CAN ELECTRICIANS INSTALL CABLES IN A CAVITY WALL?

[@efixx]

This question was raised following an eFIXX video review of the Hamilton Elemento outdoor sockets. Check out the review 📺 👉 kzbin.info/www/bejne/i6C3ZXtrmJyohMk

[@christastic100]

Interesting subject There are several points I would like to make on this subject. First of all I have never ever seen a twin and earth cable other than very long inappropriately installed as overheads damaged by its own weight in thirty years in the trade ever . Saying that I would always fix cables where they can be and always on new insulations with fire clips as required. Second I have pulled redundant cables out of cavities that have cavity insulation and other than slight discolouration to the surface sometimes as dots the cable looked and felt like new Thirdly the insulation usually acts like a rudimentary support for short retrospective installed runs . Fourth . I don’t think anyone would resort to this practice in an ideal world but sometimes it’s the only practicable option for shorter runs . Finally regards breaching the damp barrier I would suggest a slight misunderstanding of the rules intention to not breach the gap with damp conducting materials otherwise you couldn’t put cavity insulation in . Most trades seal around the holes they make .

[@mrclive5]

Ran about two metres of 2.5 T&E down a cavity in the last month, quite proud of the achievement. It's fully sleeved end to end in flexible conduit, so well protected. There were few options open to me, it's a basement conversion with membranes everywhere, couldn't peirce those, so down the cavity it went. My deceased business partner did a few years for the council and dropping cables down cavities was the preferred method.

[@johnavery15]

What are the alternatives for outside lights or an outside socket - conduit down from a soffit or SWA up from the ground? Both seem overkill and the easiest, safest, cheapest way is through the cavity surely?

[@jamiebourne8047]

100% agreed, any other way you'll never get the job.

[@jameshansing5396]

Yeah just lash it in….. 😂

[@scott1506]

exactly mate its totally dumb. they would just get the next electrician .

[@jacobedmonds305]

As with other comments. I’m interested to know about running cable across the cavity for outside lights and sockets etc. Also really interested to know what we’re supposed to do with metre tails… every domestic install I’ve ever worked on, the metre tails come through and up the cavity to the CU. Great video as always though. Interesting to see what the regs say.

[@seankearney6915]

Yes me too that was my thought exactly the minute he said the words "bridging the cavity" My house has a double socket on the wall then below it a fused spur to an outside RCD socket. So it must be bridging the gap. The main socket is channelled in the wall as I could see the different coloured plaster when I decorated.

[@treborriam]

Not on my jobs they don't

[@jacobedmonds305]

@@treborriam what do you do then?

[@treborriam]

@@jacobedmonds305 it depends on the situation so it's hard to erd to give an answer.

[@ayeroxor]

@@treborriam then give one example?

[@brianpiddock6074]

This Is a crazy one, Plumbers always put Gas pipes through walls . I've always put a bit of conduit or oval trunking between fittings never had a problem up to now.

[@treborriam]

That's acceptable and correct

[@Poorlybobsdad]

Me too, I up-rate the conductors to 4mm to compensate for the insulation (32a ring) and fix it to the inner skin to stop moisture transfer.

[@mikeselectricstuff]

Hard to see how contact with a small area of non-moving polystyrene will cause significant damage - there's only a finite amount of chemical there to react. IMO the sole issue is de-rating the cable as appropriate to take into account the effect of the thermal insulation ( including the possibility that insulation may be added later if not there already). Possibly the only other thing to bear in mind is that cavity insulation is sometimes added by drilling holes from outside, so perhaps worth leaving a notice on the CU of the location of any cavity runs.

[@Rosscoff2000]

I've seen pictures cables almost melted through from contact with polystyrene over a few years in a warm loft. Something in the polystyrene seems to slowly dissolve over.

[@carlf6507]

So how can the DNO run meter tails up a cavity if you’re not supposed to use it? How do you get power from inside to outside if you can’t bridge the gap? Seems to me that someone at building regs hasn’t thought this guidance through as that’s nigh on every property in the U.K. going against the regulations.

[@electricalstuff259]

Was about to post about the inside to outside point. Surely we shouldn't be able to drill a hole through to fit an outside light etc in this case?

