new build outside light

[GPack]

Hello, What is the correct way of running the cable for an outside light as per regulations and good practice?
I have a timber frame building with a 50mm cavity and outer leaf brick work. Is it okay to run the cable from the loft, down the cavity and through a hole in the brick work? or could you just drill a hole straight through the brick, cavity breather membrane then ply of timber frame, then up to the loft space?
Thanks for your help.

 

[markc123]

with over 100posts on an electricians website, i would of thought you'd know the answer to this question.

The idea of running cables in cavity walls absolutley stinks - see it now and again and can't stand it. I'd hate to think that a proffesional electrician would do it. Bad, bad practice IMO.

 

[telectrix]

poor practice, yes. but is it not worse to compromise the membrane? i'm not sure of that, but was once told by a BI that it was verboten.

 

[GPack]

Mmm. Thanks for the critique. Leaves me none the wiser though. What is the best way to it?

 

[telectrix]

check with your house builder if it's OK to pierce the membrane. if not, then it's up to the attic on the inside and surface on outside. use black flex on the outside.

 

[drew35]

They don't worry about shoving SVP, Sky cables, Air vents, water pipe, gas pipe through.

Straight through both skins for me.

 

[Stroppy]

We have been doing an estate of timber-framed houses and have been told that we can breach the membrane to get outside, but have to make good with silicone sealant to restore the air-tightness, which seems reasonable.

 

[telectrix]

a good sqirt of expanding foam should do the trick. when it oozes out from the cavity through air bricks, you know you've put enough in.oh, poo. thought this was a builders' forum.

 

[Robotstar5]

We have been doing an estate of timber-framed houses and have been told that we can breach the membrane to get outside, but have to make good with silicone sealant to restore the air-tightness, which seems reasonable.

As long as it's not the type that attacks the PVC sheath?

 

[Stroppy]

I didn't know there was an issue with that. Doing a quick search brought up this thread: http://www.electriciansforums.net/e...ical-forum/4805-sealing-silicone-sealant.html which is inconclusive, and a web search brings up a cable manufacturers Q&A which says there is no problem.

 

[Rockingit]

I do loads of timber frame, and as it seems to be the next generations method of choice then get used to it!

It's better practice to have first fixed it right to start with and run your cable in behind the vapour barrier, but either way it's just the normal downwards drilled hole straight through whatever is in the way and out the other side, insert cable, insert some foam around either end to reseal. Job done. Would normally take me about a minute. Remember to allow for screed and render depth on the outside wall so that where you've brought the cable through isn't directly behind where you'll need to second fix the light and drill through your own cable!

 

[Engineer54]

All i know is breaking the vapour membrane without positive resealing is a complete No, No!!

I'd personally never buy a wood framed house, or build an extension with this system for love nor money!! lol!!

 

[Stroppy]

Next they will be bringing in 'eco-plaster' made of mud and all that straw and horse-hair that goes to waste!

 

[Rockingit]

All i know is breaking the vapour membrane without positive resealing is a complete No, No!!

I'd personally never buy a wood framed house, or build an extension with this system for love nor money!! lol!!

Well, both architects and environmentalists seem to like it for a number of reasons; U values, sustainability, carbon output.....oh, sorry, I forgot: You're doing projects in China.

 

[PEG]

Nowt wrong with timber frame as long as you can accept that in the same way seeing a nice vintage car still running about on the highways and knowing it won't be happening with the car you drive.A flood,small fire or passage of enough time and it's time to build something new.It's why i collect anvils for a hobby...longevity rules:clown:

 

[Bonner]

Just contact with the builder who have installed the light and in my opinions without doing experiment just call to any good electrician also.

 

[Brightspark2]

Well, both architects and environmentalists seem to like it for a number of reasons; U values, sustainability, carbon output.....oh, sorry, I forgot: You're doing projects in China.

Now now...

 

[Engineer54]

Well, both architects and environmentalists seem to like it for a number of reasons; U values, sustainability, carbon output.....oh, sorry, I forgot: You're doing projects in China.

