Running cables through a cavity

D

DNS1

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Just seen someone mention on another thread that running cables in a cavity is bad practice.

Can anyone elaborate for me, I was under the impression that this was ok but not ideal in a new build etc.

How should it be done these days? I'm in a 1990s flat and just wondering how a rewire will be possible without completely trashing ALL the plasterboard!
 
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I believe it's the practice of running cables up/through an external cavity wall, i.e, from an external meter cabinet upward to an internal DB, that is frowned upon as you are bridging the moisture gap.

Also there is no support offered to the cables and they could be subject to damage that you wouldn't be aware of.
 
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Agree. Most new builds have cavity walls anyway, When it comes to rewiring we wont be doing it in trunking. Fishing cables down the walls everytime for me, Aslong as its within the zones but i would never run cables down a cavity between the internal and external skin of the building.
 
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Lenny said:
I believe it's the practice of running cables up/through an external cavity wall, i.e, from an external meter cabinet upward to an internal DB, that is frowned upon as you are bridging the moisture gap.

Also there is no support offered to the cables and they could be subject to damage that you wouldn't be aware of.
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sorry to change subject alittle but,as u say lenny bridging moisture gap, how does that relate to the pump in type cavity wall insulation. had mine done 2yrs ago now seem to have a lot of damp. any advice anyone?
 
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Is your wall stone or brick type construction?
I have heard that if its of stone type then injecting insulation can create damp spots in the future.
 
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goldie said:
Agree. Most new builds have cavity walls anyway, When it comes to rewiring we wont be doing it in trunking. Fishing cables down the walls everytime for me, Aslong as its within the zones but i would never run cables down a cavity between the internal and external skin of the building.
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Used to be done though, seen a few wired from new like that, all circuits run down the cavities and then through to points. Terrible really, all that cable just hanging on concrete block edges....great holes through to the cavity. Not the way to do it but would struggle to justify that with a reg. common sense over rules!
 
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Ok lads, but how is it to be done on a new build now?? I can be sure of it that all the domestic installers out there aren't carrying 25mm Galv, bushes, end boxes, etc!

So how are they doing it!?!
 
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Chop out, or run within the internal cavities, also make use of loft space and under dwelling space. If its solid ceiling and solid floor you can do on surface using decorative coving trunking from above or channel out the floor.
 
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Chase out the wall in the correct zones....
Metal boxes, grommets and oval conduit........
Cables in external cavities does not comply with building regs, is bad practice as previously stated due to lack of support and subject to damage.
Do people not get taught this in apprenticeships?????
 
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If the cables are run within the plaster you'll need rcd protection, you will never cut in 50mm in standard breeze block because you'll be breaking a reg from part A of the building regs.... Structure I think it is, Also I'm a Jib Approved spark thank you very much!
 
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cdavies33 said:
Are you kidding me?!?! Tails to the consumer unit we are talking about here!
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Yes your method is correct for tails.
I should really start reading all the posts first. Lol
I was just referring to standard installation.
And yes straight through is fine.
I think you will find that the majority of domestic installs don't comply from what I have seen
 
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rich.250 said:
Yes your method is correct for tails.
I should really start reading all the posts first. Lol
I was just referring to standard installation.
And yes straight through is fine.
I think you will find that the majority of domestic installs don't comply from what I have seen
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I agree, I bet 99% of contractors out there just run them up the cavity and just keep it hush hush and I have no shame in staying I done and still do it this way. But if anyone does have another method bar the galv conduit route, be sure to let me know!
 
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I've seen a lot of that. I always try to make a rewireable system using oval conduit to roof/floor void, this means cables can be replaced wit no disturbance of decoration.
Better practice I think, and quicker than clipping loads of cables
 
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cdavies33 said:
I agree, I bet 99% of contractors out there just run them up the cavity and just keep it hush hush and I have no shame in staying I done and still do it this way. But if anyone does have another method bar the galv conduit route, be sure to let me know!
Click to expand...

I suppose you could fuse down in meter box and run earth metallic sheathed cable to distribution board lol
 
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mackers said:
sorry to change subject alittle but,as u say lenny bridging moisture gap, how does that relate to the pump in type cavity wall insulation. had mine done 2yrs ago now seem to have a lot of damp. any advice anyone?
Click to expand...

Some of the older insulation was of a porous type so that when the driving rain soaked through the outer wall it wicked through to the inner wall causing damp. The new stuff is supposed to be a silicone based product, I don't believe and will never get this pump in stuff done.
A mate of mine how is a builder, has partially pulled down a pumped insulated wall in prep for an extension, the black mould damp was unbelievable.
I truly believe in insulation whilst a new build as an air space cavity still remains.

Back to running tails through the cavity, I usually use a but of 40mm waste pipe, that can be sealed into place and a little bit of intumescent pillow in the pipe sorts the fire barrier.
 
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If were talking about meter tails here, then sorry but it's stright through the cavity for me every time!! I'm aware it's probibly against building regs, but until I see problems with it for myself, i'm carrying on like that!
 
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DNS1 said:
Is the capping really necessary?

I've always been under the impression that for a new build the cables are normally just clipped direct to the breeze block before the dot and dabbing...
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capping is to stop the plasterers trowel, and thats it! Thats why you get plastic capping! So if it's being dot & dabbed then it is not necessary and a waste of time. But nowt to stop you doing it and making it look really pretty .....
 
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Slightly off-topic I know. But kind of on the same subject.
It hasn't happened yet but I'm sure sometime soon I'll have to 4" core drill through a wall with blown in insulation for a kitchen extractor.!
What happens to the insulation ?
 
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rich.250 said:
Do people not get taught this in apprenticeships?????
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What apprenticeships, didn't they cease to exist years ago to be replaced with the quick course

GT1 said:
Slightly off-topic I know. But kind of on the same subject.
It hasn't happened yet but I'm sure sometime soon I'll have to 4" core drill through a wall with blown in insulation for a kitchen extractor.!
What happens to the insulation ?
Click to expand...

Depends on the insulation used, blown wool usually stays in place to some degree long enough to get a sleeve in the worst stuff I have found is the polystyrene chips I usually drill some small holes around the diameter of the core bit and inject some foam before using the core drill, the foam will retain the poly chips in the wall and cut down the mess
 
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