Filling the hole in the wall with electrical cables

[lookieluke]

When renovating a guests' toilet I found, after removing ceiling plasterboard, a rather large hole in the inner blockwork behind the joist adjacent to the wall. The hole has a bunch of electrical cables going through it and obviously the cables run into the cavity. The main goal of the whole renovation is to insulate the room and obviously I have to fill the hole to make it airtight. I was thinking about using an expanding foam, but I've read somewhere (don't remember where exactly) that the ordinary polyurethane foam slowly reacts chemically with the cables insulation. Additionally the foam might cause cables' overheating. Are any of the 2 claims true? If yes and using expanding foam is not recommended then what is a standard solution in such cases?

A picture of the hole is here:

 

[Jackrae]

That's not your only problem. That junction box doesn't comply with requirements if it cannot be routinely inspected after the plasterboard is replaced

 

[ban-all-sheds]

The main goal of the whole renovation is to insulate the room and obviously I have to fill the hole to make it airtight.

No - that hole will be behind the plasterboard, and therefore behind the VCL - you don't need to plug it.

I've read somewhere (don't remember where exactly) that the ordinary polyurethane foam slowly reacts chemically with the cables insulation.

No - that's polystyrene. AFAIK PU foam is fine.

Additionally the foam might cause cables' overheating.

Unlikely over such a short distance, ditto the bunching, although due diligence should be done.

What are the cables for, and what are the ratings of the fuses/MCBs?


[EDIT]Spleling misteak corretced[/EDIT]

 

[Robin0577]

That's not your only problem. That junction box doesn't comply with requirements if it cannot be routinely inspected after the plasterboard is replaced

True, but it may well have complied when it was installed, so whilst it might be a good idea to change it, it might not be a requirement.

Equally, the fact that the cables run in the wall cavity at all is non-compliant now, but may not have been when they were put there.

P.S. On the "top" cable as seen in the photo, just by the joist, is that a bit of red core visible due to damage or is it just a stain/mark?

 

[securespark]

And have you got different Classes of cables in there?

 

[lookieluke]

The junction box might actually be redundant. The red core is exposed due to damage (not by me), this will need to be fixed. Regarding different classes of the cables and their purpose I don't really know. I can only guess these are for sockets and lighting. I would have to remove plasterboards from the ceilings of other rooms to find out exactly. Hopefully they are of proper thickness. The cables are in cavity because the house was built in 60's. There is the main fuse box in the adjacent room so I'm guessing the cables run in the cavities is relatively short. Not much of a consolation though.

I'm not going to sort out the cables. I will have an electrician coming round to sort out the cables. I asked him whether I can use the foam and wasn't sure so this is really the main concern for me now. The hole will be above the ceiling plasterboard, but the floor above it is not airtight so this will compromise the whole insulation exercise.

 

[JohnW2]

The main goal of the whole renovation is to insulate the room ... Additionally the foam might cause cables' overheating. ...?

Do I take it that your photo is rotated, and what we're looking at is a ceiling/floor joist and the underside of floorboards above? (BAS initially had me a bit confused when he talked of a VCL)

You've been given some answers about using expanding PU foam in the hole around cables, which would probably, in itself, be fine. However, is it your intention to fill the space between the (replaced ceiling and floorboards above with insulation. If so, that could have a bearing on the current-carrying-capacity of the cables (hence possibility of overheating), and is something you will need to discuss with your electrician.

Kind Regards, John

 

[seasickstevie]

I wouldn't want to leave it 'as is'. In essence you'll have just 12.5mm of pb between your ceiling and the cavity, and likely to end up with a patch of condensation and obvious loss of heat.

I'd really want to fill that aperture with a bit of rockwool at least. Probably foam is the answer.

 

[lookieluke]

I resolved the issue so for the interest and benefit of fellow diy-ers I thought I would post how it all ended up. My favourite electrician came round and found out that all the cables going through the hole are actually dead. More than that they were not attached to anything at one end so he basically pulled them out from the cavity. I have exactly the same situation at the other end of the house. The electrician that installed the new cabling just didn't bother to removed the old ones even though it was pretty simple thing to do. Oh well...

The hole is now tightly sealed with expanding foam so basically a happy end.

 

[Risteard]

True, but it may well have complied when it was installed

Not without the junction box and the cables being secured.