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Sub Main in Notched Joists. Your Opinion Please.

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Here we have a 16.00mmm2 T&E cable installed many years ago in a house, and it supplies a recently renewed consumer unit in an annexe. The cable runs under the first floor boards in notched  wooden joists. The boards are about 15mm thick. There is no mechanical protection apart from the wooden boards. The cable runs centrally to the floor boards  in the notched joists.


What is your opinion about leaving the cable where it is? It is backed up by a 60 Amp fuse in a switch fuse. There is no R.C.D. protection for the sub-main cable.


Z.


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    Notched joists was standard practice when I were a lad. Just as long as the notch was centred under a board so the nails could go safely each side then it was fine (as everyone knew in those days that you only nailed near the edges of the board - as nailing just in the centre wouldn't stop the natural timber boards cupping/twisting and was likely to hit cables or pipes). Nails from more random things like gripper strips or carpet tacks shouldn't go all the way through a standard thickness board.


    Nowadays it's a no-no of course, but for an existing, I'd suggest no worse than a C3 (e.g. similar cable concealed in wall without 30mA RCD protection, although the risks are probably somewhat less).


      - Andy.

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  • 0
    Notched joists was standard practice when I were a lad. Just as long as the notch was centred under a board so the nails could go safely each side then it was fine (as everyone knew in those days that you only nailed near the edges of the board - as nailing just in the centre wouldn't stop the natural timber boards cupping/twisting and was likely to hit cables or pipes). Nails from more random things like gripper strips or carpet tacks shouldn't go all the way through a standard thickness board.


    Nowadays it's a no-no of course, but for an existing, I'd suggest no worse than a C3 (e.g. similar cable concealed in wall without 30mA RCD protection, although the risks are probably somewhat less).


      - Andy.

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