chasing into concrete screed floors - a risk to the neighbour's lights?

[laike]

i live in a 1960s built ex-local authority flat. the floors are concrete with approx 30mm of screed poured on top, brick walls. the existing cabling is all MICC which i'm considering ripping out, not because it doesn't work but because i'm looking to move some walls and chase new central heating pipework into the concrete floors. am pretty certain this is going to nick an MICC cable and the circuit will be screwed. not to mention it's not much more expensive to do a full rewire than to find someone who can repair MICC.

QUESTION:if i'm chasing into the screed to run my new cables, is there a risk that i could cut the neighbour's below me lighting cables? is there a chance their lights are running through my screed? (if not, how did they possibly run their lights to their bedroom as their ceiling / my floor is concrete?)

really frustrating job this, if there are any certified NICEIC sparks reading this who are keen to take it on, get in touch. location: dalston, london.

 

[somersetsparks]

:angry_smile:

Sorry grumpy, it is a bank holiday Saturday and all! lol If you have got a 10mm skim of plaster, you could cut wide chases, borrow a nail gun and fix cables up in capping, even better metal capping, then get a friendly plaster (could also be a not so friendly plaster the choice is yours!) to patch the areas and then possibly re skim the whole ceiling for the modern clean look, or just get him to patch and artex it for the 'local authority' look. n

 

[Guest55]

:angry_smile:

what do you want us to say ?

you'll never get the chase depth needed for pvc conduit , the render / screed is only thick enough to cover the pyro & gland ( about 12mm )

and you'll make a complete mess of the structure in the attempt.

so unless youve got an incredibly compelling reason for not fitting a false ceiling then youre all out of luck.

 

[ipf]

Gonna be interesting when it comes round to installing the recessed light fittings :sweatdrop:

 

[KAS1]

I know the answer, cornice lol trunking around the bedroom walls with fittings installed like in HMP whitemoor and the like

 

[laike]

as to the OP , looking at those photos , you're in for a whole heap of aggro trying to chase the cement render off a concrete ceiling.

so i'm dealing with concrete slab ceiling, with MICC surface mounted and covered with a 10 mm layer of concrete 'render' (not a term i'm familiar with)? it appears to be much harder than plaster, stabbing it with a knife barely marks it.

ok, good to know your enemy... cheers

you'll never get the chase depth needed for pvc conduit , the render / screed is only thick enough to cover the pyro & gland ( about 12mm )

and you'll make a complete mess of the structure in the attempt.

forget the conduit, are you saying chasing the 10mm 'render' just to fit the cable, then plastering over is a no go? why not?

 

[Guest55]

i dont see why not , so long as those circuits will be rcd protected.

you could consider oval pvc conduit , it lays flat at around 10mm ish.
lay 2 lengths to each light point and skim over.
thats what i'd probably do.

 

[laike]

done. going to propose that solution. thanks a million. i don't want 30+ m2 of false ceiling!

btw, how the hell did they get the concrete render to stick to the poured in slab? it's so perfectly smooth as well.

so we're sure it's safe to chase that? i don't want the council bitching about structural compromisation.

 

[UNG]

it's a 2 story, ex council, 1960s built flat. with brick walls, concrete floors, and MICC cabling (to be ripped out for the rewire).

see pics.

View attachment 18865View attachment 18866View attachment 18867

structural report extract

We understand that you wish to run further new services within the screed layer. We can confirm that this will not affect the structural performance of the concrete floor slab. However, it should be ensured that the screed is broken out carefully (not with an angle girder or similar) to ensure that the concrete surface of the floor slab is not damaged or cut into.

I think that statement precludes drilling through the slab

pulled off one of the ceiling mounted pull cords

View attachment 18876View attachment 18877View attachment 18878View attachment 18879View attachment 18880

there appears to be a layer of plaster (?), 10mm deep on the ceiling? i thought it was concrete as it is very hard.

Looks like the old pyro octopus system has been used originally

what do you want us to say ?

you'll never get the chase depth needed for pvc conduit , the render / screed is only thick enough to cover the pyro & gland ( about 12mm )

and you'll make a complete mess of the structure in the attempt.

so unless youve got an incredibly compelling reason for not fitting a false ceiling then youre all out of luck.

Plaster depth pyro was never glanded it was terminated with a pot and the pot was clamped into an accessory box designed for pyro to maintain earth continuity

done. going to propose that solution. thanks a million. i don't want 30+ m2 of false ceiling!

btw, how the hell did they get the concrete render to stick to the poured in slab? it's so perfectly smooth as well.

so we're sure it's safe to chase that? i don't want the council bitching about structural compromisation.

If you mix a bit of PVA into the cement mix it will be nice and smooth when trowelled up, coating the chase with a 5:1 water / PVA mix before filling it in will help the adhesion as well works

 

[ayjay]

why do you need to rewire the flat?micc lasts forever

 

[ipf]

Sixties wiring, shortage maybe ? Sick to death of extension leads all over the place ?

 

[ayjay]

nothing wrong with 60s micc imo
doubht if theres any shorts
i,m only talking about the lighting so extension leads arn,t needed
cheers

 

[ipf]

nothing wrong with 60s micc imo
doubht if theres any shorts
i,m only talking about the lighting so extension leads arn,t needed
cheers

Say so then.
I'm not saying there's anything wrong with the wiring, just that in the sixties, nothing like as many appliances were readily available, hence, not as many sockets were required.

 

[laike]

why do you need to rewire the flat?micc lasts forever

fair question and sadly it doesn't *need* rewiring. but i'm moving a wall so 2 MICCs need moving. there's also (newer) surface trunking that looks crap and can't be chased due to the recessed MICC. and it would be nice to move a few switches and sockets. i'm doing the rest of the flat too so figure to do it all. feel conflicted about it though.

 

[ayjay]

personally jaike, and in my past experience(45 years) micc wired flats in the lighting is always fine although it will need testing-- if it works its good to go(imo)
socket-wize in old flats there wernt many!
one way is to run a new ringmain in plastic skirting trunking, also computer stuff ect
no need to mess about with the lighting

 

[laike]

question guys: can i chase the floor in front of the fuse box without fear of hitting the incoming mains? you can see 1 of those incoming mains looks to go into the floor in some direction (down?) where is the other incoming mains? or is there only 1 that splits between the 2 meters? FYI the council pay the bill for the lower meter as that's the UF heating included on the service charge.