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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
  • Advice for any more grooving of floors and walls. Hire a chasing machine for a day and a suitable vacuum cleaner. It then makes little mess, and virtually no dust in the air. So much better. I have a Makita one, really excellent with my Henry! A few mm into the floor will make no difference to the strength, this part is in compression and well strong enough. It is the underside, in tension, which could be damaged, avoid the reinforcement, which will be near the underside! 20mm steel conduit will do the job, whilst plastic will work, I always prefer steel buried in concrete. 10mm of strongish mortar over the top will finish the job. You say 4 bends, this is OK if you only have a small number of cables (small fill factor). Cable current rating installation method B from table 4D1A. Overall this is much easier than SWA, and tidier too, because SWA doesn't sit nicely in place whilst you fill in and is probably bigger in diameter!
Reply
  • Advice for any more grooving of floors and walls. Hire a chasing machine for a day and a suitable vacuum cleaner. It then makes little mess, and virtually no dust in the air. So much better. I have a Makita one, really excellent with my Henry! A few mm into the floor will make no difference to the strength, this part is in compression and well strong enough. It is the underside, in tension, which could be damaged, avoid the reinforcement, which will be near the underside! 20mm steel conduit will do the job, whilst plastic will work, I always prefer steel buried in concrete. 10mm of strongish mortar over the top will finish the job. You say 4 bends, this is OK if you only have a small number of cables (small fill factor). Cable current rating installation method B from table 4D1A. Overall this is much easier than SWA, and tidier too, because SWA doesn't sit nicely in place whilst you fill in and is probably bigger in diameter!
Children
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