some of the older wiring last week, too, with a view to replacing it - so being able to find an exact path would be handy for me as well)

cheers

Jules

[Frank Erskine]

Maplin do a similarish one, but a lot cheaper.

[Camdor]

Tone generator won't work through the foil. You need to get a Cat & Genny. You can Hire them

[Matty F]

them

radio seems to work quite well through the weatherboards.

[Frank Erskine]

them

>>> --

q.v. :-

[Manticore]

That depends - it may do or it may not. I can still hear the tone well, even when working on screened telephone cables so the tone does penetrate through _that_ foil. My only concern in this case is that I don't know how thick the foil backing on the boards is, nor how deep the cables are beneath the foil.