Cables run in Cavity Walls

Discuss Cables run in Cavity Walls in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Rodnay

Think it was done alot in
the past, come across a few, to be honest my heart sinks when I find it, cables chucked down from loft to ground floor, no support in the way of clips except the rough edge of the concrete block its draped over in the loft. Dirty great holes bashed from cavity to K/O box.


Bad bad bad

Would never do it!
 
Last edited by a moderator:
SPARTYKUS said:
Rodnay

Think it was done alot in
the past, come across a few, to be honest my heart sinks when I find it, cables chucked down from loft to ground floor, no support in the way of clips except the rough edge of the concrete block its draped over in the loft. Dirty great holes bashed from cavity to K/O box.


Bad bad bad

Would never do it!
Click to expand...

Is this practice still permitted?

I don't think it is, but stand to be corrected.
 
You'll need to make sure you consider the reference methods 100, 101, 102 and 103 and consider their impact on a conductors current-carrying capacity as illustrated in Table 4D5 in Appendix 4.
 
I'd never run a cable in a wall cavity, it's just bad practice. Only exception for me would be going through
a cavity, e.g. outside light feed. If you do decide to do it, which I urge you not to, then I'd use something beefier than T&E too.
 
Considered a bad practice these days, for several reasons;

a). the cable could get damaged by sharp edges etc within the cavity when pulling in.

b). the cavity could be filled with polystyrene insulation, which reacts with pvc

c). and most importantly, the cable can rest against the inner wall and the outer wall,
and therefore becomes a 'bridge' for moisture to run from the outer skin to the
inside skin, and thereby creating a damp patch on the inside of the wall.

This negates the whole purpose of having a cavity, hence you will find that building
inspectors on extensions and new builds will insist on having any cables they see
in a cavity removed and re-run . Short answer is, don't do it !
 
Last edited by a moderator:
the oracle said:
b). the cavity could be filled with polystyrene insulation, which reacts with pvc
Click to expand...
Slightly off-topic but you try tell that to static caravan manufacture's.....alot of modern caravans, most notibly Willbery have all the walls filled with polystyrene.....and the twin and earth literally just hidden in the middle of it.

Been to loads of caravans where people want single-sockets making into doubles.....chop out the other half with a stanley haha....and its completley chocker with polystyrene. Seriouslly no idea how they get away with such crap.

Came across one earlier with plug in light switches haha it made me laugh.....wired from the CU down to the switch....then they have chockyblocks with inbuilt plug-in-jobbys? Really not sure what they're called because hardly ever come across them but you'll probably no what i mean.....then they have the light switch wired and plugged-in in the drylining box. They're reasoning.................when the light switches become faulty (and by that wording they're obviouslly expecting them too) they send out a maintenance team, and because they're not qualified electricians they're only allowed to plug in equipment....thats the reason for them having their light switches and sockets wired in a plug-in system.

Lazy.
 
cavity waal insulation does not react with the pvc of cables any more.
 
phil d said:
maybe not,but at leastI know why women develop damp patches now,and there was me thinking it was the effect I had on them lol.
Click to expand...

c). and most importantly, the cable can rest against the inner wall and the outer wall,
and therefore becomes a 'bridge' for moisture to run from the outer skin to the
inside skin, and thereby creating a damp patch on the inside of the wall.
Click to expand...

You talking about this??

This is just another old wives tale, You could say the same about the metal ties the brickies use or the insulation materials that fills the void. The only time your going to get damp between walls, is when the outer wall (or small area of it) is no longer watertight, eg ...unfilled holes, pointing failure etc!!


​
 
Engineer54 said:
You talking about this??

This is just another old wives tale, You could say the same about the metal ties the brickies use or the insulation materials that fills the void. The only time your going to get damp between walls, is when the outer wall (or small area of it) is no longer watertight, eg ...unfilled holes, pointing failure etc!!


