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.

 

[sparksburnout]

Have you discussed it with the electrician you are going to employ to do the work?

 

[Amateur]

Ha. How did I know i was going to get an answer like that.

No, I havent yet. Im first fixing with a local firm making the connections and doing testing. I just like to get as much info as i can on any work i am involved in as ive found many differing opinions in the past across multiple trades due to my job.

 

[sparksburnout]

Ha. How did I know i was going to get an answer like that.

No, I havent yet. Im first fixing with a local firm making the connections and doing testing. I just like to get as much info as i can on any work i am involved in as ive found many differing opinions in the past across multiple trades due to my job.

So what happens if this "local firm" disagrees with your choice of cable routing then?

 

[Amateur]

Ha ha. Anybody else still up that doesnt mind offering their view on preferred routes?

 

[Strima]

Ask your local firm.

 

[davesparks]

How any of us would do it some irrelevant, it will be up to the electrician who is signing the certificate to decide how they want the job done.

I know how I would do it, but other people may not consider that to Ben the best way of doing it.

 

[Amateur]

Ha. Never mind. I will give them a ring in the morning. Usually a helpful lot on here, I guess i just picked the wrong time of day today.

Oh well. Goodnight.

 

[Sparky_marky2]

Amateur: Safer and faster to get a qualified electrician in if cables are "running all over the place and clipped on the top of joists" an electrician can give a better judgement after viewing the installation

 

[Amateur]

Amateur: Safer and faster to get a qualified electrician in if cables are "running all over the place and clipped on the top of joists" an electrician can give a better judgement after viewing the installation

Im ripping all that section out. The two rooms are an old extension on the bungalow, the ring was extended to provide outlets to the extension rooms. Im disconnecting at the jb's where they spliced in to isolate the rooms and then running all new cable to new socket positions and back to the jb's leaving the second fix (reconnection) and testing to my electricians. I will reinstate the rest of the house ring in the mean time.

I know lots of people come on here pretending they are getting sparks in for testing etc but this is not the case this time. I simply wanted other opinions on preferred routes.

I have done lots of first fixes in our last 3 houses but this is our first bungalow.

I will just give the firm a call this morning and see if they can allocate a spark (they have dozens) to my job so i can ask him direct what he personally would like to see.

Cheers

 

[Sparky_marky2]

Seems like you have experience on first fix wiring, theres not much difference in terms of wiring between a house or a bungalow and going into the loft so treat it as the same. With regards to the trusses if you need to run cable along/through insulation have you tried PVC conduit through the runs where it will be in contact with insulation?
Dependent on the number of cables you have going through the extension part of the house 25mm PVC conduit should be fine for the runs that are going through the insulation and better than just laying it on top of the insulation.

 

[Amateur]

Thanks for the reply Mark. I shouldve just got in the loft before starting this thread. A very considerate builder fixed timber spanning the joists under the perlin that is not in useable space. Ive clipped all cables along the sides of ceiling joists and gable walls where needed and along the back side of the timber when needing to cross the joists.

Just incase anyone asks the cables are clipped as high as possible to the sides of the ceiling joists (40mm ish from plasterboard) just incase any future Plasterer puts a screw/nail through them.

Cheers

 

[telectrix]

Thanks for the reply Mark. I shouldve just got in the loft before starting this thread. A very considerate builder fixed timber spanning the joists under the perlin that is not in useable space. Ive clipped all cables along the sides of ceiling joists and gable walls where needed and along the back side of the timber when needing to cross the joists.

Just incase anyone asks the cables are clipped as high as possible to the sides of the ceiling joists (40mm ish from plasterboard) just incase any future Plasterer puts a screw/nail through them.

Cheers

sounds OK from what you say, but only a looksee would confirm. the basics are:

1. route cables so that they will not be subject to mechanical damage.

2. avoid insulation where possible. cables may be down rated by as much as 50% if under insulation.

3. avoid the use of junction boxes unless absolutely necessary ( e.g. if you can't access the Consumer Unit or an existing socket/s ).

 

[Amateur]

1 and 3 are fine Tel but its 2 thats always going to be the issue as cables have to go under insulation at some point no matter how they are run. They are all clipped to the ceiling joists, timbers and walls rather than just laid across the plasterboard so that should help with the potential thermal issues shouldnt it? Obviously there is still insulation between the ceiling joists too but from what ive read the cables being clipped to the joists helps with that issue.

My loft is 4ft high at the centre and im 6ft5 19 stone so you can imagine the fun im having up there!!! Oh well, back to it!

 

[telectrix]

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.

 

[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.