Twin & earth routing though a wall.

Grant_ · 19 Jan 2021

Hi all.

I'm sure this has been asked before, but searching returns hundreds of results about routing cable inside walls) though chases etc.

In my garage there is a length of 6mm t&e ending at a 45a terminal block. I'd like to switch this for a commando socket in the car port in the other side of the wall.
There's an isolator switch roughly inline with where is like the socket, but higher up.

I'm thinking drill a 16mm hole at about 45 degrees so there is no hard 90degree bend IN the cable. Then just put the socket over the hole on the outside. Would have preferred to drill outside in so as to not chip the harling but there a water pipe to the garage tap within a few cm so don't want to run the risk that I've got the measurement wrong or that the drill goes squint.

Also thought about either conduit or SWA cable then going down to the bottom of the wall, though the brick and back up, but wouldn't be able to maintain the bending radius on this. Just curious if there are other ways to do this? Short of knocking bricks out.

Tigercubrider · 19 Jan 2021

drill a narrow hole inside out, use your judgement when near the outside. Then use the larger drill outside in (or at least halfway)

Grant_ · 19 Jan 2021

Thanks.
Problem is that it's a double skin brick/breeze block wall. I've got a 14mm 46mm long bit which is just about long enough to go though the wall straight on.
Will probably need a 1m long bit too go though the wall at an angle.

Might end up drilling a hole lower down clear of everything just to use as a point of reference.

Also can't find anything on whether the bend radius of t&e is different on the flat side.

Tigercubrider · 19 Jan 2021

long drill bits are cheap
https://www.wickes.co.uk/Wickes-SDS+-Drill-Bit---10-x-450mm/p/215636

Grant_ · 19 Jan 2021

Yeah I know.

Like I say though, The wall is to thick to use a 460mm drill. Looking at 1m long stuff I've but be able to find anything small

Simon35 · 19 Jan 2021

Grant_ said:
Yeah I know.

Like I say though, The wall is to thick to use a 460mm drill. Looking at 1m long stuff I've but be able to find anything small

Thats a very thick wall! Are you sure?

JohnW2 · 19 Jan 2021

Simon35 said:
Thats a very thick wall! Are you sure?

450mm isn't quite long enough for some of my walls.

Kind Regards, John

333rocky333 · 19 Jan 2021

Cannot vouch for the quality but I see these when i was working in the store

https://www.therange.co.uk/diy/powe...iece-1000mm-sds-masonry-drill-bit-set/#162468

https://www.therange.co.uk/diy/powe...piece-450mm-sds-masonry-drill-bit-set/#162469

Grant_ · 19 Jan 2021

Simon35 said:
Thats a very thick wall! Are you sure?

The wall is breeze block, cavity then brick & harling.
Looking at the window the wall is approx 30cm.

Gone back to high school maths that puts the drill should reach 42cm. As long as the walls not any thicker.

Wife's still reticent about me doing this myself and wants me to hire a spark. Will see how it goes ,

Mind you I probably won't get it bang on 45 degrees

Simon35 · 20 Jan 2021

Grant_ said:
The wall is breeze block, cavity then brick & harling.
Looking at the window the wall is approx 30cm.

Gone back to high school maths that puts the drill should reach 42cm. As long as the walls not any thicker.

Wife's still reticent about me doing this myself and wants me to hire a spark. Will see how it goes ,

Mind you I probably won't get it bang on 45 degrees

In your earlier post you said...

Problem is that it's a double skin brick/breeze block wall. I've got a 14mm 46mm long bit which is just about long enough to go though the wall straight on.
Will probably need a 1m long bit too go though the wall at an angle.

Is the wall 300 thick or 460 thick?

Not sure why you need it at 45 degrees? If the wall is 300 thick, angle down at 30 degrees, and drill out. Stop before you get all the way through, then go from the outside for the last bit to stop the outside finish spalling off.

Grant_ · 20 Jan 2021

I was guestimsting.
Basing on putting the dryer hose into the existing vent last week and my arm disappearing up to the elbow to reach the partially inserted dryer hose, and so assuming that drilling on an angle the 460mm bit may not be long enough.

Last night I measured the window ledges, they are about 11.5 cm each so dependibg how thick the window is probably puts the wall between 30 & 35.

Your right it probably doesn't need to be at 45 degrees I think that came from a post I read about SWA and it's rather large bend radius.

JohnW2 · 20 Jan 2021

Simon35 said:
Is the wall 300 thick or 460 thick? .... Not sure why you need it at 45 degrees? If the wall is 300 thick, angle down at 30 degrees, and drill out. ...

As the OP has implied, if the angle is less than 45° (indeed, even if it is 45°), there is a problem IF one wants to comply with the recommended minimum bending radius for SWA - and, as the OP's maths has correctly concluded, a 45° hole through a 300mm wall would be about 420 mm long. I know what I would probably do, but I'm not going to 'recommend or advise' it

Simon35 said:
... Stop before you get all the way through, then go from the outside for the last bit to stop the outside finish spalling off.

An excellent idea but, other than for people a lot more clever/skilful than me (and particularly when one is not drilling exactly horizontally), that presents a next-to-impossible 'aiming problem'

Kind Regards, John

333rocky333 · 20 Jan 2021

Get a big lump of ply and wedge against the wall outside, you will hopefully hit that and know before breaking right through, then go round and drill back in.
Not sure what Harling is but dont blame me if you damage it

333rocky333 · 20 Jan 2021

JohnW2 said:
. I know what I would probably do, but I'm not going to 'recommend or advise' it
'

Intrigued by that comment PM me the answer please

JohnW2 · 20 Jan 2021

333rocky333 said:
Not sure what Harling is but dont blame me if you damage it

As I understand it, essentially a type of 'pebbledash' applied to the outside of walls - hence pretty easily damaged if one drills through it from inside.

I think the word "hurling" probably originates from the fact that small stones/pebbles are 'hurled' at wet mortar!

Kind Regards, John

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Twin & earth routing though a wall.

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