Cabling in Walls

[androiduk2002]

Ok as you know I an new to the trade and trying to learn well ahead of my time in am sure but I have questions.............where better to ask them .

When chasing cables into walls how deep you do go ? I know the OSG quotes 50mm but is that the standard ?

After chasings do you then clip or is this done by the use of capping ?

I am sure I might learn the "right way" at college in time but things are not always possible the "right way", also be it right or wrong I have been looking at the screwfix catalogue and only one of the wall chasers cuts deep enough to achieve 50mm ?

If its a new build do you go 50mm into bare block work (some do still build proper houses )or do you allow for plaster ? and set it at say 45mm ?

Thanks in advance.

 

[Lurch]

It doesn;t have to be 50mm, it just has to be RCD protected if it isn;t.

 

[androiduk2002]

So how do you determine what is best , by depth of wall ?

Do you RCD even if it is 50 mm ?

 

[Lurch]

In most cases the cable will be <50mm from the surface so it's easier to RCD protect the circuit than it is to get every cable >50mm deep. Most circuits would be RCD protected anyway as even under the 16th edition you would generally RCD all sockets, shower, cooker and other power circuits.

If it doesn;t need an RCD then I don;t RCD it, some people RCD everything, some people do a bit of both. It depends on the installation, circuit types, intended use, operators etc... far too broad a question to answer easily.

 

[septiclecky]

Can't remember were it was but there is a notice off how deep you can chase walls due to the weaking effect on them by chaseing. It's the same for drilling holes in joists.

 

[batty]

Not a good idea to chop cables that far in a wall just use capping or if you do want to chop them in use galvanised conduit thats earthed. I do this on cooker circuits. the rest are RCBO protected.

batty

 

[spinlondon]

This was posted by Bez in the TV on a wall thread.

"Building regs say max 1 third of the wall thickness for vertical chases, 1 sixth for horizontal chase."

 

[Evans Electric]

Android, you dont want to be chasing cable drops in walls at 50mm deep, Thats 2" inches remember, the bloody house will cave in . Or the builder will sue you for damages. Just the usual sheathing with RCDs on everything

Deke

 

[androiduk2002]

why is it not a good idea ? because of weakening ? mess ? time taken ? see this is the kind of knowledge only achieved by working on site/in the trade, something i wont be achieving for a while

 

[androiduk2002]

Point taken so what depth do you chase to ? is there a standard or guideline or is it to the individual ?

 

[batty]

why is it not a good idea ? because of weakening ? mess ? time taken ? see this is the kind of knowledge only achieved by working on site/in the trade, something i wont be achieving for a while

You will never do it in a fletton brick wall ie 50mm, hard enough just getting cables below plaster.

 

[batty]

Point taken so what depth do you chase to ? is there a standard or guideline or is it to the individual ?

I have a makita chase cutter this cuts 30mm chase this is usually adequate for conduit on rewires.

 

[Lurch]

why is it not a good idea ? because of weakening ? mess ? time taken ?

All of that.

If you chase all cables in >50mm then you're going to end up with no structural integrity in any walls, and a lot of walls will be <100mm thick anyway so it would be impossible to get the cable >50mm deep.

If you can get cables 50mm deep then it is a lot of extra, mostly unneccesary, work. It's not worth the effort and time just for the sake of not RCDing something that doesn't matter either way. It is generally easier to have some sort of earthed sheath (galv conduit or MICC cable etc...) rather than sink all cables. I can;t see the point in the 50mm rule anyway as once you've chased it in it will be covered in plaster, so if I was screwing into the wall I would keep going until found something solid and use 4" screws, so sort of defeats the object. Safe zones were fine, and the RCD everything\>50mm rules are a knee jerk reaction to a problem that never existed.

Point taken so what depth do you chase to ? is there a standard or guideline or is it to the individual ?

However deep you need. usually you'd chase back to brick on a rewire, or fix to blockwork etc... on a new build. No set depth as such, <50mm is <50mm regardless.

 

[SPECIAL LOCATION]

Ok as you know I an new to the trade and trying to learn well ahead of my time in am sure but I have questions.............where better to ask them .When chasing cables into walls how deep you do go ? I know the OSG quotes 50mm but is that the standard ?

After chasings do you then clip or is this done by the use of capping ?

I am sure I might learn the "right way" at college in time but things are not always possible the "right way", also be it right or wrong I have been looking at the screwfix catalogue and only one of the wall chasers cuts deep enough to achieve 50mm ?

If its a new build do you go 50mm into bare block work (some do still build proper houses )or do you allow for plaster ? and set it at say 45mm ?

Thanks in advance.

The OSG does NOT say you have to chase cables to 50mm!

but it does give guidance when RCD protection is required.

Building regs Approved Document A (paragraph 2C30 my guide book says.)

Vertical 1/3 thickness of the wall.

or with cavity walls 1/3 thickness of the leaf.

Horizontal no deeper than 1/6 thickness o the wall or leaf.

AND

chases should not impair the stability of the wall particularly where hollow bricks are used.

so if you did want to go 50mm leaf of wall must be 150mm 6" for vert

or 300mm 12" thick for horizontal chases.

Bottom line is.....

Just chase the plaster depth!

A lot of walls now are dabbed & dry lined, nice bit of oval conduit sits behind this quite fine IMHO!

Guinness

 

[SPECIAL LOCATION]

Android, you dont want to be chasing cable drops in walls at 50mm deep, Thats 2" inches remember, the bloody house will cave in . Or the builder will sue you for damages. Just the usual sheathing with RCDs on everythingDeke

:^O :^O

 

[Evans Electric]

Think about it , Android, cutting a channel 2 inches deep in brickwork or loadbearing blocks, what a load of hard graft and then the architect could turn up and say the electrician has weakened the structure of the building , is he insurered ? You'd be there forever cutting channels that deep.

Now if the walls were partitions and the cables could go in at 50mm , thats different.

 

[androiduk2002]

See this is why I asked

Last thing I want to do is bring the house down when the time comes.

ROTFWL ROTFWL

 

[a1]

That's why we are here and always pleased to help, where possible.

With regard to block work on new builds, you could have the cable coming down on the drop, un-clipped and cover it/them with you cable channelling. This; remember, is only there to protect your cables from the plasterer's trowel.

It also makes any future re-wires much easier, as you will find with the old houses that contain the old metal channelling.

 

[Andy™]

also remember that if you do chase the cable 50mm into the wall, the cable will most likely be less than 50mm from the other side.... added to the fact the wall will have lost a lot of its strength

 

[androiduk2002]

So to clarify what i am reading , on new builds run cable down block work and cap directly on block work plasterer will cover up later , on rewires chase back to brick/block work run cable the cap then make good . So you dont actually chase into the brick/block work for normal T&E work ?

Just to make sure im totally clear lol