[@carlf6507]

@N. J. Farrar Property Maintenance but you’d be bridging the gap which they say is a problem in this video? I’ve done plenty of outside socket and light installs. Yet this infers that me running a cable through the conduit (with the conduit bridging the gap creating a moisture issue) is against building regulations. It also doesn’t explain how the DNO can run meter tails up the cavity. I’ve yet to see a set of meter tails in conduit. They are just fed up the cavity to the board from what I’ve seen.

[@efixx]

Interesting points brought up here. Even brick ties have a little dip half way along to allow water to drip off them. I guess if the cable runs slightly downwards as it leaves the building it would prevent moisture transfer. Further investigation to follow.

[@electricalstuff259]

@@efixx I mean we all do it, have to get power outside somehow but imo these regs are perfectly clear - you're not allowed to do it. Angled holes are good to stop water ingress but won't do anything to prevent moisture wicking.

[@davideyres955]

It seems to me that bridging the cavity from inside to outside is ok (or are we saying you live with what you’ve got and the regs say you can’t have any new connections outside of the house) Although I have not read the text I would guess it means running the cable in parallel inside the cavity not at right angles through the cavity. Reading it that way it makes sense, but just saying you can’t breach the cavity is unworkable.

[@peterdifolco313]

I’ve come across cables run vertically in cavities many times , yes there maybe some disagreements whether this is a bad thing but it prevents people accidentally drilling or nailing though a cable .

[@HeathenGeek]

i ws surprised to hear 'No' at the end of that. My takeaway was 'Yes, but with certain considerations'. So. . . 'Yes'.

[@steveosshenanigans]

It’s a common practice in Australia when running cables between power points or outside lights

[@ragemachine4991]

Common sense will suffice in every case whether it be cables, pipes or anything else passing through a cavity, the fact is building design has always presented problems for services and cost will always be a consideration, whatever the method of installation it doesn't necessarily mean it's not acceptable? if the the building regs were that critical we wouldn't have running water, flushing toilets and drains passing through walls?

[@nocode1603]

Yeah I remember we used to drill a hole in to the cavity then try fish out a string with a weight for some outside lighting jobs I think if your only going down a few hundred mm for a pir as long as its not ramd full of glass wool or polystyrene beeds filling the cavity with insulation was the worst thing to help transfer damp between the brick skins...👍

[@Daniells1982]

The building regs are clearly referring to vertical runs through the cavity, not horizontal runs to outside accessories. Do people still actually run cables vertically through the cavity these days? It's not something I've done since starting my apprenticeship in '98, although have seen properties wired like that. Thought it was old hat and people stopped doing it for the reasons Joe mentioned, plus the fact the building regs clearly state not to which is legislation.

[@efixx]

It's interesting the amount of engagement the video's had, it could be an indicator people are doing it again?

[@ady8077]

If the building regs only allow for what you quoted, then we shouldn't even run tails through, or drill out from inside for any electrical accessory ?

[@efixx]

It's an interesting point isn't it? Further investigation to follow, I think as long as you go straight out or maybe slope the hole downwards as you go out the building it could be ok.

[@chrisf1600]

I just discovered that whoever built my 1950s home used this trick. There's a spur coming off the upstairs sockets circuit that vanishes through a hole in the first floor wall, runs vertically inside the cavity for about ten foot, and then re-emerges in the room downstairs. I was a bit surprised when I first saw this but apparently it used to be quite common. I'm planning to replace the cable because it must be 70 years old by now, and the insulation has started to crumble.

[@guywren4801]

Even more opportunities for sanctimonious pedantry "A porch light ma'am? - No problem - but you won't believe how much cable we'll be using, how much we'll charge and how ugly it will be when run down the outside from the soffit of your otherwise lovely looking town house" "Only a cowboy would bridge that 100mm cavity" "We have the regs on our side" Wouldn't it be better for the electrician industry to look at how best to solve the cavity bridging requirement for outside sockets and lights or don't they have a seat at the table when the building regs are decided?

