How do you embed exposed main wiring into wall


Postby jcwalker » Thu Feb 28, 2008 11:03 am

I have a couple of electrical points in my flat where the wiring goes over the wall (both from the ceiling and from the floor) and is hidden by plastic trunking. I want to get these wires behind the wall somehow. Is it possible to 'embed' them into the wall (i.e. by creating a channel for them in the plaster)? Presumably they would still need a gap around them, so possibly could embed the plastic trunking into the wall and plaster over?
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Postby kbrownie » Thu Feb 28, 2008 12:40 pm

jcwalker,
The cables can be burried in the walls, but there are guidelines to follow when doing this. The cables have to be protected from mechanical damage ie someone hanging up a picture and screwing into the cable or hammering a nail through it.
There are permitted routes which cables can be run, which are in a direct line horzontally and vertically of a socket-outlet or switch, or within 150mm from top of the wall horizontally, within 150mm of angles formed by two wall vertically, these areas are detailed in the on-site guide.
They can also be burried at least 50mm from the surface of a wall (that's both sides of wall or protected by metal caps or metal trunking.
regards
KB
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Postby jcwalker » Thu Feb 28, 2008 1:58 pm

Thanks KB. So, metal trunking best for safety, and follow a direct vertical line (in my case). Any suggestions on how to actually create the channels in the walls? Just drill a series of holes down the line and excavate with hammer and chisel?
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Postby ericmark » Thu Feb 28, 2008 10:10 pm

There are special tools that cut two groves then one can simply chisel out plaster between the two groves. Using a chisel without cuts first is likely to remove more plaster than you want so to lines need marking and cutting so the plaster being chiseled out does not take the plaster alongside with it. There are assorts of methods from hack saw blades or pad saws to just marking with chisel first which is used will depend on the condition of the plaster and finishes applied to the wall paint etc. Without some experience in judging one can make one hell of a mess.
The most likely method would be to used the existing service trunking as a guide and make a cut either side then temp remove it or displace it while chiseling out plaster that was behind the trunking then replacing it in the grove but it requires on site judgment as to best method and you could very easily make a real mess and I would advise not really a DIY job.
Steel conduit tends to be round and getting this behind thin plaster is not easy. Plastic conduit can be oval and a lot easier to hide behind plaster. Capping is normally only used when the whole wall is stripped of plaster as it needs wider channel, metal capping will not stop nails and is only any real help to plaster as it flexes less and has no real extra protection for the cable. There is some debate to once new regulations come in as to if it will need earths connecting to it.
Often one finds cable is too short to bury unless the box is also moved.
All in all I would not recommend DIY if the walls are stud walls and not plastered brick or brease block or lath and plaster then methods completely change. Consideration on wall thickness especially if less than 100mm finding where the wood is drilling and threading cable which means it must be disconnected giving the dangers associated with that. There is a possibility the wires are surface because there is a problem with the wall. For example services already in the wall like gas or water. Or just very pour plaster I have had huge lumps fall off and had to try and patch it as plaster would not touch it says whole wall needed redoing which would go way over budget.
ericmark

Postby kuzz » Thu Feb 28, 2008 10:55 pm

are the walls & ceilings concrete? if they are you've got some serious hard work on your hands to chop them in
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Postby jcwalker » Fri Feb 29, 2008 4:34 pm

The walls are plastered (definitely no concrete). I've drilled holes for various fittings on these walls and it wasn't a problem going in about one and a half inches, maybe two.
Also, definitely no water pipes or anything in the way, they all go along bottoms of walls.
So, the tools that cut out two grooves (re: ericmark), are these power tools or manual?
Also, the issue of having the wires protected by trunking inside the wall - is this purely to protect from someone drilling into them, or is it just because they need some space around them? If the latter, I could just use the plastic trunking I already have (which is rectangular in shape so should sit well in the grooves).
Thanks all
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Postby kbrownie » Sat Mar 01, 2008 7:17 am

Hi jcwalker,
if you follow the permitted areas vertical/horizontal explained earlier, you can just chase and clip cables without using protection. But i would not fault you for running it in conduit.
The tools which have been mentioned are called wall chasers (electric), i've seen some at aldi for about £35 I have used one, ok on breeze block and small DIY jobs. The pro- ones are quite a tasty price. You can also get an attachment for SDS Hammer Drill that chases out too. But I have not used a good one yet.
Alternative: Mark out on wall your cuts, steady hand with small/mini angle grinder (£15-20) cut both edges of chase and then chisel out.
Good Look, stay safe and safely isolate any circuits you work on.
KB
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Postby ericmark » Sat Mar 01, 2008 12:52 pm

As to using plastic trunking yes I would. Think my son got electric grove chaser from screw fix and SDS drill with rotor stop to chisel with from B & Q that works very well but a bit on heavy side. The unit to cut square holes I think Screwfix OK for loads of houses but tend to use SDS drill with chisel myself. The hammer drill that chases out I agree with KB not found a good one may be because although my drill has rotor stop it does not have rotor lock and they don't seem to want to stay flat on the wall. Careful with finishing plaster I have had a few bags that were off, date still OK but went off very quick and if you haven't used before you tend to think its your lack of expertise not bad plaster. The polyfiller stuff shrinks too much with deep groves. But takes some expeareance to know how long to leave before coming back to finish with float and water. And of course with so much water power must be off. The trunking, caping, conduit or what ever you use is really to stop the plaster from damaging the cable when using float etc.
ericmark

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