Can I Use My Cavities...

[Silver_Hawk]

Hi,

Newcomer here...although been lurking for a few weeks.

Recently moved into a large brick-built house that was built in 1951. Only one previous owner and he was the builder/surveyor so things are not your normal standard box shape but the walls are massively thick with wide cavities between inner and outer. Ground floor is mostly solid i.e. no floorboards.

The wiring is all over the place; sockets seem to have been added randomly over the last 50 years; some of the cabling looks modern (plastic coated T+E) but so far, no sign of any ring mains. It has a quaint 1950's fuse box which the Science Museum would probably like. Probably my first job is to get a modern consumer unit fitted.

I want to replace all wiring starting with a dedicated ring main for the new kitchen (I know about Part P). All existing wiring seems to be using the cavities as conduits --- but I've read that this is no longer considered good practice due to damp potentially breaking down insulation over time etc.

What's the view here? Do I really have to start cutting channels in these solid walls for conduits; I'm not concerned with the disruption or mess, but it just seems a shame to start hacking away at this very fine brickwork when there seems to be these wide and dry cavities between inner and outer.

Cheers

Paul

 

[breezer]

as you said

I've read that this is no longer considered good practice due to damp potentially breaking down insulation over time etc.

you have answered your own question

 

[Silver_Hawk]

I take it thats a "No" then...

Why do so many of your replies seem so un-constructive? I guess I was hoping for a bit of a discussion, you know, pros vs cons....

But maybe it really is that clear cut... "in 2005, under no circumstances should wall cavities be used to lay cables"

 

[breezer]

Why do so many of your replies seem so un-constructive?

i wasnt meant to seem to be unhelpful, i just do not see the point of telling you something you already know.

 

[Silver_Hawk]

Why do so many of your replies seem so un-constructive?

i wasnt meant to seem to be unhelpful, i just do not see the point of telling you something you already know.

OK, thanks! I guess I was hoping for the slightest reason that could justify me using the cavities.

 

[baldelectrician]

The answer, as already stated is a big NO

The reson is that a cable in an external cavity wall may be surrounded by cavity wall insulation and the cable may go up in flames as a result.

Also you cannot ensure support for vertical drops when dropping cables down cavities

 

[plugwash]

as has been said its not good practice to put cables in cavities

However if there is already a load of wiring in the cavities then i can't see too much harm in adding more, if cavity wall insulation were to be desired you'd have to rewire to get the existing cables out of the cavity anyway.

on the other hand if you plan this to be the first part of a project to rewire the house then i'd try to keep it out of the cavities, another idea would be to avoid cavities in the kitchen itself but use them in other places on a temporary basis until you redo the rooms between the kitchen and the fusebox.

 

[baldelectrician]

What's the point of doing a job twice?
If you are going to rewire better to do it right rather than tell the wife you are going to rip the walls to bits in a couple of years rather than now when you are doing other work

Guidance note 1
7.2

Where a cable is to be run in a space in which thermal insulation is likely to be placed, the cable shall wherever practicable be fixed in a position such that it will not be in contact with or be covered by the thermal insulation. Where fixing in such a position is impracticable the cross sectional area of the cable shall be appropriately increased.

at the end of the section it specifically states

Thus, the introduction of thermal insulation into cavities where cables are already installed will create the possibility of overheating the cable. The extent of the risk will depend on the type of thermal insulation used and the total loading of the cables.

 

[andy]

Can I Use My Cavities...

do as you wish, just when your at the airport, be worred if you see any sniffer dogs...