[@muzikman2008]

I get not running meter tails for more than 3 meters to inside, as it is hard to trace where they are, but i dont think a 300mm horizontal bit of cable to an outside light/socket is gonna be a problem. I also agree with the PVC reacting with polystyrene insulation is a problem with the chemical reaction. i suppose if its in a metal conduit or trinking its gonna be fine. dunno... 🙄

[@ravi5602]

Was speaking to a technical advisor from my local DNO in Dec 21 and I was surprised to find he had no issue with meter tails being run inside a cavity. I have to run some to a relocated meter box and the only realistic route id via the cavity in some conduit (a..k.a waste pipe)...

[@efixx]

The DNO doesn’t have responsibility for the tails - you do - check that derating if the cavity is full of thermal insulation

[@sbwende]

In Denmark it is very normal practice to run cables in the cavity. The inner leaf is built first after which the cabling is run including clipping after which the outer leaf together with the cavity wall insulation is built.

[@glenwoofit]

So every time you run a cable through a cavity to a socket or outside lights you are going against building regs by bridging the cavity. Well that's every property in the UK then.

[@davidreynolds9649]

Indeed, including telephone cables! @RubberThingy I think you are right but I am still disappointed that the subject wasn't covered. After all running across a cavity is very similar to running in a cavity! I think I am right in saying that gas and/or water regs require all pipes to be sleeved when passing through a cavity.

[@efixx]

Interesting points in this thread, I think the gas pipe being sleeved is also about preventing the cavity filling up with gas in the event of a leak. It's an interesting point about going through a wall to a socket or light. Further investigation to follow! Also I had a boss once who'd knocked a corner of his window out to run a cable outside!

[@jimporter]

Wonder if anyone has told satellite, cable and broadband installer this?

[@seankearney6915]

@@efixx I would have thought it more to do with the lime in the mortar. I have seen them sleeve it in thick yellow tape, which wouldn't stop a leak. Also how are you going to break the copper in the cavity without piercing the sheath first. I would hope no fitter actually embeds a soldered or compression joint in the cavity.

[@Mike-jj2qf]

Can be ideal for running SELV cables to feed something like a ring door bell or exterior mounted cameras for example, when surface containment would be unsightly or isn’t an option.

[@richardprice4954]

A now the government is going green and a lot of social housing is being covered with polystyrene blocks before rendering, is it ok to clip lighting cables or external socket outlets being fixed to the face of the house beneath the polystyrene if it’s clipped in zones and protected by an rcd?

[@tonysheerness2427]

Even if conduit is used inside the cavity it will transfer moisture from the outside to the inside, and if vertical the weight of the cable is still a problem. The shorter the run of cable the better, better to go through the cavity than a long run of cable.

[@kevrus01]

No mention of boiler flues or extraction fan ducting, both of which will bridge the cavity between inner and outer leaves

[@MarkJT1000]

About 40 years ago Norweb, our local electricity board at the time, installed an electric shower and ran the heavy duty cable down from the 1st floor bathroom right down to an air brick opening in the sub-floor void below. Seemed to me like a good idea at the time. No channelling out or disturbance of decoration etc.

[@scottsparky1]

It's always been done that way for a long time. That's how the cables are run in my house. All cables come from above down the cavity into the cupboard where the consumer unit is.

[@enigmaticx326]

I live in an older place which was renovated about 20 years ago and some knob has not only run cables through the cavity walls but also installed junction boxes there too. I’m not a sparky - but that just doesn’t feel right to me.

[@Leodis.Leather]

Sky engineers drill straight through the wall and poke the cable through then run it up to the dish, I know that’s not carrying current but I do always wonder about whether it can cause damp issues?

[@_______DR_______]

They usually fit a cover plate, blast the hole with silicone, leave a drip loop on the cable. Not really likely to cause any trouble.

[@abdulseaforth6930]

Hmm…. The transference of moisture between the cable (or conduit) making contact between the inner and outer walls which can give rise to damp, is a problem in the making. Never gave it a thought until you mentioned it.