​
Click to expand...

not true, wall ties have little zig zags on them so the water drips off in the middle of the cavity. it is a fact that things bridging the cavity can cause damp problems, i've seen it enough times. even on a new build where the brickies had not cleaned the snots off the ties, damp was coming right through as the outer wall was not rendered yet. and as for cavity wall insulation that fills the cavity, that certainly causes damp problems and theres loads on the internet about it.
 
ExArmy said:
not true, wall ties have little zig zags on them so the water drips off in the middle of the cavity. it is a fact that things bridging the cavity can cause damp problems, i've seen it enough times. even on a new build where the brickies had not cleaned the snots off the ties, damp was coming right through as the outer wall was not rendered yet. and as for cavity wall insulation that fills the cavity, that certainly causes damp problems and theres loads on the internet about it.
Click to expand...

Agree with the 1st bit.
My house is early 1900s, two brick leafs, mortar filling the tiny gap between them, but the house isn't riddled with damp.
The little building technology I know..., it's more to do with the breathability of the walls and not having running water flowing down the walls.
 
That may be your opinion, BUT, that is what the current teaching is, and has been, for the last 8 years that I know of. It is laid out in the syllabus for the C & G 2330 course, and will be in the C & G 2365. And, as I said, Building Inspectors will pull electricians up on it, so I think it is wise to discourage it, rather than risk the wrath of an angry Inspector ! Don't you?
 
ok time to put my hands up! cavity wall fed from upstairs bedroom under floor boards going down to socket in added conservatory. i rewired this and thought just take cables where they had been before as only about a metre if that down to internal consevatory, am i a bad person?
 
oh yeah front room was running in external wall so checked original cable was ok,left in place and connected to new wirring using mf box under upstairs floor boards.ok?
 
Considering what you could have done this, I would say, is not a problem, if you can avoid it then yes do not run cables in the cavity, but also be realistic about installation.
Just don't use it for your assessment!:angel_smile:
 
NICEIC Snags book (so it must be right :) )quotes Regs:
522.5.3, 522.8.1, 522.8.4, 522.9.1, 522.10.1 and 523.7

for not doing it. Apparently NHBC requirements, section 8.1 S2 also says it is foreboden apart from with meter tails. Considered bad practice as others have said.
 
ExArmy said:
only thing i'd run in the cavity is tails when doing board changes and there are only 16mm tails.
Click to expand...

16 mm tails are more than likely fine in the majority of properties in the uk.
As for cables bridging the cavity causing damp problems ive seen it first hand!! In and older property.
I would Never run a cable in a cavity!!
 
ExArmy said:
not true, wall ties have little zig zags on them so the water drips off in the middle of the cavity. it is a fact that things bridging the cavity can cause damp problems, i've seen it enough times. even on a new build where the brickies had not cleaned the snots off the ties, damp was coming right through as the outer wall was not rendered yet. and as for cavity wall insulation that fills the cavity, that certainly causes damp problems and theres loads on the internet about it.
Click to expand...

They might have now but they didn't before, they used to be solid affairs. So what are you saying that the outer brick skin is going to be sodden with water, ...Not on your Nelly, the only time water is going to enter cavity space above a damp proof membrane is when there is unsealed openings in the outer skin or if the wall needs re-pointing.

All this cables run in cavities causes damp in the house is just absolute rubbish. Not good practice it maybe, but for other good reasons ...not because they cause damp!!
 
Engineer54 said:
They might have now but they didn't before, they used to be solid affairs. So what are you saying that the outer brick skin is going to be sodden with water, ...Not on your Nelly, the only time water is going to enter cavity space above a damp proof membrane is when there is unsealed openings in the outer skin or if the wall needs re-pointing.

