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Wall Cavity Wiring.

Zoomup
Good morning on this bright and sunny start,


                          Q. Which regulation(s) specifically prohibit(s) the installation of cables in brick and block cavity walls within the cavity?


in a, Older premises?


    b, Newer premises?


If regulations exist, what reasons are provided for the prohibition? Or are we just concerned about chemical damage of cable insulation if the cables are in contact with some types thermal insulation?


Z.
  • 0
    That thought led me to do an internet search for carbide caving lamps, apparently they are banned in many caves, I guess the biggest issue with them was people writing their names and drawing pictures on the walls in soot like prehistoric cave men.


    You just can’t do that with electric lamps.


    Andy
  • 0

    sparkiemike:




    Zoomup:




    sparkiemike:

    522.8.1




    Damage to cable sheaths can be avoided by careful installation.


    Z.


     




    But how do you know if you can't see it. It does not take much to tear the sheath on some T&E


     




    Years of experience and the "feel" of the cable as it is installed. Cable tested afterwards.


    Z.

  • 0

    Chris Pearson:

    So much for safe zones!




    The cable was more than 50mm from the wall surface wasn't it? Blind wall drilling is always a risk.


    Z.

  • 0

    Where is all of this water coming from Andy?



    Rain - penetrating the outer leaf - as most masonry materials aren't completely water tight. Breaking that path was the original purpose for having a cavity in a cavity wall after all. Try some building text books or the building regs.


       - Andy.
  • 0

    Zoomup:


    Years of experience and the "feel" of the cable as it is installed. Cable tested afterwards.


    Z.



     




    You must have long arms if you can feel it all the way down a cavity. ?

  • 0
    Given that very few single skin brick walls such as found on garages and better class sheds and so on actually have water running down the inside and even fewer houses with solid walls of double brick construction suffer from anything more than damp that can be mitigated by good ventilation, I think the water in cavity problem is not as bad as  suggested - if it was we would be drilling holes to make extra weep vents and seeing water pee out in a vigorous jet on those buildings that have them, and this is not the case.

    It is clearly a bad idea to bridge the cavity, and there are a few spectacular cases where the building has had serious problems already and adding blown fibre wall insulation has basic filled the cavity with something like soggy cotton wool. I suspect an odd length of T and E won't make that much difference, it is scarcely a good wicking material.
  • 0

    sparkiemike:




    Zoomup:


    Years of experience and the "feel" of the cable as it is installed. Cable tested afterwards.


    Z.



     




    You must have long arms if you can feel it all the way down a cavity. ?


     




    A cord with a lead mouse on the end naturally falls from wall plate to base of wall in the cavity, or to the hole for a socket box below. The cable is carefully pulled using the cord. This is easier if two people are installing the new cable, one pulling the cord  and the other feeding in the cable from above, but one person can do it, a bit like pulling in cables into conduit. No damage occurs at all as the route is normally free of obstructions and the cable runs freely.


    Z.

  • Former Community Member
    0 Former Community Member
    You could always consider the intent of Regulation B.7 in the 14th.......................


    Regards


    BOD
  • Former Community Member
    0 Former Community Member
    Fauna?


    Regards


    BOD
  • 0
    So you're lying on a bit of board spread across the top of the ceiling joists having pulled the fibreglass insulation back trying to drop a fishing line down the cavity over the top of the wall plate when you discover the brickies sealed the top of the cavity,  just like they are supposed to.


    Andy

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