[@Dog-whisperer7494]

If installing outside sockets and switches I would use SWA surface mounted on the outside or if I have to go through the wall I will pass a cut to length pease of 22mm galvanised conduit through fixed to the back of the back box and then pass the cables through the conduit. So do I now have to rethink ? . Interesting one great video as always joe 👍👍👍❤️

[@iantibbetts6871]

There's a few YT sparks showing off their angle drilling prowess, through cavity walls to get the ev car charger supply from the CU. Hmmm

[@andjc72]

I doubt the occasional odd few metres of electrical cable inside a brick cavity will ever make much difference to the air flow or damp being transmitted via the cable, builders leave more than enough crap in them. In over 40 years iv'e never come across any problems with degradation of a cable touching any kind of wall insulation or over heating, one would expect the electrician to take into account cable calcs if it was a high current using circuit. many years ago local Authorities allowed rewires to be carried inside the cavity, I don't think this was good practice however to my knowledge there doesn't appear to be any lasting negative issues with these installation, street lighting columns often have several metres hanging through the middle with out to many faults, 90% of all conservatories have the socket circuit wired though the lower wall to each outlet, as for installing Micc into a brick cavity good luck with that, and wouldn't that transmit damp the same as any cable, plus Micc is not that great of cable as after 25 years or so the terminations brake down and never seen a standard domestic house wired in the stuff.

[@davidreynolds9649]

Knowing my luck I (or the BT man) will drill through them shortly after install!

[@andjc72]

@@davidreynolds9649 LOL, this could happen but with a little fore thought and skill these issues can be overcome. Carry on sparking .

[@efixx]

All good points. 👍

[@treborriam]

You also need to consider that rodents will and do live in cavaties and love eating electrical cable

[@lukesmith8792]

Sometimes this is the only way, couple of tips I think it's important if you gotta do it, drill the holes at a angle so that rain can't run into and down the hole, and then after the cables in, blow out dust from holes then silicone both holes inside and out. And sometimes if I feel it safe to do so I try to leave some slack in the wall for the future me. A side note if there's only one cable being put into a terminal that holds cables with a skrew... Please please please double the cable up, it doesn't take long and isn't hard but it's something I rarely see done

[@GregMoseley]

So would dropping a cable down from a loft to the ground floor enclosed in flexicon be acceptable if the holes are then filled back in, this would prevent any exposure of the cable to the air and also prevent any moisture from entering

[@brianhewitt8618]

still wont be clipped, the more material you put around the cable will de-rate it further, you may create condensation in the tube which will follow gravity and of course it still has the ability to breach the leaves

[@alphamegansw]

Brick ties ( wall separators etc ) will cause moisture issues ( our buildings can weaken and spread without them) . It also prevents ingress and shocks to children etc ( they spill stuff and break external bits ) .always,try to use under building feeds via cavities ( the other trades appreciate it as well) . Not to mention it is a better use of space ( in certain centres I use flexible metal conduit similar to liquitite etc. tidier work with less chance of ingress or user damage .

[@maffysdad]

Haha, This is a trick question because how else are you to get electric cabling from the outside to the inside, regardless of if it's tails or twin&earth? Unless you have your own power station built within your property. So it's a physical impossibility. 1). Where I live the electric company have run their large tail cables up the cavity wall to my 2nd floor landing and into my meter box and four other meter boxes, all situated on outside walls (so the meters can be read). Then, and you can clearly see, the tails then go back into the cavity wall and up into the attic before feeding down into the fuse board. These properties were built in the 1990's. 2). Our new extension at my parents, still being built, has had an electrical feed taken from the current fuse box into a new fuse box spur, then the twin&earth taken up into the ceiling, ran through joists, then drilled out through the cavity wall into the roof space of the extension. Personally, for things I've done I've located the outside item where I need it, drilled a hole through to the inside, fed the cable through creating a drip point, sealed it, and ran the cable inside, in conduit. I personally am happy to see where cables are, but that drip point prevents damp, and the sealer stops the ingress.

[@MrWeddingPhotography]

I bet there’s millions of cables around the country going through cavity walls without a single overheating, fire, damp or cable damage issue.

[@efixx]

Oh well let’s just ignore best practice and crack on.

[@MrWeddingPhotography]

@@efixx but I wasn’t being funny, I was just stating the likelihood, meaning that IMHO, some best practice recommendations are questionable. You are the one who asked for our thoughts and opinions. If your that sensitive, don’t ask people to start a discussion.

[@MontyBurnsEsq]

@@MrWeddingPhotography Quite agree, no one can apply their own common sense to each scenario anymore. I don't really run down inside cavity often but if i do cables are always routed with the lowest entry/exit on the outside wall - water doesn't travel upwards

[@MrEggaz]

Seems a bit silly this one..