Of course they do, but the main reason they like them, is building cost, and how fast they can be thrown up, not necessarily the reasons you give!! Those vapour membranes, are critical!! loss of it's integrity and and rot and damp will follow. And with the timber sizes that they use these days, it wont take long to rot through!! Give me a conventional built building every single time!! lol!!

Nothing wrong with the concrete framed, block infill buildings on this project!! lol!!

 

[telectrix]

another few years, we'll catch up with the stone age tribesmen in africa, building houses from straw and mud.

 

[Stroppy]

Next they will be bringing in 'eco-plaster' made of mud and all that straw and horse-hair that goes to waste!

Plagiarist!

 

[Rockingit]

Of course they do, but the main reason they like them, is building cost, and how fast they can be thrown up, not necessarily the reasons you give!! Those vapour membranes, are critical!! loss of it's integrity and and rot and damp will follow. And with the timber sizes that they use these days, it wont take long to rot through!! Give me a conventional built building every single time!! lol!!

Nothing wrong with the concrete framed, block infill buildings on this project!! lol!!

I'm not disagreeing with you, but if you take a step back and think about it, any component of a building system is 'critical' these days so what's with singling out just one method?

 

[kw1980]

Drill down into kit, then straight through both skins, including vapour barrier. Then all you need to do is cover over the hole you have made with an appropriate tape. Aluminium foil tape works, or I have also used another cloth like tape (this was more suited to a passive house type environment)

 

[Rockingit]

Drill down into kit, then straight through both skins, including vapour barrier. Then all you need to do is cover over the hole you have made with an appropriate tape. Aluminium foil tape works, or I have also used another cloth like tape (this was more suited to a passive house type environment)

You're assuming that it's not been boarded already! If you can be close enough to tape the barrier then you're close enough to do the job properly and not need to puncture it in the first place.

 

[kw1980]

Jobs I work on come out of a factory pre-fabricated with vapour barrier already in place. And the job does get done properly!

 

[Rockingit]

Jobs I work on come out of a factory pre-fabricated with vapour barrier already in place. And the job does get done properly!

How/where do you tack cable then? Do they come with an additional 20-30mm battening before boarding to create a services void? Am assuming the joist space is packed with kingspan? (Genuine question btw, it's something we struggle with all the time if there's no batten space!)

 

[kw1980]

Yes, they come with 40mm battens running vertically, cables are ran as normal through floor joists then down inside service zones. 1st fix joiners fit top and bottom runners before attaching plasterboard. The wall panels and roof panels come pre-insulated so no Kingspan in between joists.

 

[ayjay]

all these posts on such a basic q from a poster that has ect

its a ****take

 

[Rockingit]

Yes, they come with 40mm battens running vertically, cables are ran as normal through floor joists then down inside service zones. 1st fix joiners fit top and bottom runners before attaching plasterboard. The wall panels and roof panels come pre-insulated so no Kingspan in between joists.

Lucky you! We normally end up with a bun-fight for the last 20mm left on the joist to clip to before VB stapled over and then boarded. But this is just 'normal' vapour barrier not Passive House. Did a Passiv a couple of years ago but it was a self-build on site so we got the first bite whilst the frame was still open. Was still a complete PITA though!

 

[Rockingit]

all these posts on such a basic q from a poster that has ect

its a ****take

Well if you care to actually read them you'll find that the last 50% has been valid discussion on the relative points of timber frame construction - I hardly call that taking the pi55.

 

[kw1980]

Usually work with normal vapour barrier, have only done one job with a passive house set-up. Came out of the same factory, same set-up regarding joists and service zones. Different tape used was the only difference for me, but the joiners had a real hard time passing the air tightness tests.

 

[DPG]

all these posts on such a basic q from a poster that has ect

its a ****take

Ayjay, have you ever posted anything useful or helpful? Daz

 

[Rockingit]

Ayjay, have you ever posted anything useful or helpful? Daz

Not that I can think of!