Stringing CAT5 cable through a false ceiling.

Discussion in 'Home Networking' started by Stroller, Feb 20, 2008.

  1. Stroller

    Stroller Guest

    Hi there,

    I'm normally a software guy - setting up file- & print-sharing, ADSL
    routers, a bit of mail-servers & Windows SQL & domain servers, bugs in
    Internet Exploder & what-have-you - but much to my chagrin I have taken on
    a job CAT5 cabling a small office.

    There's already conduit in place, so on first sight the job looks as easy as
    running the network cables down that and clicking additional patresses into
    place. I've wired CAT5 cable to faceplates before, so that's no problem.

    However, there are a couple of doors in the way where there's no conduit and
    the CAT5 cables all have to lead back into a partitioned room, so there's
    obviously a little more to it than such a naive approach.

    If we're lucky we can run cables vertically downwards through the walls -
    which are clearly hollow, and the cavity of which can be accessed from
    above the false ceiling. A spanner or other small weight will hopefully
    allow us to lower a length of fishing line through the cavity and meet up
    with a hole drilled through the back of the existing conduit and through
    the plasterboard. We can then pull the CAT5 cable through with the fishing
    line. The electrician has already run his 240v mains cable through the
    cavity walls, although it's not apparent if he put the cables in place
    before the walls were erected, or used a similar method to that I outline.

    However in order to come across from the partitioned storage space to the
    correct position above the conduit, we have to run through the false
    ceiling, and I thought I'd ask here for any pointers from people who have
    already done this sort of thing - there must be lots of you!!

    My original idea was to stand on a step-ladder, lift one of the ceiling
    panels and pass the bundles of network cables from one side to the other.
    Rinse & repeat with the adjacent ceiling panel all the way across the room.
    This seems a bit arduous and it occurred to me to do the same with a
    length of fishing line and then use this to pull the bundle of cables all
    the way across the room.

    Finally, from a high vantage point with my head and shoulders all the way
    through the false ceiling, I realised that there's a lot of free space up
    there, so one could potentially tie one's fishing line to a rubber dog-bone
    and throw that at least halfway across the attic space. An acquaintance is
    a mechanic, much handier with drilling and cutting holes in things than I
    am and he has agreed to help me with this job - he suggests threading the
    fishing line through a pencil rubber and using a catapult to fire that
    across the ceiling space. Fishing catapults are designed to accurately drop
    tempting samples of fishing bait around a baited hook some 20 metres away,
    so should have sufficient range.

    Laid across the top of the false ceiling is some quite modern insulation -
    the office is a very recent conversion of an agricultural building - which
    has a "duvet cover" of thin fabric, so I don't think there'd be any problem
    with the bundle of CAT5 cables catching on it when pulled across it with
    the fishing line.

    How do other people do this? I assume people must run network cable through
    false ceilings all the time. Do you just laboriously lift one tile at a
    time, or is there a "trick" to it? I would imagine that those who have
    undertaken jobs like this many more times than I have will have discovered
    some shortcuts and some gotyas.

    The office is 9 metres by 13 metres in size. There's already some electrical
    cables strung up there. My acquaintance asks if the false ceiling is strong
    enough to take the weight of a bundle of a dozen or two network cables
    strung across them? Should we stick to the edges of the ceiling instead,
    and secure our cables to the walls? I have no idea. "What about mice?" he
    asks - I don't know that there's much we can do about that - surely no-one
    uses conduit in attic spaces?

    Many thanks in advance for any pointers or suggestions,

    Stroller, Feb 20, 2008
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  2. Stroller

    ric Guest

    it's not entirely normal* to have long lengths of cable strung across
    areas unsupported. normally you'd get or fabricate a cable tray and
    bolt it to something firm and run the cables along that, with cable
    ties keeping them attached and tidied down every few meters.
    you should also bear in mind good practice for network cables - don't
    run them parallel to mains power cables to avoid interference, cross
    power cables at 90 degrees if possible, and try and avoid extremely
    tight-radius bends in the cable. obviously it's probably going to
    work even if you avoid this, but this is good practice.
    you should also bear in mind that fire regs may get upset if you
    string cable that isn't flame-retardant (plenum) cable that could
    potentially cause fire in one area to be carried through the ceiling
    cavity to another area of the building. your clients' building
    insurance may specify this...

    i don't claim to stick to any of this in my own house, mind.

    * that is, it's common, but not particularly good practice!
    ric, Feb 20, 2008
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  3. Stroller

    Devs Guest

    My deepest condolences!! You need cable rods and tape. They're a bit
    like the drain rods used by plumbers. You'll get them at electrical
    suppliers. The roof will easily tale the weight of the cables. Dog bones
    and catapults and many other ingenious methods will work but won't be as
    efficient. I used to use an old telescope fibreglass fishing rod with
    some success!
    It is unlikely that you'll get cables down the walls, however. There
    will be noggins in the way unless they are lathe and plaster (old
    buildings only). You'll most likely have to run some surface trunking up
    to the ceiling or make a mess in the plaster board and repair later.
    Devs, Feb 20, 2008
  4. Stroller

    Clint Sharp Guest

    Cruel. Funny, but cruel.

    I hate to see software guys suffer, unless it's by my hand of course.
    Seconded on this one. If you have an old fishing rod.

    You can buy cheap 5Mtr+ telescopic rods for under a tenner. Decathlon if
    you have one near you, sell some cheap five, six and seven metre poles
    that are ideal.

    The whip section from an old CB/Taxi antenna is quite useful for cavity

    Be aware, carbon fibre fishing rods and whip antennae will conduct
    electricity so be *very* careful not to find any bare wires.

    As someone else mentioned you may need to be mindful of fire barriers
    if you are putting cables through solid walls or fire resistant
    Never seen a building that had lathes in the walls, laths often ;-)
    Clint Sharp, Feb 21, 2008
  5. Stroller

    Jon Guest

    I'd go with the first method, just move the tiles one at a time and
    allow the cable to rest on the upside of the suspended cieling.
    Should be fine, the cieling will be suspended with strong "fishing
    line" or metal wires.
    Jon, Feb 22, 2008
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