Ring Final Cable Routing Through Bungalow Loft

[Amateur]

Hi all. I know there is a DIY forum but im really after your expert knowledge rather than fellow DIY'ers/amateurs.

With regards to replacing a section of a bedroom ring final circuit in a bungalow loft what is your preferred method of cable routing taking into account insulation and not being able to drill joists/trusses?

Currently the cables are running all over the place and clipped on the top of joists which then the previous home owner has deemed the clips sufficient support for boards to sit on top of!!!

The fact you cant drill the trusses how do you prefer to get across the joists at 90 degrees when there is insulation too? Do some of you lay cables on top of the insulation in the eaves to avoid any issues with potential damage from the usual loft storage items?

Im finding a lot of mixed opinions on this after a bit of Googling due to the thermal issues of the cables being under insulation and then the risk of damage to cables clipped on top of the trusses when they have to cross them as opposed to being clipped along the sides.

Hopefully some of you pros can share some of your knowledge and preferred methods on this.

Thanks.

 

[Amateur]

a trick i have used in the past, in lofts, is to run some 4" plastic guttering ( upside down) over the cable/s and under the insulation. this gives the cable/s space to lose any heat.

I bet that could get expensive. If the fella isnt happy when he comes to to connect and test then i will put that idea to him. I would need a good few lengths! Im hoping it will be fine as is though.

What do they do with regards to cable runs in new builds with all that insulation, anyone know? Ive read that it is not an issue with lighting circuits only ring final, showers, cookers etc.

 

[Amateur]

a trick i have used in the past, in lofts, is to run some 4" plastic guttering ( upside down) over the cable/s and under the insulation. this gives the cable/s space to lose any heat.

I bet that could get expensive. If the fella isnt happy when he comes to to connect and test then i will put that idea to him. I would need a good few lengths though! What do they do with regards to cable runs in new builds with all that insulation, anyone know? Ive read that it is not an issue with lighting circuits only ring final, showers, cookers etc.

 

[Ian1981]

Strictly speaking cables can be run in insulation it's just that you may need to increase the CSA of the cables such as 4mm for your ring final circuits.
It all depends how much insulation is in fact covering the cables and what circuits, in particular shower circuits installed in 10mm were installation method 101 de-rates the cable to a mear 36 amps.

 

[Amateur]

In this case all i am doing is removing an existing extension of the 2.5mm ring to replace it with new to allow for sockets where we actually want them before the 2 bedrooms are replastered.

The original cables were buried in insulation in places, not clipped to joists. In other areas they were sat on top of the joist with boards laid over and sat directly on the cables! Not to mention that someone had spliced into the ring and then run 3 spurs (3 separate cables) from the one jb. They also had the cables running through the same hole in the wall as the heating pipes. All in all if nothing else i have made it safer by ripping it all out and starting again.