How to find down light cables in ceiling?

[Laki]

Hello
First time on this forum, I have had an extension done recently and the electrician has laid cables for around 30 down lights in the ceiling without drilling the holes trough. The ceiling is now plastered and painted and the electrician dissapiered together with the plans (if there where any).
Is there a way off uncovering the cables without destroying the ceiling?
Any help appreciated

 

[Echo the husky]

It will likely be difficult without the plans. 30 downlights!! That will be a lot of guessing. Where has the electrician gone and what does the electrician who is finishing the job say? I hope they aren't halogen lights!

 

[Iggifer]

I have had some success with a tester like this. (I'm sure you can get MUCH cheaper ones). You basically attach it to one end of the cable (probably at your switch) and it sends a tone down the cable, which the other part of the device detects and makes a noise.

I've only ever used it to find the odd cable that's got lost, for a fan etc. Never to that extent.

You may find that you will need to find one, then move the tester to the next cable etc. Depends if he's wired them in hard loops or not. You might be better off just biting the bullet and lifting the boards upstairs - here's to hoping there's access above!

 

[Laki]

Its a bit of a long story I wouldn't like to bite you withbut he is not gone exactly but he is not returning to the job. The current one says the same as you is going to be difficult!
Is there any technology that can aid in pinpointing the cable's? There are for LED spotlights.

 

[Echo the husky]

You might be better off just biting the bullet and lifting the boards upstairs - here's to hoping there's access above!

This will certainly save on having to make large numbers of repairs to the ceiling, and is probably the best way to start, but may not be possible if the flooring is chipboard.

It will be much easier if you know exactly where the joists are in the ceiling are, (this will certainly be more difficult now it is plastered and painted) and how many lights have been allocated for each room. You may be able to then make a good guess on the positions, at least you know where they could be between. If you are a bit off it can be difficult to then repair any damage around the downlight holes to a satisfactory standard.

The tone generator and probe linked to above often work ok, providing the cables aren't too far from the surface of the ceiling, I have that model and paid about £18 for it. They won't tell you if the cable is in the centre of the joists or right beside one though.

The final, last resort and most extreme option is to pull the ceiling down, make a new plan, then put up a new ceiling.

 

[Iggifer]

You might be better off just biting the bullet and lifting the boards upstairs - here's to hoping there's access above!

This will certainly save on having to make large numbers of repairs to the ceiling, and is probably the best way to start, but may not be possible if the flooring is chipboard.

It will be much easier if you know exactly where the joists are in the ceiling are, (this will certainly be more difficult now it is plastered and painted)

If it is chipboard, and even T&G to an extent. You should be able to determine which way they run, and where the joists are from the screws/nails in the floor above, so long as the screws/nails are actually in the joists

 

[Echo the husky]

Oh yes I didn't think of that! Must have left my brain behind again!

 

[Laki]

Thanks for the information
Lifting the floor above is not an option as it's a single storey extension with a flat roof. I think the cables have not been cut, they need to be uncovered than cut to connect the down light housing to each one. Does this affect the way yhe tester works? Would a inspection camera be of any use, drilling small holes and looking in to the ceiling?

 

[Iggifer]

Well with the tester I linked to, it would send the tone to where the cable has been cut. That may, or may not help. You will then have to cut a hole where the end of the cable is, find the next piece, and start again.

An inspection camera may help, but you need a starting point. Joists are generally 400mm centres, so depending on which way they run, there could only be a couple of joist spaces for the downlights to go in, or there could be loads....

 

[sparkwright]

As pointed out, not just a matter of finding the cables but also avoiding the joists.

You are bound to make mistakes - don't worry about the paint, just assume it's gonna need re-painting. Use a chalk-line to be certain the downlights are in straight lines where appropriate.

Can't you just ask the electrician for the ceiling plan??

 

[Laki]

Thanks for all the advice, I have been asking him for weeks but he and his boss have been fobbing me off, the boss is angry with me because I cut their work short due to various reasons. Main point is they're where paid up to then and no money was owed to them. There was no contract for the length of the job, and I was paying them weekly (in advance). It was taking longer than I could afford so I decided to finish the rest of the job myself. I didn't anticipate that they would take this badly. The last day they worked they where supposed to drill the holes in the ceiling, but when I got home I found they haven't. Now they won't give me the plan as to teach me a lesson knowing that I will have to damage the ceiling.
Hope this wasn't to boring. I will have to try some of the approaches mentioned probably the tester and maybe drilling test holes.

 

[Iggifer]

Was there no price agreed then? They were just on a day/week rate jolly?

 

[sparkwright]

Thanks for all the advice, I have been asking him for weeks but he and his boss have been fobbing me off, the boss is angry with me because I cut their work short due to various reasons. Main point is they're where paid up to then and no money was owed to them. There was no contract for the length of the job, and I was paying them weekly (in advance). It was taking longer than I could afford so I decided to finish the rest of the job myself. I didn't anticipate that they would take this badly. The last day they worked they where supposed to drill the holes in the ceiling, but when I got home I found they haven't. Now they won't give me the plan as to teach me a lesson knowing that I will have to damage the ceiling.
Hope this wasn't to boring. I will have to try some of the approaches mentioned probably the tester and maybe drilling test holes.

Shame.

I don't think I could be as spiteful as them.

Though I also wouldn't want to be kicked off a job.

It's virtually impossible to find one unknown downlight position, let alone 30 of them.

Best thing is to think about all the ways you can crawl, beg, and suck up to these people for the plan, IMHO.

 

[sparkwright]

Some useful tips;

Before drilling ANY of the downlight holes, ALWAYS make a small test hole with a bradawl, in the centre first, then imagine four 'corners' of the circle, and make test holes with bradawl here too.

By doing this, you can see if a joist is in the way.

Then angle the bradawl at each 'corner' to check a joist isn't too close by.

You can then get a stiff piece of wire, such as a coat hanger, to poke into the test holes to check there's no pipes or other obstructions in the way.

By doing all this, you may also hear or feel the cables, which will be reassuring at the least.

Do any photos exist of the ceilings before they were boarded?