Is conduit necessary when hiding mains wiring in plaster?

Discussion in 'Misc DIY' started by LouisB, Jun 19, 2004.

  1. LouisB

    LouisB Guest

    Please can you help me.

    I want to know whether conduit is necessary when hiding mains wiring
    in plaster?

    The Collins DIY Manual (1986) says :-

    "Some people cover all buried cables with a channel but it isn't
    required by the IEE Regulations. Cables buried in light plastic
    conduit can be withdrawn later .. but the need is so rare in a house
    as to be hardly worth considering".

    If it is hardly worth considering why do shops sell conduit.?

    However a plasterer who visited our house said that all exposed cables
    should be covered by a conduit before plastering as the lime in the
    plaster can attack the cable insulation.

    Is this true?

    Please let me know what you recommend and whether I should use conduit
    to cover all the exposed wiring before plastering.

    Also what is the recommended depth that uncovered wiring should be
    placed below the plaster?

    Do you have any tips or tricks to avoid the need for conduit?

    Thanks Louis B.
     
    LouisB, Jun 19, 2004
    #1
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  2. LouisB

    Dave Jones Guest

    Why are u getting it plastered?
    Plasterboard is cheaper, quicker and will also save on the heating bills,
    and no need for conduit!

    Dave


    "LouisB" <> wrote in message
    news:...
    > Please can you help me.
    >
    > I want to know whether conduit is necessary when hiding mains wiring
    > in plaster?
    >
    > The Collins DIY Manual (1986) says :-
    >
    > "Some people cover all buried cables with a channel but it isn't
    > required by the IEE Regulations. Cables buried in light plastic
    > conduit can be withdrawn later .. but the need is so rare in a house
    > as to be hardly worth considering".
    >
    > If it is hardly worth considering why do shops sell conduit.?
    >
    > However a plasterer who visited our house said that all exposed cables
    > should be covered by a conduit before plastering as the lime in the
    > plaster can attack the cable insulation.
    >
    > Is this true?
    >
    > Please let me know what you recommend and whether I should use conduit
    > to cover all the exposed wiring before plastering.
    >
    > Also what is the recommended depth that uncovered wiring should be
    > placed below the plaster?
    >
    > Do you have any tips or tricks to avoid the need for conduit?
    >
    > Thanks Louis B.
     
    Dave Jones, Jun 19, 2004
    #2
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  3. LouisB

    chris French Guest

    In message <>, LouisB
    <> writes
    >Please can you help me.
    >
    >I want to know whether conduit is necessary when hiding mains wiring
    >in plaster?
    >

    No. But you can use it.
    >The Collins DIY Manual (1986) says :-
    >
    >"Some people cover all buried cables with a channel but it isn't
    >required by the IEE Regulations.
    >
    >If it is hardly worth considering why do shops sell conduit.?
    >

    Because some people find it worthwhile?

    >However a plasterer who visited our house said that all exposed cables
    >should be covered by a conduit before plastering as the lime in the
    >plaster can attack the cable insulation.
    >
    >Is this true?
    >

    No it isn't.

    >Please let me know what you recommend and whether I should use conduit
    >to cover all the exposed wiring before plastering.
    >

    I usually use oval conduit for my cables, it doesn't cost much or take
    much time, and the cable would need fixing anyway, and if I was to want
    to remove the cable I can. An alliterative is plastic capping, though I
    find that hard to fix on my walls. but you don't need to bother if you
    don't want to.

    >Also what is the recommended depth that uncovered wiring should be
    >placed below the plaster?


    So as the plaster will go over the top :) - it doesn't matter as long
    as you have a a few millimetres clearance,
    --
    Chris French, Leeds
     
    chris French, Jun 19, 2004
    #3
  4. LouisB

    LouisB Guest

    "Dave Jones" <> wrote in message news:<>...
    > Why are u getting it plastered?
    > Plasterboard is cheaper, quicker and will also save on the heating bills,
    > and no need for conduit!
    >
    > Dave


    Plasterboard is not really appropriate as the wires are in narrow
    channels cut in the old plaster by the electrictions.

    Louis B.