[@MrJoysiq]

In Australia we always do it

[@01dec2001]

Will this apply to DNO, s as well when they are running their mains to the meter cabinet?

[@joesouthgate]

They haven't run their main cable inside new build cavity for years and years. Look at any house built in the last 20 odd years and they nearly all have hockey stick entries to the bottom left of the outside meter box.

[@effervescence5664]

The specific passage quoted here is basically useless when not accompanied by things like Gas Regulations which allow you to bridge the cavity directly as long as the pipe is sleeved and sealed on the inner leaf. However your video title is about running in the cavity and not through it, theory being it's possible to run cables in the cavity without bridging it but only during construction but as more and more old buildings get polystyrene bead insulation and new builds are required to have either PIR/PUR or fiberglass wool insulation in the cavity why would anyone bother. If they're going through a cavity wall it's always better to just sleeve it with some pvc conduit, not even for the sake of protecting the cable but to stop the stupid beads flowing out the wall every time the outside lights get changed.

[@davepusey]

If the biggest issue is the risk of cable damage, then surely running SWA is the solution.

[@iansanderson4664]

Watched this with interest. Most of my house is solid walls, but some decades ago the kitchen extension was built with cavity walls and the contractor wired it through the cavity. None of that wiring goes through the outer leaf. This confirms my view that I was wise to resist salesmen who wanted to fill the cavity with insulation.

[@keithtaborkt]

At best good practice would be to use some high impact conduit through the wall as a sleeve

[@rogergregory5981]

Can't see any problem with going through cavity , common sense slop hole down to the outside seal hole and cable lays flat on wall, loop round to go up water runs off bottom of loop no problem no damp

[@garycon25]

No matter how politically correct a cable installation is, there is no certainty of zero risk, and any good experienced electrician who has spent the 80s and 90s safely re-wiring houses will stand by the safety and practicality of wall cavities as natural cable routes...

[@stevendouglas3860]

Well ...on my new build they run a swc through my cavity to my garage . My house was built in 1992 . 13th edition . Needs updating 🙄

[@carlosjackal7624]

4 inch of cable suspended in fresh air is no concern of mine.you can always run a bit of 20mil conduit through the hole first but we dont get 10 hour days do we.

[@efixx]

It's more about long unsupported runs in the cavity.

[@alphamegansw]

AlwYs prefer a it’s to walls straddled by ugly conduit/duct that is prove to weather /UV or morons with trolleys. I have yet to see someone drill into it( I have seen a logo guys drill into cabled joists and smashed conduit in garages etc … soyesafter 50 + years I would go for a a it’s every time

[@anthonysalisbury6945]

What is the correct method to cross the cavity.....to install an outside socket?

[@efixx]

Short length of conduit

[@mra813]

It s happening a lot. There is a chap on TikTok whose unique selling point is the hidden cables for his CCTV installs - quite often in the cavity. From the comments it is OK because it is extra low voltage 🙄.

[@efixx]

Unless the cavity is stuffed with polystyrene

[@mra813]

@@efixx there is still the issue of bridging the cavity, the voltage level is almost irrelevant

[@samstone1884]

So my question to that is how are we as electricians able to ever fit outside sockets or lights makes no sense at all

[@iansanderson4664]

A recent Artisan Electrics KZbin video shows drilling a hole for an EV charger causing little polystyrene balls to flow out of the hole.

[@anthonyminchinton3399]

Local Authorities and Housing Associations are still running cables in cavities when doing rewires because of cost, they want the cheapest job possible. Everything is short term because there is no money.

[@G1ZQCArtwork]

I said no from the start. (5 stars for me). Also remember, Rodents tend to travel around your property in the cavity. (Oh yes they do!). Cables are both a help and a hindrance to Rodents, Rats tend to chew them to get past. This can cause nuisance tripping, which will be hard to find. So NO don't do it.

[@merlin5476]

Speaking of rodents, i had a nuisance tripping issue a while ago where a mouse had bizarrely squeezed into a tsso, but managed to get passed the 2, 2.5t&e cables & the grommet then chewed the cables !!! Even paul Daniels couldn't have done that.

