Making good after re-wire

[unlucky]

Guys,

I'm re-wiring my house and getting it certified by a qualified sparky but wanted to ask you how deep the chases need to be from a plasterer's point of view to prevent any cracking/anything else that can go wrong with plaster (pardon the ignorance but I hardly know anything about it! too damn hard for me to do so I haven't picked it up at all!).

Is there anything I need to cover the exposed wiring with before the plasterer starts? joining tape etc?

I know how deep they need to be from a 17th edition and building regs point of view but don't really want to put them any deeper than I have too when considering both wiring regs and also the plasterers requirements.

Thanks in advance.

 

[joe-90]

How deep do they need to be from the 17th edition regs point of view? Or better still building regs? If you don't do them deep enough you'll have to do them all again won't you? Nothing to do with the plasterer is it?

 

[Micilin]

Just make sure all conduits are secure, so not moving , and everything is shy of the wall (ie nothing sticking out proud). No need to cover the conduits , joints etc as long as you can get enough plaster on them (at least 5-6 mm) If you have more than one conduit in the same chase, a gap between them will help the plaster grip and stop it blowing, otherwise you may be looking at mesh/wide scrim over them.

A good electrician will have all his wires curled into the boxes so that they are not sticking out . A tradesman (ie an electrician who has a bit more about him than certiificates) will do that as a matter of course, and may even sitck a bid of cardboard in teh box to make them easier to clean out.

Your plasterer will (again, if a tradesman and not just someone who can plaster) clean out all the boxes BEFORE his plaster finally sets and leave them nice and clean for the second fix. How well he does this usually depends on how nice the sparks was to him

 

[1john]

if you are using an angle grinder to cut the chases then you can angle the blade so the chase is wider at the back compared to the width on the wall (does that make sense) also cut the boxes as tight as possible with the angle grinder and run the grinder thorugh the middle of where the box is going, that way you get 2 x 1inch ish strips that break out easier.

Where in the regs does it state the depth for chases?????

Be aware that you cannot remove more than 1/3 of the thickness of the wall vertically and 1/6 horizintally. That is for the thickness of the skin, not the overall wall, so say you have 100mm brick with 10mm render and finish then you can only chase out to a max depth of 36mm vertically and 18mm horizontally.

 

[unlucky]

1john, I am using an angle grinder and that does all make sense.

The stipulation in the regs is partly what you said and partly the depth that cables need to be at before rcd protection isn't required. This isn't going to be applicable as I can't run every chase 50mm deep into the wall due to the depth restrictions in relation to the overall skin thickness.

It was more a question of how deep the chases need to be in order to get the plaster on so it will grip and not blow or crack etc, bit confusing from how I originally wrote it. Sorry.

Thanks for the responses.

Phil

 

[PrenticeBoyofDerry]

Chase the plaster out, until you reach the bare brick/block work behind.
Then you can clip direct to the wall to fix the cable, you can also consider using plastic capping over the cable, to prevent trowel damage when you fill the chase, it's not a must do providing the cable in the chase is below the finished wall level.
If it's plasterboard wall you will need to feed the cable behind the board.
You will be aware of the min 50mm depth or the use of mechanical protection, in relationship to the RCDs.
I don't believe the the one third or one sixth depth applies to the wall including, render/plaster, they are not structural. but does apply to the brick/block work.

So no need for an angle grinder, hammer a bolster will do.

 

[Richard C]

you can also consider using plastic capping over the cable, to prevent trowel damage when you fill the chase

I always use steel capping rather than plastic as it offer a degree of protection to drill wielding DIY enthusiasts. The most determined will still get through it eventually but it could provide just enough resistance & time for the "penny to drop" as to why the drill won’t penetrate.

I promised myself I wouldn’t go on about the trowel damage myth any more.

 

[unlucky]

Guys, thanks for all the responses.

You don't need to use steel capping from a regs point of view in relation to chases to switches and sockets as long as the cables run in the safe zones.

Outside of this you do need to cap the wires though, so I'll be doing this when running the cables for the upstairs ring main and lighting circuit in the kitchen wall as there will be no evidence of cables in the wall but this will be behind plasterboard.

Cheers everyone.

Phil

 

[Richard C]

You don't need to use steel capping from a regs point of view in relation to chases to switches and sockets as long as the cables run in the safe zones.

Correct but I always cap because it makes for a neater job IMO & I always use steel capping purely for the reson I stated; choice is yours really.

You can only run cables within designated safe zones unless you provide mechanical protection (conduit) capping is not suitable.

 

[Micilin]

I wish capping was banned and we went back to chased - in conduit.

Plasterers have been subsidising lazy electricians for years!!!!!!!

 

[Richard C]

I wish capping was banned and we went back to chased - in conduit.

Plasterers have been subsidising lazy electricians for years!!!!!!!

& they reckon we hack their cables to death with our precious & perfectly honed trowel when we plaster ; damn I said I wouldn't be going on about it again

 

[roughcaster]

I wish we went back to chased - in conduit.

That was the best way ever!!!
Some of the capped cables nowadays, are so near to the surface, that they are just about covered. At least with the old conduit system,, set well back into a chase, there was never any problem.

 

[Micilin]

I wish we went back to chased - in conduit.

That was the best way ever!!!
Some of the capped cables nowadays, are so near to the surface, that they are just about covered. At least with the old conduit system,, set well back into a chase, there was never any problem.

Plus they exaggerate bad blockwork, they are often badly fixed and so move when plastering . We have to mix more, spread more just so the sparky has a easy life!!!

 

[unlucky]

OOOO,

Can of worms sucessfully opened!!

I'll be placing all the wires inside oval conduit so its easier to plaster and can be pulled out and re-wired. Slightly odd, but it will be easier for the next sparky that comes to it and thinks, "that guy put conduit in so I could save chasing the walls, how nice!!"

Plus its cheaper than capping.

Cheers guys

 

[Richard C]

Plus its cheaper than capping.
Cheers guys

Think the guys are talking proper steel conduit, not the cheap plastic stuff in B&Q; you know, as still use on industrial installations