Routing lighting flex through a wall

[IfInDoubtDIY]

I’m planning out the replacement of an external security light (see my numerous other posts related to this job lol) and I have come to the conclusion that it’s probably more in my interest to drill through the wall and run the cable through that way, rather than trying to faff around with the existing wire (Twin and Earth) while at the top of a ladder!

My plan is to buy a long masonry drill bit (16mm) and then go through the wall from the outside (I know I need to go in at a slight upward angle), then the wire can go through.

My first question is whether I should “line” the channel with anything? I’ve heard that some people use PEX Pipe for this purpose, is this absolutely necessary or can I just feed the cable through?

My next question is whether it’s better to put a junction box on the outside of the wall and feed a cable through from there, rather than wiring the light to a JB on the inside? My thinking here is that once I drill that hole it’s going to need sealed with silicone and that may make it difficult to remove or replace the light in the future.

 

[trojanhawrs]

Having your connections inside is always going to be better than out if you can. If you're putting a 16mm hole in buy some rigid 16mm pipe and hammer it through the hole. Silicone is not really necessary if your hole is angled so the water can't enter, once connected shove a bit of paper/kitchen roll in from the inside and expanding foam from out. Just watch when you're buying your new light as some come with ridiculously short prewired cables, get something that's going to make it inside comfortably

 

[ebee]

Drill the hole not level but down on the outside to allow water to run out. Seal on the inside. Put a liner , such as a piece of plastic pipe or conduit to give the cable/flex some mechanical protection from the wall/snots etc.
Before your drill breaks thru on the outside take hammer action off for the last bit and use only light pressure , that reduces your chances of breaking off a big wedge of wall on break thru.
Nicely sealed will prevent not just moisture but insects too.
Depending upon whether prewired or you need to add flex will determine where you put junctions (inside is best if possible)

 

[IfInDoubtDIY]

Thanks @ebee and @trojanhawrs. Hopefully sealing the end won’t make it too difficult to remove the light if needed. The light fitting I have in mind has a 75cm cable attached - and my garage wall is only about 22cm thick so I should have plenty to work with!

 

[chivers67]

16 mm is a bit overkill, use a 10mm drill bit if you're using flex, a good make of silicon should be enough to weather proof the hole or use a Wall Grommet if the flex you're using is thin enough.


This link might help

 

[ericmark]

I had a problem with sister's house, there were insulating little balls in the cavity. I had to squirt in expanding foam in, allow it to set, then re-drill the hole.

 

[IfInDoubtDIY]

16 mm is a bit overkill, use a 10mm drill bit if you're using flex, a good make of silicon should be enough to weather proof the hole or use a Wall Grommet if the flex you're using is thin enough.


This link might help

Thanks. I chose 16mm as I want to line it with 15mm pipe. Perhaps I don’t need to then?

 

[chivers67]

No I personally don't think you need to.

 

[IfInDoubtDIY]

No I personally don't think you need to.

Ok, that’s good to know. Might make things a bit easier. I’m remembering when I got broadband installed, they just fed the fibre optic cable directly through the wall when they did the installation, without lining the channel with anything.

 

[trojanhawrs]

I had a problem with sister's house, there were insulating little balls in the cavity. I had to squirt in expanding foam in, allow it to set, then re-drill the hole.

What you can also do in this case it's leave your drill bit in and knock it out with a pipe to take it's place

 

[endecotp]

You don’t need to line the hole, and 16mm is much larger than necessary.

 

[IfInDoubtDIY]

You don’t need to line the hole, and 16mm is much larger than necessary.

Ok, you’ve convinced me. I’ll get a 10 or 12mm bit and just feed the cable directly through.

 

[Ragnar_AT]

For 0.75 mm2 flex an 8 mm bit should be well enough.