Rewiring upstairs lighting in a flat roofed house

Discussion in 'Electricians' Talk' started by unphased, Jul 1, 2010.

  1. unphased

    unphased Screwfix Select

    I am pricing a rewire job. Three bed semi. The house is unusual in that it has no loft but instead a flat roof! My concern is, therefore, how to wire the upstairs lighting circuit without the benefit of a loft. I have been trying to work out the easiest way of running a wire from the switch to the light point if I wire the circuit by feeding the switches so I only need to worry about running one wire to the ceiling rose. I have to assume that I won’t be able to fish a wire through incase the joists aren’t in my favour so I was wondering about notching the plasterboard at the joist which can be easily patched up. Before you all throw your hands up in horror, my reasoning is who would ever want to hammer a nail through a ceiling after its all finished and decorated? I can fully understand not doing this on new builds where the ceiling boards have to be nailed up, but in this situation I really cannot think of any reason why notching the plasterboard (not the joist) would be dangerous. It is the obvious way forward on this one else it could be a very awkward job. So your views are requested please, perhaps you have done one of these before and can tell me how you did it? Surface trunking across the ceiling is not an option.

    Thanks
  2. Lucky

    Lucky New Member

    Hello Un

    If the joists are running against you so to speak , I`d cut a strip of Plasterboard out across the Ceiling maybe 12" wide , then drill the joists about 50-60mm up with a 25mm or so Short augur , the Holes maybe on the skew , but MUCH better than notching or clipping under P-Board , it`s just as easy to repair a 12" strip as a narrow un !


    Lucky
  3. Just_Another_Spark

    Just_Another_Spark New Member

    I concur with that. Take a whole thin length of plaster out, much easier to replace and patch up.
  4. unphased

    unphased Screwfix Select

    Hi lucky

    Your sugestion is a technique I have used in kitchen ceilings for downlighters but for a large area of the house it would be a fair amount of hassle. Do you not think my idea is acceptable?
  5. unphased

    unphased Screwfix Select

    Thanks J A S. :)
  6. gerrin2owd

    gerrin2owd New Member

    Consider the difference,
    cables coming down a wall plastered over or
    cables running across a ceiling plastered over.
    All cables will be protected by RCD
    What is the difference?
    Just do it mate.

    All this cutting 12" strips of plasterboard out drilling joists reboarding and skimming would take forever - forget all that ****.
  7. wally2

    wally2 New Member

    Hi un, the way ive done it in the past is to fish the way the joists go & fit coving all round & run the cables in that
  8. Accaman

    Accaman New Member

    Hi Roy.In cases like this or when floor above is tiled, i explain to customer that the ceiling will have to be chopped up a bit to deal with joists etc ,i then make good or get a local guy in to reboard ceiling which he does for a good price.If u cant get in from above what choice do you have,just make the customer see that!! :)
  9. Accaman

    Accaman New Member

    Hi Roy.In cases like this or when floor above is tiled, i explain to customer that the ceiling will have to be chopped up a bit to deal with joists etc ,i then make good or get a local guy in to reboard ceiling which he does for a good price.If u cant get in from above what choice do you have,just make the customer see that!! :)
  10. Lucky

    Lucky New Member

    Hello again Un.


    You`ll get a million and one answers on this , I`ve posted on how I`d do it , When pricing the job allow for a Local Plasterer to come out and infill etc , In my opinion it`s the only way to go , Advise the Customer thats the only way to go , or maybe Wall Lights all around ??? :)

    You`ll also be running a 3 core for an Interlinked Smokey as well I presume ??

    Or as a last alternative , why not try the new Wireless Lighting .... awesome !! ;)

    Lucky
  11. seneca2

    seneca2 New Member

    Hi un, the way ive done it in the past is to fish the way the joists go & fit coving all round & run the cables in that
    --------------------------
    As Wally say's UP or use the 150mm safe zone along the top of the wall, much easier to skim that over with a bit of bonding than making good the ceiling mate!
  12. Accaman

    Accaman New Member

    Thats all well and good providing you can get to your light locations without hitting joists or noggings/tightly packed insulation...;)
  13. unphased

    unphased Screwfix Select

    Thanks all for your replies. :)

    I think this should be raised as a comment in the new wiring regs amendments out for public comment. I cannot for the life of me see a problem with clipping a cable to the underside of a ceiling joist in the depth of the ceiling board. A ceiling should IMHO be made entirely a safe zone. It is a lot safer running a cable across a ceiling than down a wall! What hazards would exist for example? You don't hang pictures. You don't hang cupboards, if your kinky you might put a mirror on it :))) but can anyone seriously see why the practice of clipping a wire to the underside of a ceiling joist is no-no. It will also be RCD protected don't forget.


    I have discussed this at legth with the customer and told them I will utilize the 150mm of wall at the ceiling junction to run my wires and then fish across to the light point where joists run in favour of so doing. I have also allowed extra time on the job to make sure I have enough in the price. Will let you know if I get the job and how I get on.

    :)
  14. J.P.

    J.P. New Member

    I always thought that ceilings were safe zones UN?
  15. J.P.

    J.P. New Member

    Ie..if people go whipping in nails and PK's and stuff into the ceiling without checking if there are any cables above..its there fault if they blow summit up.

    Although must say it is imperative that the cables are RCD protected..but they will be under the 17th anyway. Flipping heck.

    TBQH honest if I had a job like that, upon re-iteration would be a bit stumped on the technique to use despite what I have written above. Hmmmmmm sounds like an interesting job. Maybe the ceiling will have to come down?..:)
  16. J.P.

    J.P. New Member

  17. BS-60898

    BS-60898 New Member

    presumably as it is a rewire they already have an upstairs lighting cct? I have just finished one with a concrete roof, all lights were singles in conduit with pull cord switches

    I just looped round the switches and chased down, used the 150mm round the roof to run the loops, pulled a new light feed through the conduit tied onto the old singles.... all you have to make good is the walls :)

    Guess yours has not got conduit/singles, if not tie onto the old cables and pull through the oe holes??
  18. unphased

    unphased Screwfix Select

    Hi BS

    You are correct that mine will not have conduit. Its a 1960's original wiring and its a traditional flat roof. The cables usually have those 'orrid metal cable clips that wrap around the wire so I doubt I will be able to use the old wiring as a puller. :(
  19. mr sillys

    mr sillys New Member

  20. seneca2

    seneca2 New Member

    The cables usually have those 'orrid metal cable clips that wrap around the wire
    ------------------
    Yes UP, 'buckle clips', you have no chance of pulling a cable out of those! I agree what you say about ceilings re making the whole area a safe zone. I have done what you're saying, ie brought the cable under the joist and then just filled it in on a few occasions, I know it's not correct but sometimes it just has to be done doesn't it? If it's rcd protected it's not such a bad thing to do, and remember, bs 7671 is 'guidance'.

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