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I'm about to drill some 5mm diameter x 35mm deep holes to support a new curtain rail and when I used a voltage/metal detector to check for cables etc. it gives an alert for the entire surface of the wall. Is this possible and does it mean there may be a problem with the electrics in the flat?

Possible things I have thought of are:

The detector isn't calibrated correctly. I have calibrated according to the instructions The wall paint is conductive.

What should I do?

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What is the wall made of and what type of detector are you using? I would suspect a false positive in that it is extremely unlikely that the entire wall would be energized without other much more noticeable issues. – Comintern Apr 12 '14 at 14:40
The wall is drywall, but the full construction I don't know. I have only just moved in and so don't know the paint and any other preparation before I arrived. The drywall knowledge is based on other walls that I have stripped for decorating, one of which is the wall adjoining and behind this wall that I'm getting the strange readings. I'm using a Silverline 3-in-1 detector that does Metal/Voltage on one side and Stud detection on the other side. – Johnny Maelstrom Apr 21 '14 at 17:44

If you're using a metal detector maybe your wall is plaster on wire lath, there's such a thing as electric heat elements embedded in walls or maybe steel studding. You need to know what your wall construction is, and do you mean 3.5mm holes for screws?

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I did some recalibration, changed the battery and generally spent more time on this and it is not the full wall that is the problem. There is a roughly 1 metre-square section of the wall that triggers the detector. It seems to be consistently metal now rather than voltage and metal alert that it was before. Without a lot of understanding about wire lath, would this be consistent with that? Does that mean I am likely to be safe to drill? – Johnny Maelstrom Apr 21 '14 at 17:47
I rushed in the original post previously and meant that I intended to drill to a depth of 35mm. I was concerned with whether the depth would help in diagnosing the problem, i.e. whether or not that depth would be safe or not depending on the underlying problem. – Johnny Maelstrom Apr 21 '14 at 17:50

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