Running cables in wall

[Flip20]

Hi

I have a single leaf thermalite wall between a utlility room and garage that I have reinforced by building a wooden stud framework on the garage side. This will be covered with plaster board.

To run the cables from new light switches on the utility side I was planning to run the cables through the thermalite block and up the inside of the cavity created by the stud work on the garage side. This way I don’t have to chase the wall out in three places and risk weakening it.

Is this acceptable?

How does the maximum 100mm wall thinkness for safe zones on opposite sides of walls apply in this situation? The thermalite is probably just under 100mm thick but the total thickness (plaster + thermalite + studding + plaster board) closer to 180mm. Are the wires considered to be in the wall or on the other side of the wall?

Another couple of points which might be relevant. The top of the stud work is visible (there’s no ceiling in the garage) so the cables could potentially be seen entering the studwork from the top. The stud work cavity is 60-70mm deep.

Any advice appreciated.

Cheers
Mark

 

[ban-all-sheds]

To run the cables from new light switches on the utility side I was planning to run the cables through the thermalite block and up the inside of the cavity created by the stud work on the garage side. This way I don’t have to chase the wall out in three places and risk weakening it.

Vertical chases for light switches won't weaken it unduly.

Is this acceptable?

Probably not - depends how easily the positions of the cables can be determined from the other side.

How does the maximum 100mm wall thinkness for safe zones on opposite sides of walls apply in this situation?

What 100mm thickness?

Another couple of points which might be relevant. The top of the stud work is visible (there’s no ceiling in the garage) so the cables could potentially be seen entering the studwork from the top.

Still a little flaky.

If it's a garage, why not run the cables on the surface?

• http://www.voltimum.co.uk/files/gb/attachments/niu/l/attachments/c5-43.pdf
• http://web.archive.org/web/20061110111450/http://www.niceic.org.uk/downloads/concealedcables.pdf
• IEE article
• IEE Article on 17th Edition requirements for concealed cables.

 

[Flip20]

Thanks for the reply

I was refering to the 100mm mentioned in the pdf of your second link.

"This zone now extends to the reverse side of a wall or partition of
100 mm thickness or less if the location of the point, accessory
or switchgear can be determined from that reverse side."

There is a door in the wall so the position could be determined but total thickness is greater than 100mm so I guess this doesn't apply.

I was planning to mount wall units on the garage side so trunking would get in the way. There are also 5 light switches for utility and outside lights and a single socket so a few runs.

What if I secure the cable to the back of the thermalite with capping so it's more than 50mm from the plaster board?

 

[1john]

vertical chases will hardly compromise the integrety of the wall, they will be easy enough to cut into thermalite. they dont need to be very deep. I beleive the relevent regs state that you can chase upto 1/3 of the overall depth of the wall vertically and 1/6 horizontally.

 

[electronicsuk]

If the overall thickness of the wall (including studding and blockwork) is >100mm and you can guarantee that your new cable will be >50mm deep behind the plasterboard, I see no problem with what you propose.

In fact, the overall thickness of the wall is pretty irrelevant as long as you can guarantee burial (or clipping behind studwork in this case) at a depth of greater than 50mm.

 

[Taylortwocities]

Your new cabling will, of course, be RCD protected?

 

[ban-all-sheds]

The stud work cavity is 60-70mm deep.

Missed that bit.

Cables clipped to the blockwork will be >50mm deep, so there are no zone restrictions.

Or RCD requirements.

 

[Flip20]

Thanks all

They'll all be going under RCD anyway as new consumer unit going in shortly.

That's a releaf wasn't looking forward to another night covered in concrete dust as I discover more large chunks of loose plaster on each side of the chase.

Mark