Kit house extension

vini · Oct 5, 2012

Hi, I'm from Scotland so excuse the ignorance of laws in England, like the Part P stuff. I was on a job today, an extension and the builder was erecting a wooden frame and wooden skin with a cavity and then a course of brick. Between the wooden skin and the gyproc for the interior he was putting in king span insulation. Now he said to me that the architect had called for wiring to be installed in the cavity between the wooden skin and the course of brick work to prevent holes being drilled through the stud work for the running of cables. Apparently this is how builders are now being requested to do it.

Personally I would run the cables under the floor and up through the wooden frame to the sockets etc. I did not understand the idea of running cables on the outside of the wooden skin and then creating a hole from the brick work cavity through the wood, which I assume would or could create damp spots.

Am I missing something? Has there been a change in the way wiring of kit house is to be done from now on or has the builder read something and got the wrong end of the stick? Is it to do with Part P building regs, which so far haven't applied in Scotland?

Farmelectrics · Oct 5, 2012

Not aware of any change and I'd run the ables the same way as you

chrish_1977 · Oct 5, 2012

I am sure that in the regs it states that you cannot run cables in a cavity, do that would be that for me.

Chris

Sparkystu79 · Oct 6, 2012

Your builder/ architect has misunderstood I think. The new regs require a service void to be installed between the kingspan and internal gyproc so no cables pass through the insulation. So he is correct in saying no holes should be drilled in the frame but there should be a secondary frame installed for this purpose.

vini · Oct 6, 2012

So to my mind that means if the studs are 100mm in depth and the kingspan is 75mm then the kingspan goes against the outer wooden skin leaving a depth of cavity between the gyproc and kingspan of 25mm where my cables will be situated.

Of course the kingspan could be 100mm and they have given no thought as to how the poor electrician is going to get his cables to the sockets.
If the kingspan is against the gyproc it means I would have to cut into it in order to postion my back boxes and have cable running through it.

There is no way they are erecting a secondary frame for my cables. Sometimes when you ask for such things joiners just give a look as though you had asked if you could swing from a chandelier with his wife.

Sparkystu79 · Oct 6, 2012

Usually once the kingspan is fitted a vapour barrier is pinned across the front of the kit internally. Then 2"x1" battens are nailed onto the studs which then creates the service void for cables and pipes.