Concrete ceiling dry lined....

[NozSpark]

Got a job that I'm quoting for (well estimating really) in an ex council house.

They are converting the old out houses into a kitchen. It has a concrete ceiling which they are wanting to dot & dab.. now I would prefer them to fix some 3 x 2 (min) to it and then borad over.

So to the point.. any cable in the ceiling will be < 50mm and there are no zones, so what are my options???

Steel conduit or force them to use some 3 x 2???

Obviously all circuits will be RCD protected

 

[ProDave]

RCD is all you need.

If you are worried, steel capping.

Perhaps the ceiling is already low, which might be why they don't want to batten it first, though that would be easier for all trades if they did that.

Apart from anything else, I'll bet there's no insulation in that concrete ceiling. Battening it would allow them to fit at least 50mm of kingspan

 

[Adrian]

Ive rewired loads of council flats that had concrete ceiling and we wired everything around the walls and put coving over it to cover it,I made more money on the coving at the time than i did wiring it

 

[NozSpark]

RCD is all you need.If you are worried, steel capping.

Perhaps the ceiling is already low, which might be why they don't want to batten it first, though that would be easier for all trades if they did that.

Apart from anything else, I'll bet there's no insulation in that concrete ceiling. Battening it would allow them to fit at least 50mm of kingspan

What's the stel caping for?? I can understand 3mm steel plate, but capping is not suitable mechanical protection...

TBH I was going to be making use of the 150mm wall/ceiling zones (don't like it, but there isn't much choice) and there will not be any insulation

 

[Lurch]

TBH I was going to be making use of the 150mm wall/ceiling zones (don't like it, but there isn't much choice) and there will not be any insulation

As long as it's to the regs doesn;t really matter. As everyone keeps banging on about you have to follow the 17th edition to the letter so your arse is covered, doesn;t matter if you feel the regulation is daft or unsuitable, as long as your doing the job to the current standards it doesn;t matter how safe\dangerous an installation is.

 

[spinlondon]

What is the significance of the 50mm and the steel conduit?

Why can't you just fix your cables in position to the concrete ceiling, then cut holes as required in the plasterboard?

 

[ProDave]

What's the stel caping for?? I can understand 3mm steel plate, but capping is not suitable mechanical protection...TBH I was going to be making use of the 150mm wall/ceiling zones (don't like it, but there isn't much choice) and there will not be any insulation

Steel capping is not sufficient to remove the need for an RCD. But in the REAL world, anyone trying to hammer a nail in and hitting steel capping is very very much less likely to penetrate the capping and hence penetrate the cable, and go and look for somewhere else to insert the nail. But in the real world, people tend not to hammer nails into a ceiling, like they do into a wall.

If you rely on the 150mm wall / ceiling zones, then unless you only have lights at the perimeter of the room, somewhere the cables are going to be outside of a safe zone. That's unavoidable.

But 17th states, amongst many contradicting things, that RCD protection is needed for ANY cable outside safe zones. Which I have argued negates safe zones altogether, because if that clause is taken literally, you can run cables absolutely anywhere you like as long as there's an RCD.

I was thinking the other day just how stupid the regs are in some situations. There was a photo on the rogues gallery of a nail almost penetrating the cable from a light above a picture. Thinking about it, if you have a light on a wall above a picture, then the very last place you want to run the cable is vertically down from the light because that's where the fixing to hang the picture will be, but the regs force you to run the cable vertically, where it's in most danger, rather than along a bit then down.

 

[Lurch]

Steel capping is not sufficient to remove the need for an RCD. But in the REAL world, anyone trying to hammer a nail in and hitting steel capping is very very much less likely to penetrate the capping and hence penetrate the cable, and go and look for somewhere else to insert the nail.

I would have to disagree with that and say that most people hammering nails in expect there to be something in the way so just whack it as hard as they can. It barely takes any effort to nail through metal capping, especially when it is held rigidly in a finished surface.

 

[Andy™]

Steel capping is not sufficient to remove the need for an RCD. But in the REAL world, anyone trying to hammer a nail in and hitting steel capping is very very much less likely to penetrate the capping and hence penetrate the cable, and go and look for somewhere else to insert the nail. But in the real world, people tend not to hammer nails into a ceiling, like they do into a wall.

dont know which world you live in, but in this one, many sparks hammer the nail through the side of the capping and then into the wall to hold it in place...

 

[spinlondon]

But 17th states, amongst many contradicting things, that RCD protection is needed for ANY cable outside safe zones. Which I have argued negates safe zones altogether, because if that clause is taken literally, you can run cables absolutely anywhere you like as long as there's an RCD.

No it doesn't, RCD protection is only required for cables within safe zones.

 

[Apache]

Got a job that I'm quoting for (well estimating really) in an ex council house.They are converting the old out houses into a kitchen. It has a concrete ceiling which they are wanting to dot & dab.. now I would prefer them to fix some 3 x 2 (min) to it and then borad over.

So to the point.. any cable in the ceiling will be < 50mm and there are no zones, so what are my options???

Steel conduit or force them to use some 3 x 2???

Obviously all circuits will be RCD protected

Noz - though the rule was 50mm in WALLS - you can go where you like on the ceiling?!

No issue?

 

[spinlondon]

Not quite, there's a 50mm depth rule about cables through joists.

 

[ProDave]

I would have to disagree with that and say that most people hammering nails in expect there to be something in the way so just whack it as hard as they can. It barely takes any effort to nail through metal capping, especially when it is held rigidly in a finished surface.

Very true, which is why as I said steel capping does not remove the need for RCD protection.

All I was saying is steel capping provides some level of protection from nails and is better than nothing. That is all I was saying. If you think it's level of protection is negligible, then don't use it.

 

[ianmacd]

Capping is only used to protect the cable from the plasterer although becasue you want him to cover it up he probably won't unlike those new boxes you just sunk in somewhere on that wall.

 

[ian932]

Not quite, there's a 50mm depth rule about cables through joists.

But there is no joists and the vet is 100% correct the ceiling has no zones the 50mm is to avoid nails and screws hitting cables when the ceiling and floors are fitted 522.6.5

Noz run them as sensible as possible and make a sketch to attach to the EIC and note it on the EIC that there are cables below the surface.

Capping is a waste of time IMO you don't even know you've hit it as its so wafer thin.

A thick strip of fibre glass cloth would be better for drills and screws a bit like the old chainsaw trousers principle, it snags up the drill or screw. (that