    > "LouisB" <> wrote in message
    > news:...
    > > Please can you help me.
    > >
    > > I want to know whether conduit is necessary when hiding mains wiring
    > > in plaster?
    > >
    > > The Collins DIY Manual (1986) says :-
    > >
    > > "Some people cover all buried cables with a channel but it isn't
    > > required by the IEE Regulations. Cables buried in light plastic
    > > conduit can be withdrawn later .. but the need is so rare in a house
    > > as to be hardly worth considering".
    > >
    > > If it is hardly worth considering why do shops sell conduit.?
    > >
    > > However a plasterer who visited our house said that all exposed cables
    > > should be covered by a conduit before plastering as the lime in the
    > > plaster can attack the cable insulation.
    > >
    > > Is this true?
    > >
    > > Please let me know what you recommend and whether I should use conduit
    > > to cover all the exposed wiring before plastering.
    > >
    > > Also what is the recommended depth that uncovered wiring should be
    > > placed below the plaster?
    > >
    > > Do you have any tips or tricks to avoid the need for conduit?
    > >
    > > Thanks Louis B.
     
    LouisB, Jun 20, 2004
    #4
  5. "LouisB" <> wrote in message news:...
    > Please can you help me.
    >
    > I want to know whether conduit is necessary when hiding mains wiring
    > in plaster?
    >

    <Snip>

    > However a plasterer who visited our house said that all exposed cables
    > should be covered by a conduit before plastering as the lime in the
    > plaster can attack the cable insulation.
    >
    > Is this true?
    >


    He may have said that because plasterers are notoriously sparks-unfriendly and will hack lumps out of bare cables or "hide" them for you if they're in their way. Not maliciously, but just because of the way they work and the tools they use.
    Plastic capping is a good idea if you're employing a plasterer - less chance of damage to the cables and it's cheap. Use galvanised nails to fix it though, or rust spots will come through.

    Plus I think capping gives *a little* more mechanical protection to the cables. Not much, but some!

    Si
     
    Mungo \two sheds\ Toadfoot, Jun 20, 2004
    #5
  6. Apologies for the formatting - I'll sort that!

    Si
     
    Mungo \two sheds\ Toadfoot, Jun 20, 2004
    #6
  7. LouisB

    Lurch Guest

    On 19 Jun 2004 12:20:55 -0700, (LouisB)
    strung together this:

    >I want to know whether conduit is necessary when hiding mains wiring
    >in plaster?
    >

    Not really, it just gets fitted as the norm.

    >"Some people cover all buried cables with a channel but it isn't
    >required by the IEE Regulations. Cables buried in light plastic
    >conduit can be withdrawn later .. but the need is so rare in a house
    >as to be hardly worth considering".
    >
    >If it is hardly worth considering why do shops sell conduit.?
    >

    Depends on what you mean by conduit, some types of trunking and
    conduit are for surface mounting, some are for flush mounting.

    >However a plasterer who visited our house said that all exposed cables
    >should be covered by a conduit before plastering as the lime in the
    >plaster can attack the cable insulation.
    >
    >Is this true?
    >

    Never heard that one before, wouldn't say it isn't true though. I'm
    sure someone will come along with some sort of chemical equation.

    >Please let me know what you recommend and whether I should use conduit
    >to cover all the exposed wiring before plastering.
    >

    I usually fit it, the regs only require it for mechanical protection
    during the plastering stages, e.g. the plasterer damaging it with his
    trowel, after that stage it's pretty useless at stopping nails and
    drill bits!

    >Also what is the recommended depth that uncovered wiring should be
    >placed below the plaster?
    >

    As long as it's below the surface, that'll do it.

    >Do you have any tips or tricks to avoid the need for conduit?
    >

    Not really, fit if you want, if not just clip the cable to the wall.
    --

    SJW
    A.C.S. Ltd
     
    Lurch, Jun 20, 2004
    #7
  8. LouisB

    Lurch Guest

    On 20 Jun 2004 01:05:47 -0700, (LouisB)
    strung together this:

    >Plasterboard is not really appropriate as the wires are in narrow
    >channels cut in the old plaster by the electrictions.
    >

    Plasterboard is attached to the wall with a 10-20mm gap behind it in
    which cables and pipes etc... can be run.
    --

    SJW
    A.C.S. Ltd
     
    Lurch, Jun 20, 2004
    #8
  9. LouisB

    Nige Guest

    In uk.d-i-y, Lurch wrote:

    >>Also what is the recommended depth that uncovered wiring should be
    >>placed below the plaster?
    >>

    >As long as it's below the surface, that'll do it.


    I'd suggest that the plaster depth is at least 3mm on top of the cable,
    otherwise it is easy to break.