All this cables run in cavities causes damp in the house is just absolute rubbish. Not good practice it maybe, but for other good reasons ...not because they cause damp!!
Click to expand...

condensation forms in the inside of the outer leaf, this will then drip down to the bottom, if there's something bridging the cavity then it will move across to the inner leaf. also driving rain can penetrate small cracks in the render or pointing, which will cause the outer leaf to get wet and again moisture will drip down the inside of the cavity and if it comes across something bridging the cavity then it will move across. now in an ideal world the outer leaf would be completely watertight, but over time problems can develop with guttering, fascias, pointing, flashings, render etc, and in those cases water gets in, now if the cavity is clear then it will just drip down to the bottom where it will do no harm, but if it can get across the cavity then it will and start soaking the inner leaf.
Ive seen things bridging the cavity enough times to know what i'm talking about, no amount of people on a forum telling me it's an old wives tale or to "get real lol" is going to change my mind. if you think you can just do anything you like to a cavity and then if you end up with damp problems then it'll be down to the outer leaf letting water in and in no way related to whatever there is now bridging the cavity( be it insulation, cables, pipes etc) then you need to ask yourself why cavity walls were invented in the first place, and had the "thing" bridging the cavity been there then would damp be able to get accross?
im not saying anything crossing a cavity will cause damp, if i have to drill through a cavity then I drill from the outside at an upwards angle (about 30 degrees) that way if any moisture were to get on the cable then it would just drip off as it can't travel uphill.
 
The only thing that I can add to this debate is that back in all the storms we had a few months ago, I had an RCD trip out in my own house.... what was happening is that a 10mm shower cable fed via the cavity (before my time) was acting as a very nice runway for water getting in somewhere (hopefully now sealed up!), and that water was travelling straight into the DB.

But, I got into a bit of a scrap with an elecsa assessor a few years ago when he demanded that a short (<1m) length of tails that I had buried in the wall from old position to new get redone to a proveable >50mm depth (had installed them at about 30mm and put some steel plate in front). I pointed out that there wouldn't be an awful lot of wall left given the dia of the tails and he said just to run them in the cavity instead. I disagreed due to insulation and we ended up compromising by me using a thicker plate in front.
 
ExArmy said:
condensation forms in the inside of the outer leaf, this will then drip down to the bottom, if there's something bridging the cavity then it will move across to the inner leaf. also driving rain can penetrate small cracks in the render or pointing, which will cause the outer leaf to get wet and again moisture will drip down the inside of the cavity and if it comes across something bridging the cavity then it will move across. now in an ideal world the outer leaf would be completely watertight, but over time problems can develop with guttering, fascias, pointing, flashings, render etc, and in those cases water gets in, now if the cavity is clear then it will just drip down to the bottom where it will do no harm, but if it can get across the cavity then it will and start soaking the inner leaf.
Ive seen things bridging the cavity enough times to know what i'm talking about, no amount of people on a forum telling me it's an old wives tale or to "get real lol" is going to change my mind. if you think you can just do anything you like to a cavity and then if you end up with damp problems then it'll be down to the outer leaf letting water in and in no way related to whatever there is now bridging the cavity( be it insulation, cables, pipes etc) then you need to ask yourself why cavity walls were invented in the first place, and had the "thing" bridging the cavity been there then would damp be able to get accross?
im not saying anything crossing a cavity will cause damp, if i have to drill through a cavity then I drill from the outside at an upwards angle (about 30 degrees) that way if any moisture were to get on the cable then it would just drip off as it can't travel uphill.
Click to expand...

We'll agree to differ then, because i am Adamant in what i have posted too!! By the way, there shouldn't be any condensation within the cavity area, ...if there is then something else is wrong, and it's nothing to do with any bridging being present.

One more thing, i don't think i've ever seen a cavity between the two courses of bricks/blocks being completely clear/clean, or should i say, that haven't numerous counts of fallen mortar trapped by ties etc, bridging the cavity. No sign of damp on the inner walls anywhere..
 
Has anyone mentioned 120 year old miners cottages with metre thick walls?

No cavity here!!!

Maybe should have stuck with them what withh all the arguements cavity walls are causing!!!
 
