floor joist size for 6m span

Discussion in 'Misc DIY' started by zak mondo, May 24, 2004.

  1. zak mondo

    zak mondo Guest

    Hi, I've bought a 500 year old house in croatia that needs 2 new
    floors. The interior measures 6m x 6m. The original joists are really
    small and rotten. What size of joists would I need to have to span the
    room without support posts ? I don't think I will be able to get
    I-beams but could get timber in the following dimensions: 100mm x
    200mm or 140mm x 200mm. Would this be sufficient ? Cheers.
    zak mondo, May 24, 2004
    #1
  2. zak mondo

    BigWallop Guest

    "zak mondo" <> wrote in message
    news:...
    > Hi, I've bought a 500 year old house in croatia that needs 2 new
    > floors. The interior measures 6m x 6m. The original joists are really
    > small and rotten. What size of joists would I need to have to span the
    > room without support posts ? I don't think I will be able to get
    > I-beams but could get timber in the following dimensions: 100mm x
    > 200mm or 140mm x 200mm. Would this be sufficient ? Cheers.


    These sites should tell you all about it:

    http://www.diydoctor.org.uk/projects/load-bearing_walls.htm

    http://www.naturalhandyman.com/iip/infxtra/infload.shtm

    http://www.hometips.com/diy.html


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    BigWallop, May 24, 2004
    #2
  3. zak mondo

    Set Square Guest

    In an earlier contribution to this discussion,
    zak mondo <> wrote:

    > Hi, I've bought a 500 year old house in croatia that needs 2 new
    > floors. The interior measures 6m x 6m. The original joists are really
    > small and rotten. What size of joists would I need to have to span the
    > room without support posts ? I don't think I will be able to get
    > I-beams but could get timber in the following dimensions: 100mm x
    > 200mm or 140mm x 200mm. Would this be sufficient ? Cheers.


    I'm sure that some of the experts will quote chapter and verse from the
    loading tables - but 6 metres seems a hell of a span to do in one go. From
    the top of my head, I reckon you would need something with a vertical
    dimension considerably in excess of 200mm.

    Are you *sure * you can't get an I-section RSJ? With a 200mm high RSJ across
    the middle of the room, you could cut 200x50 joists into it - so the RSJ
    would be within the ceiling depth and would be hidden. The joist span would
    then only be 3 metres - which is fine.
    --
    Cheers,
    Set Square
    ______
    Please reply to newsgroup. Reply address is Black Hole!
    Set Square, May 24, 2004
    #3
  4. zak mondo

    John Rumm Guest

    Set Square wrote:

    >>Hi, I've bought a 500 year old house in croatia that needs 2 new
    >>floors. The interior measures 6m x 6m. The original joists are really
    >>small and rotten. What size of joists would I need to have to span the
    >>room without support posts ? I don't think I will be able to get
    >>I-beams but could get timber in the following dimensions: 100mm x
    >>200mm or 140mm x 200mm. Would this be sufficient ? Cheers.


    It depends on what you would consider to be an allowable maximum
    deflection for the floor. In the UK you are limited by building regs to
    about 0.003 * the length of the beam (or 14mm for beams over ~5m IIRC).
    Assuming there is no Croatian BCO standing over your shoulder and you
    can tollerate say 30mm deflection then you have a much simpler task.

    > I'm sure that some of the experts will quote chapter and verse from the
    > loading tables - but 6 metres seems a hell of a span to do in one go. From
    > the top of my head, I reckon you would need something with a vertical
    > dimension considerably in excess of 200mm.


    I would have thought that 140x200 would do a credible job at that length
    even if they did not reach UK standards for deflection.

    > Are you *sure * you can't get an I-section RSJ? With a 200mm high RSJ across
    > the middle of the room, you could cut 200x50 joists into it - so the RSJ
    > would be within the ceiling depth and would be hidden. The joist span would
    > then only be 3 metres - which is fine.


    The other possibility is a flitch beam - that would need a metal plate
    down the middle and wood either side all bolted together - but that may
    be more accessable than a full on I beam.


    --
    Cheers,

    John.

    /=================================================================\
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    \=================================================================/
    John Rumm, May 24, 2004
    #4

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