Routing cable in concrete floor...Help.please..

Kenny · Post by **Kenny** » Tue Mar 13, 2007 10:50 pm

Can any kind sparky help me....wots the deal with cable in concrete floor..
Wot depth?...metal or can i use plastic conduit if so?is only a 2 metre run.
No floor boards and walls have just been plastered!!!!

Also i have replaced some cable in the ring main and the original looks like 4mm,(1970's wiring!)Is def a ring main!!!!!!!! and i have put 2.5 mm in ,in a few places ..is that ok mixed like that?????

Cheers people.

sparkydude · Post by **sparkydude** » Wed Mar 14, 2007 6:15 am

I would use plastic conduit and set it at whatever depth you can. if you have a structural slab and the screed is still to be laid then fix it to the slab and it will be below the screed. Your wiring is probably the older twin and earth with imperial sized conductors , when you say it looks like 4mm is that from outside or the core size ? Outside size will be pretty similiar to 4mm , and the internal cores will be more like 2.5mm maybe a little larger,but thats due to insulation thckness normally. If it is a 4mm ring then you should have extended/altered it in the same as there might have been a reason why it was done in this size cable.

Nick

Kenny · Post by **Kenny** » Wed Mar 14, 2007 8:50 pm

Hi Nick....i'm putting the cable in floor.....is not a slab or a whole new layer of concrete...
Had a closer look at the cable....ur rite...from the outside it looks the same size as 4mm...but the cores them selfs r not as thick as 4 mm and not quite as thin as 2.5mm...assume it is a 2.5mm there bouts then!!

Mmm...i don't know what to do now...most of the circuit is new apart from a few metres here and there...
Should i leave the orignal cable OR lay some in the concrete floor....Dust is not a problem if i come to hacking the floor up!!!

should have thought of this b4 the walls got plastered!...Ha!

Ta.

sparkydude · Post by **sparkydude** » Wed Mar 14, 2007 8:54 pm

If you are saying there are a few meteres of old cable here and there and the rest is new then if i was you i would still rewire these, as then you know the circuit is 100% all new and no possible dodgy bits in the circuit. If you are needing to bury it into existing concrete screed, just get a 9 inch grinder with diamond disk, sheet up the room to stop the dust from going everywhere and grind away. Then just bury the conduit in som e cement when you backfill the chase. Then before carpeting or floring , spray the floor with some red paint to indicate your cable routes, and warn of its presence for future. Where the conduit goes upto the sockets, buy a bending spring and form proper bends in the conduit uptio the backboxes.

Nick

Kenny · Post by **Kenny** » Wed Mar 14, 2007 9:10 pm

Right...thats wot i'm thinking...bit pissed off really...is only a tiny 1 bed flat (my first house!)...thought from the start it was gonna be a paint up and new kitchen.....but it changed along the way!!!!!!...this and that needed doing..should have just got it all rewired...b4 the plastering.

I've got a grinder..is a 4inch tho...Isn't all that hard anyway the concrete.

Take it u mean plastic and not metal conduit?!

Cheers

sparkydude · Post by **sparkydude** » Thu Mar 15, 2007 6:46 pm

yes plastic is what you need, and a bending spring to bend it aswell.a 4 inch grinder should be ok, just buy a cheap diamond blade from aldi they have a pack of 3 for 3.99 at the moment should do your needs perfectly.

Nick