Cables run in cavity between block and brick of an internal wall

[knighty]

Hello,

I'm currently in the process of building a side extension. I will be putting in 2 new rings and 2 new lighting circuits. To get them from the CU to the extension I wanted to run them in the cavity of the old external wall (now internal because there is an extension on the other side). I have cut a door way between the old and new parts of the house adjacent to the CU. I can therefore see easily into the cavity and could probably put the cables in a conduit and avoid any damage to them being pulled through the brick work or rubbing against sharp or rough surfaces. Apart from checking the current carrying capacity with the correct reference method would this method of installation be acceptable under inspection?

Many thanks for any help.

Jon

 

[telectrix]

do you mean to fit the cables straight through the cavity wall, or run up/sideways/whatever in the cavity?

 

[Andy78]

This work should be carried out by an electrician.

 

[Pete999]

Hello,

I'm currently in the process of building a side extension. I will be putting in 2 new rings and 2 new lighting circuits. To get them from the CU to the extension I wanted to run them in the cavity of the old external wall (now internal because there is an extension on the other side). I have cut a door way between the old and new parts of the house adjacent to the CU. I can therefore see easily into the cavity and could probably put the cables in a conduit and avoid any damage to them being pulled through the brick work or rubbing against sharp or rough surfaces. Apart from checking the current carrying capacity with the correct reference method would this method of installation be acceptable under inspection?

Many thanks for any help.

Jon

Crikey how big is this extension? 2 RFCs and 2 Lighting circuits, are you sure this not a bit overkill?

 

[telectrix]

This work should be carried out by an electrician.

agreed. the extension will be subject to building control and they will want oodles of cash if OP is not qualified.

 

[knighty]

Thanks for the quick responses. I'm not an electrician but will be doing the work myself and have paid the extra for not being a competent persons and getting building control to sign it off. The extension is a 2 storey side so I want a lighting circuit for upstairs and down, and it also contains a utility room which I want on a separate ring. I'd like the cables to run up inside the cavity from the consumer unit (which the existing house wiring already does when built in the 70's) and then into the floor space of the extension. From there I can run them to everywhere I need. The alternative is channel out the wall above the consumer unit and put in conduit, plaster back over the top. The later is a messier option

 

[telectrix]

'd like the cables to run up inside the cavity from the consumer unit (which the existing house wiring already does when built in the 70's) and then into the floor space of the extension. From there I can run them to everywhere I need. The alternative is channel out the wall above the consumer unit and put in conduit, plaster back over the top. The later is a messier option
either option is OK, but if run in the cavity, cable support might be an issue.

 

[Pete999]

Thanks for the quick responses. I'm not an electrician but will be doing the work myself and have paid the extra for not being a competent persons and getting building control to sign it off. The extension is a 2 storey side so I want a lighting circuit for upstairs and down, and it also contains a utility room which I want on a separate ring. I'd like the cables to run up inside the cavity from the consumer unit (which the existing house wiring already does when built in the 70's) and then into the floor space of the extension. From there I can run them to everywhere I need. The alternative is channel out the wall above the consumer unit and put in conduit, plaster back over the top. The later is a messier option

Why not install a 4mm2 radial circuit for the utility room and the same for the remainder of the socket outlets?

 

[telectrix]

i detest 4mm radials. give me a 7/029 rfc any day.

 

[knighty]

So where the new door way is I haven't put the door liner up yet so can get easy access to the cavity so could add some form of cable support easily enough. A radial for the utility room isn't a bad idea but i'll do the other sockets on an RFC.

 

[Pete999]

i detest 4mm radials. give me a 7/029 rfc any day.

OK a 7/036 Radial is that better Tel?

 

[telectrix]

at least the cable is stranded and flexible when cold.

 

[rolyberkin]

Okay so building control are overseeing but who will be testing and completing the certificate for design, construction and testing, that person needs to agree where the cables are being run, if your building control have a suitably qualified person to oversee your work then you will need to agree this with them not us!

 

[knighty]

Building control use a third party to do the testing, and not knowing who the individual will be until I call building control to tell them I'm ready and they organise it I was hoping to get a steer from this forum as to what could be suitable.

 

[Andy78]

Building control use a third party to do the testing, and not knowing who the individual will be until I call building control to tell them I'm ready and they organise it I was hoping to get a steer from this forum as to what could be suitable.

This person should be performing a visual inspection of the installation at the first fix stage so this needs arranging.

 

[DJ Ovengloves]

Take plenty of photos!

 

[rolyberkin]

It doesn't work like that, the person allocated by building control is responsible for design, construction and test. You should arrange a site visit with the contractor prior to starting works, after first fix and when you are ready to test and connect. The testing process for any installation should be constant and ongoing throughout an installation. A good example is where a customer of mine put two nails through dead cables (in safe zones) when plaster boarding, as we were testing as we went along we found the problem prior to plastering. Also never assume a cable is okay until tested, you could have a faulty cable and be undoing loads of building work to re run. This is why third party certification can sometimes a false economy.

 

[rolyberkin]

And as above take loads of photos!

 

[Ian1981]

Will your new cavity wall be getting cavity insulation installed in it?
I’d not run cables in a cavity if this was the case especially if it’s those polystyrene balls as it reacts with the plasticier of the cables and makes the insulation go all soft leading to possible faults.

Edit your protecting the cables with conduit
Must learn to read

 

[knighty]

Thanks for all the advice, I will give building control a call to discuss. Hypothetically though, what would happen if you bought a house without electrical certification. In this situation the tester wouldn't have done a visual inspection or be part of the design but would surely still be able to sign it off?

And separately the tester would be a competent person but say I'm confident of meeting Part P and BS7671 and take lots of photos and explain what I've done, so long as its correct would the inspector still be able to sign it off ? Clearly there is a big risk here of messing it up and it failing on safety, but also and as mentioned above runs the risk of simply not working and being covered up by plaster and made good.