[@jmeiklejohn]

If they advise you to not run cables in the cavity, they need to come up with a new way to build houses. A lot of concrete floor new builds literally only allow for trunking/Conduit to which customers turn their nose up.

[@sevenacregreen]

When a large company installed solar on my house, 6 years ago, they ran the DC to the inverter down the cavity from roof to the garage wall. 350V and 5kw peak. Appeared to be their standard practice.

[@SpNick3]

I’ve seen this done many times by solar installers

[@SJM689]

I was always taught external cavities are a no-go area and internal cavities are only if you have to, and there aren't any other solutions. Modern building methods present numerous issues when rewiring/re plumbing but there is normally a sensible solution to each problem. The best thing I find is to explain to the customer what is going to happen ie. Chases etc and if they aren't happy you can just walk away.

[@alreadynuked]

This video came out only a short while after a KZbin electrician ran tails in the cavity which had polystyrene beads in the cavity. To protect the tails they wrapped it in tape.

[@efixx]

Haven't seen that one, who was it?

[@alreadynuked]

@@efixx kzbin.info/www/bejne/gqbGn6p9lqaknc0

[@chrisrogers2848]

To be fair, they only ran the tails THROUGH the cavity protected by tape. The original tails ran in the cavity I believe, but they drilled straight through the wall and fed the new ones in.

[@kevinpickett7249]

We use to run cables in a conservatory dwarf wall all the time and it’s the only way on a finished brick wall ( clients get the hump if you trunking the new wall 😃) perhaps using FP 200 could be the answer.

[@Yousitech]

I live in America, most of that is academic in my mind. I've seen some really shit electrical never have a problem. I think code is definitely best practice but if you cut the right corners it will still be just fine

[@andrewsmith9933]

The bit about the cable bridging the cavity is clearly nonsense as any cable that crosses the cavity from inside to outside such as to an outside light, socket, incoming telecoms service, SKY etc. would be the same and how many buildings have electric fixtures on the outside (clue almost all of them!). If moisture were to come into contact with the cable it could track down it and so it would be sensible for cables to only go up from the outside fixture so any moisture I directed to the outside wall leaf not the inside.

[@djb774]

I think it’s acceptable to run directly, (perpendicular to the internal wall) to an outside socket or light although I take the point about protecting the 75mm of exposed PVC, but the biggest argument for me is the poor old builder or DIYer who is outside up his ladder knocking out a brick with a bolster, he’d be forgiven for not expecting to come across a 10mm shower cable in the cavity, especially pre RCD days!

[@shausen1179]

What can't be seen can't be enforced. Also, the brick ties will hold up the cable.

[@efixx]

🤦🏻‍♂️

[@CCCP8888]

If cavity-wall insulation is to be used ; there SHOULD be a LARGE air space gap in-between the face of the insulation and the OUTER WALL inside the cavity-wall ; this includes an air space gap in-between the face of the insulation and the cavity-wall-tie drip point in the centre of the cavity-wall. Ask N.V.Q. BRICKWORK teachers for PROOF of this !

[@rogergregory5981]

Electricity board had been doing it on probably thousands of houses rewires back in the day you ought to see some of holes left in floor joists total butchers, not much in the way of insulation in them times till you get blown insulation doh

[@TheManLab7]

Who the hell is going to use pyro, just a drill through a well to stick something on the outside? Unless you have sex with the regs, then NO SANE PERSON will do it. Because it's just a pain in the arse. I do really like watching your videos and I know you have to abide by the regs, but just remember that the regs, aren't the law! It's just a guide on how things should roughly be done.

[@jameshansing5396]

Roughly being the key word… 🤭

[@treborriam]

Running a cable in the cavity is a non starter and I would bounce any electrician that would suggest it.

[@SaltCollecta]

Use conduit? Fucking hell.

[@stevensmith4449]

No Sharp edges and damp

[@tonycapone2016]

Mice love cables to gnaw on .

[@raychambers3646]

Cant put my outside lights up !

[@scabthecat]

You'll have to run an extension lead through your letterbox.

[@Easydread]

You need to get with the times.... your outside lights should be led with battery power & solar panel built in to recharge 🤣

[@AsadMulla]

@@Easydread add a mini wind turbine for good measure

[@efixx]

😂 Solutions!

[@efixx]

Sorry Ray! 😂