SPARTYKUS said:
Has anyone mentioned 120 year old miners cottages with metre thick walls?

No cavity here!!!

Maybe should have stuck with them what withh all the arguements cavity walls are causing!!!
Click to expand...

I used to live (a long time ago) in a GradeII C13th (parts > Victorian) old hostelry / pub. One of the INTERNAL walls was 18' (and it was just wall, no hidy holes) and the exterior walls were built castle style - thick outer, thick inner and the 'cavity' filled with rocks and rubble. Over the centuries it had sunk about 1m into the ground, no dpc there!!!
 
should i just admit this before hand and say the job was a nightmare,should i put it on eic as another problem that could be addressed?
the property is my sisters so i could always correct at a later date if elecsa had a problem with it.
i got to admit this property was never the ideal property i wanted to use as for registration but the only one i had the opertunity to use.i did a partial rewire as not to chase walls to lighting switches but connect above either via light fixings or mf boxes. didn't expect to have to put in tt spike as never done it before,never expected kitche lights and sockets to be fed under lintel in kitchen extention touching plasterboard ceiling.
 
If this is your job for assessment then I think you are panicking waaaaaaay tooooo much. If you are going for a DI, the assessor is going to slap the sticker on your back. The scheme want your money. I really don't think the assessor will pay that much attention mate. You could put on the certificate that its wired through peanut husk and I doubt the assessor will notice (installation method R118 by the way). You just need to show a tidy job, an ounce of intelligence, a stash of cash and convince him that you won't kill yourself or the customwer. And then 'Jobs-a-good-n' :)
 
SPARTYKUS said:
Has anyone mentioned 120 year old miners cottages with metre thick walls?


No cavity here!!!


Maybe should have stuck with them what withh all the arguements cavity walls are causing!!!
Click to expand...




The reason these walls were so good was due to the porosity and continual cycle of absorption and evaporation coupled with the width. Most cavity walls with a cavity wall not only depend on the level of absorption of the brickwork but also the level of workmanship.
Cavity walls are so designed that even if the outer leaf was saturated, the inner leaf should remain dry. This is achieved by drip features on wall ties and a separation between leafs preventing capillary action of water.
If a wall is correctly constructed then I personally, would suggest that the mere fact of a cable touching both leaves could not lead to damp, as the cable is not porous, however if the pointing is poor then there is a chance of running water down the inner face of the outer leaf, which could run across to the inner leaf and cause damp.


Interstitial condensation is a very real damp causing problem particularly in walls in new timber houses with no vapour barrier, but thats another issue.
 

Reply to Cables run in Cavity Walls in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Similar Threads

S
EV charger cable in wall cavity
I would like to hide the cable to an EV charger. The consumer unit, meter cabinet and charger would all be on the same wall. About 5 metres from...
Replies
19
Views
2K
DPG
DPG
D
External cable run best method for this situation
Hi I've got an new outbuilding that needs power run out to it, the building is very close to the house and the original plan was to run an...
Replies
9
Views
1K
OnlQQker
OnlQQker
Cjm1992
Cables within stud walls
Hi All, Wondering if I can get some advice. Basically I’m having exposed joist ceilings in my house and I’m in the process of slowly changing all...
Replies
5
Views
1K
Cjm1992
Cjm1992
C
Moving cables and sockets/switches over insulation
Hi, I'm about to reroute cables and sockets/switches from the ceiling down to the socket height after insulating a wall. I understand this will...
    • Like
Replies
2
Views
199
Rockingit
Rockingit
B
How do I attach switch back box in lathe and plaster wall
I'm installing smart modules in my light switches which means I need to replace the existing 25mm back boxes with 47mm ones. Downstairs all walls...
Replies
0
Views
346
billyb_1234
B

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

Tags

advice aus cable circuit course earth electric electrical electrician hello led light lighting lights looking new please question rcd socket supply switch testing training wiring
This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock