Threading a lighting cable through a old-style cavity wall

[RogerS]

For that read 'lath and plaster'. The red arrow marks the spot but the actual entry point for the wire is tucked way down and nearly inaccessible.




The Problem

SWMBO had bought a wall-light for the en-suite. I originally thought that I could run the lighting cable down from the ceiling/wall junction to the light via some small plastic ducting fixed to the wall. It was then that I realised that the light fixed tight against the wall with no way of getting the wire, when fed over the wall surface, into the back of the light fitting. Yes, I could still run the wire down inside the trunking, get a Dremel out and grind some of the plaster away to sink the wire into. Trouble with that would be the unknown depth of the plaster and would it be enough before I started hitting a lath. Basically chasing out a channel in lath and plaster is almost certainly doomed.

Possible solution

On investigation in the loft I realised that the wall was lath and plaster and on the other side was a cavity.. But how to thread the wire down and back out. If it was a pattress (back box) being fitted to the lath and plaster wall then that would have given a nice wide opening to ferret around in to catch the wire that had been fed down in the cavity. But it isn't and the lamp is only about the size of a 2p piece where it touches the wall. And then .......

Final solution

If I gently cut a small hole through the lath and plaster using a sharp Forstner bit then that would give me some access albeit small. You can just make out the hole in the ceiling for the original wire routing,



I then taped a magnet to the end of the wire



Back in the ensuite, I stuck a big lump of steel to act as magnet bait and hopefully providing better attraction than any nails in the lath and plaster. AKA chisel


Gently fed the wire down the cavity and felt the slight tug when it attached itself to the chisel...you can just make out the wire



Judicious use of tapering pliers et voila

 

[AndyT]

Ingenious! And I bet it felt very satisfying when it worked.

 

[duke]

Worked well Roger, with only a small hole to repair.

 

[RogerS]

Worked well Rodger, with only a small hole to repair.

Doesn't even need to be repaired as it is hidden by the lamp fitting.

I have to hand it to LOML. 10/10 for choosing style. 1/10 for ease of fitting. It has two bulbs - one shooting upwards and one down. The latter is relatively easy to fit the bulb - a G10. The top one ? You can't see it and can barely get your hand into position. My bad as I didn't factor in where the screw holes to fix the lamp would go - when I drilled that large hole for the wire. I ran out of four letter words. I think I'll not say anything to her and see if she notices.

 

[Lons]

The magnet is an old well used trick, I have a couple of rare earth type magnets fixed to srtrong string and they've been used many times.

 

[Pete Maddex]

I have used a tape measure in the past.
You feed in a loop of tape by pushing the tape in at a sharp angle so it spreads out in the cavity and drop a weighted string down past the tape and pull the tape out. It works very well even if it’s misaligned.

Pete

 

[fuse]

Ive used the neodymium magnet from an old hard drive and the ball of an old mouse ( go on ...) on either side of ceiling plasterboard to identify drilling points for recessed lights,avoiding joists in the process.