    --
    Nige

    Please replace YYYY with the current year
     
    Nige, Jun 20, 2004
    #9
  10. On Sun, 20 Jun 2004 13:42:25 +0100, Mungo \"two sheds\" Toadfoot
    wrote:

    > Plastic capping is a good idea if you're employing a plasterer -
    > less chance of damage to the cables and it's cheap.


    Galvanised is cheaper still...

    --
    Cheers
    Dave. pam is missing e-mail
     
    Dave Liquorice, Jun 20, 2004
    #10
  11. LouisB

    Dave Stanton Guest

    < long line lengths removed>
    > Si


    Mungo

    Could you check your line lengths

    Dave

    --

    Some people use windows, others have a life.
     
    Dave Stanton, Jun 20, 2004
    #11
  12. LouisB

    Dave Plowman Guest

    In article <>,
    Mungo \two sheds\ Toadfoot <> wrote:
    > Apologies for the formatting - I'll sort that!


    It's ok here so I'd say you're within the permitted line length.

    --
    *Toilet stolen from police station. Cops have nothing to go on.

    Dave Plowman London SW
    To reply, change noise into sound.
     
    Dave Plowman, Jun 20, 2004
    #12
  13. LouisB

    John Guest

    "Lurch" <> wrote in message
    news:...
    > On 19 Jun 2004 12:20:55 -0700, (LouisB)
    > strung together this:
    >
    > >I want to know whether conduit is necessary when hiding mains wiring
    > >in plaster?
    > >

    > Not really, it just gets fitted as the norm.
    >
    > >"Some people cover all buried cables with a channel but it isn't
    > >required by the IEE Regulations. Cables buried in light plastic
    > >conduit can be withdrawn later .. but the need is so rare in a house
    > >as to be hardly worth considering".
    > >
    > >If it is hardly worth considering why do shops sell conduit.?
    > >

    > Depends on what you mean by conduit, some types of trunking and
    > conduit are for surface mounting, some are for flush mounting.
    >
    > >However a plasterer who visited our house said that all exposed cables
    > >should be covered by a conduit before plastering as the lime in the
    > >plaster can attack the cable insulation.
    > >
    > >Is this true?
    > >

    > Never heard that one before, wouldn't say it isn't true though. I'm
    > sure someone will come along with some sort of chemical equation.
    >


    IIRC the corrosion/material suitability chart which used to be doled out
    periodically with the Process Industry trade mags, such as whats new in
    processing, gave PVC as being resistant to most of the common reagents
    including quite "strong" alkalis and acids so its very unlikely that
    anything present in mortars or plasters will have any effect on PVC cable
    sheath. Now styrene vapours in quite low concentrations from polystyrene
    insulation is another matter altogether.
     
    John, Jun 20, 2004
    #13
  14. LouisB

    Lobster Guest

    "Mungo \"two sheds\" Toadfoot" <> wrote in message news:<>...
    > "LouisB" <> wrote in message
    > news:...


    > He may have said that because plasterers are notoriously
    > sparks-unfriendly and will hack lumps out of bare cables or "hide" them
    > for you if they're in their way. Not maliciously, but just because of
    > the way they work and the tools they use.


    Hey, tell me about it. Having completed my rewiring, I didn't fix any
    of the socket faceplates before getting the plasterer in last week, as
    otherwise I knew he'd just plaster them in, ie recessed below the
    surface - yuk. However, after he'd left I had to go round with hammer
    and chisel to hack out dried plaster from all the electric boxes...
    I'd have expected to have to break bits off the edge of the holes, but
    (despite there only being about 3mm of skim plaster here) this guy had
    managed to virtually fill all the boxes, some were barely even visible
    (and I knew where to look for the boxes!). By the time I'd fully
    re-exposed them all, I was left with plenty of damaged-edge holes
    which will polyfilla-ing before I can fit the faceplates... I really
    must go on that plastering course!

    David
     
    Lobster, Jun 20, 2004
    #14
  15. LouisB

    Nige Guest

    In uk.d-i-y, Dave Stanton wrote:

    >Could you check your line lengths


    Could you check your anal retention?


    --
    Nige

    Please replace YYYY with the current year
     
    Nige, Jun 20, 2004
    #15
  16. LouisB

    Dave Plowman Guest

    In article <>,
    Lobster <> wrote:
    > I'd have expected to have to break bits off the edge of the holes, but
    > (despite there only being about 3mm of skim plaster here) this guy had
    > managed to virtually fill all the boxes, some were barely even visible
    > (and I knew where to look for the boxes!). By the time I'd fully
    > re-exposed them all, I was left with plenty of damaged-edge holes
    > which will polyfilla-ing before I can fit the faceplates... I really
    > must go on that plastering course!


