This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Running conduit in very shallow screed

Former Community Member
Former Community Member
Hi,


I am preparing the kitchen in my flat for a rewire and need to run cables for 2 x ovens plus dishwasher, washing machine, fridge freezer etc. 


The flat has solid ceilings and   floors and CU is on opposite side of the flat from the kitchen so running cable is a challenge. When we rewire the rest of the electrics, the sockets and lights are likely to go either behind coving or chased into plaster, but this is not really feasible for the kitchen cables. 


I’m thinking my best option is to go through the floors. I recently dug a massive chase for a gas pipe (which in retrospect should have been made bigger and I could have run the cables through that). In doing so I discovered that the screed is only 30mm thick and delaminates from the underlying concrete really easily with a good whack from an SDS. The concrete is obviously MUCH harder work to get through (a few days work with a heavy duty saw plus annoying the neighbours and filling the flat with dust). So what I want to do is cut the screed with a grinder to 30mm deep to make a channel and run the cable in that. 


I’ve got a couple of ideas of how to do this but not sure what is permitted - is it ok to run cable at such a shallow depth? - or what would be best. 


Option 1 - SWA cable laid straight in the channel and mortared over. Obviously will never be coming out so difficult to replace without pulling the floors up but the easiest to install. 


Option 2 - 20mm high impact pvc conduit with 3 x singles in each run. I’m assuming that because there will be 4 x 90degree bends in the route that these cables will also be impossible to remove once installed but will at least be protected by the conduit from damage while the mortar is applied/sets. I’m also assuming that even at a very shallow depth this conduit will be ok to walk over once set in mortar with flooring over the top. 


Option 3 - something completely different. 


Any advice would be greatly appreciated. I do want to make clear I’m not actually planning on doing the wiring work, I just want to get cables in situ for an electrician to be able to work with at a future date. I just want to do this bit ahead to avoid digging up the floor again at a later date. 


Thanks,


Patrick
Parents
  • Former Community Member
    0 Former Community Member
    Thanks for the reply. 


    I’ve had a read through the relevant sections, I can’t see anything that would prevent the use of SWA buried direct and screeded over as long as I get the radius on the bends correct. 


    Protection from water and corrosion would be covered by the properties of the sheathing on the SWA cable? And if not presumably plastic sleeving of some sort would do? (“Suitable protection for application during erection may include protective tapes, paints or grease.”) Impact should be covered by the steel armouring. 


    Regarding intended use, I can’t imagine that walking on a floor would damage SWA once buried in screed: “ A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor.” But my reasoning for thinking conduit might be better was that the impact of any movement in the slab or filling mortar could potentially cause damage? 


    To be honest I would prefer to avoid using conduit so it seems that SWA buried is the best option. I just wasn’t sure if there was a regulation that specified conduit was a necessity in an installation in screed. 


    I will be getting an electrician in to discuss before I start, I just wanted to get an idea of the regs before having someone come in, because what I don’t want is an electrician to tell me something like “bury some T&E and screed over it” and then I do it and lay the floors and then someone else won’t sign it off if I end up using a different contractor. Plus I like to get an idea of what I’m getting myself into and if it sounds like a major job (eg metal conduit which I hate cutting threads on) then I’ll just leave it alone. But if I can just dig out and bury some SWA then this is easily doable so I’m happy to do it myself. 


    So thank you all for you advice, I appreciate you taking the time to help me out. 


    Cheers,


    Patrick.
Reply
  • Former Community Member
    0 Former Community Member
    Thanks for the reply. 


    I’ve had a read through the relevant sections, I can’t see anything that would prevent the use of SWA buried direct and screeded over as long as I get the radius on the bends correct. 


    Protection from water and corrosion would be covered by the properties of the sheathing on the SWA cable? And if not presumably plastic sleeving of some sort would do? (“Suitable protection for application during erection may include protective tapes, paints or grease.”) Impact should be covered by the steel armouring. 


    Regarding intended use, I can’t imagine that walking on a floor would damage SWA once buried in screed: “ A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor.” But my reasoning for thinking conduit might be better was that the impact of any movement in the slab or filling mortar could potentially cause damage? 


    To be honest I would prefer to avoid using conduit so it seems that SWA buried is the best option. I just wasn’t sure if there was a regulation that specified conduit was a necessity in an installation in screed. 


    I will be getting an electrician in to discuss before I start, I just wanted to get an idea of the regs before having someone come in, because what I don’t want is an electrician to tell me something like “bury some T&E and screed over it” and then I do it and lay the floors and then someone else won’t sign it off if I end up using a different contractor. Plus I like to get an idea of what I’m getting myself into and if it sounds like a major job (eg metal conduit which I hate cutting threads on) then I’ll just leave it alone. But if I can just dig out and bury some SWA then this is easily doable so I’m happy to do it myself. 


    So thank you all for you advice, I appreciate you taking the time to help me out. 


    Cheers,


    Patrick.
Children
No Data