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independent ceiling span of 4m, 400 centres, size of joist?

Discussion in 'Building Regulations and Planning Permission' started by Casterbridge, 23 Jul 2013.

  1. Casterbridge

    Casterbridge

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    Independent ceiling at 400mm centres, span of 4m. Will hold 2 x 12.5mm fireboard - total plasterboard weight 20kg/m3. Also some insulation taking the total static load to less than 30kg/m3. No live load as the floor will remian in situ above.

    Are there any tables for the size of ceiling joists for the ceiling for c16 or c24 timber. I can only find floor joists, not ceiling joists (I assume the pure static load will allow me to use smaller joists that for a floor?)
     
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  3. noseall

    noseall

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    Use 100mm x 50mm with a central binder strapped to the existing ceiling joists.
     
  4. tony1851

    tony1851

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    The older editions of Approved Document A have the tables for ceiling joists.

    Looking at mine it says 7x2s C16 would be OK for 3.72 m for dead load 0.25 to 0.5 KN/sq m. (your 2 layers pb'd will fall in this range).

    But these figures allowed for a small live load (loft storage) of 5lbs/sq ft,
    so you should be well-OK on a 4m span with no load other than dead load.

    Or cheaper as Noseall said to use smaller joists and suspend mid-span?
     
  5. Casterbridge

    Casterbridge

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  6. tony1851

    tony1851

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    That's about right - my table for C24 on that span says 3.99m.
    But C24, although a stronger timber, does have a tendency to twist slightly - more so than C16.
    If you don't want to use hangers, just use 7x2s @ 400.
     
  7. freddiemercurystwin

    freddiemercurystwin

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    The tables and the info on the PDF you linked to is all taken from the original TRADA span tables so is reliable. 7x2's as mentioned will be fine.

    The old 1992 version of the building Regs Part A is available to view on the Planning Portal.
     
  8. Casterbridge

    Casterbridge

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