    You should have used a sharp old wood chisel and with care you'd not need
    to make good the edges.

    --
    *On the other hand, you have different fingers.

    Dave Plowman London SW
    To e-mail, change noise into sound.
     
    Dave Plowman, Jun 21, 2004
    #16
  17. On Mon, 21 Jun 2004 00:07:21 +0100, Dave Plowman wrote:

    > You should have used a sharp old wood chisel and with care you'd not
    > need to make good the edges.


    Or better cut round the outline of the boxes whilst the plaster was
    still "plastic".

    --
    Cheers
    Dave. pam is missing e-mail
     
    Dave Liquorice, Jun 21, 2004
    #17
  18. "Dave Stanton" <> wrote in message
    news:p...
    >
    >
    > < long line lengths removed>
    > > Si

    >
    > Mungo
    >
    > Could you check your line lengths
    >
    > Dave
    >


    Could you check the post I sent one minute after the first?

    Si
     
    Mungo \two sheds\ Toadfoot, Jun 21, 2004
    #18
  19. In message <>,
    Dave Plowman <> wrote:

    > In article <>,
    > Mungo \two sheds\ Toadfoot <> wrote:
    > > Apologies for the formatting - I'll sort that!

    >
    > It's ok here so I'd say you're within the permitted line length.
    >


    Nah he's not - look at the raw posting (save the raw message to a RAM
    disc and look at it in something like StrongEd or Zap with end-of-line
    markers turned on) and his paragraphs are each one long line - several
    hundred characters. IIRC the "netiquette" is to keep somewhere around 70
    chars and hard wrap (StrongEd's email settings hard wrap at 72
    characters). I suspect that Pluto is wrapping the lines for you.
    Messenger doesn't do that properly and splits words.

    We shouldn't pick on Mungo though; there are several people in this
    group who have the same problem.

    As for capping: I really can't see the point. The plastic stuff offers
    absolutely no protection whatsoever and is just as difficult to stick to
    the wall as cable clips, and the galvanised stuff *must* be earthed
    according to the regs, which is a bit of a painful process. As for being
    able to withdraw / replace cables, I have yet to meet the installation
    using capping where that is possible. There's usually a kink or a gap or
    a crushed bit or a couple of inches at ceiling level where the capping
    is missing. Not worth bothering IM(limited)E as you usually have to dig
    it out anyway!

    The oval conduit is slightly better, but means a deeper channel must be
    dug in the wall in order to be able to plaster over it. With just the
    cable and a few clips it is often possible to channel out just the
    existing plaster to give enough depth. Anything additional means hacking
    into a column of bricks or stones or blocks which can cause serious
    grief.

    Hwyl!

    M.

    --
    Martin Angove: http://www.tridwr.demon.co.uk/
    Two free issues: http://www.livtech.co.uk/ Living With Technology
    .... If you really want to know, you won't ask me.
     
    Martin Angove, Jun 21, 2004
    #19
  20. In message <>,
    Lurch <> wrote:

    > On 19 Jun 2004 12:20:55 -0700, (LouisB)
    > strung together this:
    >


    [...]

    > >However a plasterer who visited our house said that all exposed cables
    > >should be covered by a conduit before plastering as the lime in the
    > >plaster can attack the cable insulation.
    > >
    > >Is this true?
    > >

    > Never heard that one before, wouldn't say it isn't true though. I'm
    > sure someone will come along with some sort of chemical equation.
    >


    Just a possibility, but if it is the lime which attacks the (PVC) cable
    (do all plasters contain lime?) surely that would also attack PVC
    capping?

    [...]

    >
    > >Also what is the recommended depth that uncovered wiring should be
    > >placed below the plaster?
    > >

    > As long as it's below the surface, that'll do it.
    >


    *So long* as it is run within the "permitted zones". Outside these zones
    you must either bury it more than 50mm deep or mechanically protect it -
    and this doesn't mean plastic capping.

    Hwyl!

    M.

    --
    Martin Angove: http://www.tridwr.demon.co.uk/
    Two free issues: http://www.livtech.co.uk/ Living With Technology
    .... I think not, said Descartes; and promptly disappeared.
     
    Martin Angove, Jun 21, 2004
    #20
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