floor joist loading, spacing sizing span tables

Discussion in 'Wood / Woodwork / Carpentry' started by StephenStephen, 4 Feb 2015.

  1. StephenStephen

    StephenStephen

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    Old house (1725) , rubblestone wall, huge victorian timbers down centre of downstairs room ceiling. I'm looking up at ceiling (woodfibre ceiling now removed)
    Joists span between wall and central timber: clear span 2.29m

    joists (victorian pine I think) ends have rotted out, I found previous 'repair by sistering' with new timber ends supported on lime plaster.
    It's a mess, only 2 joists long or strong enough for span from central timber to stone wall, lots of worm and spongy wood, double and triple sistering with odd bits of this and that. (Except that there are 2 newer 7" by 2" joists well supported and in good condition.)

    So, new joists, and looking to decouple floor above from ceiling, so thinking separate ceiling and floor joists, or resilient bars, to soundproof.
    I'd rather not make new slots in the wall for joist ends so that means joist centres at 600mm

    looking at: http://www.dfpni.gov.uk/d.pdf page 12, and at http://www.diynot.com/forums/viewtopic.php?t=259050&start=15 RonnyRaygun page 2 of thread

    It looks like:
    Floor joist loads without ceiling: (kN/sq metre)
    Boards 0.15
    Joists 0.15

    Total dead load therefore 0.3
    clear span is 2.29m

    Therefore (looking at table) at C16 I could use 38mm by 145mm joists (6" by 1.5")
    So floor joists 7" by 2" would be more than adequate?

    And if I decided to use resilient bars, instead of separate ceiling joists, I would be adding the dead load of the ceiling , plus sound/thermal insulation fleece eg: http://www.thermafleece.com/product/thermafleece-ultrawool

    ceiling: 0.1 (kN/sq m)
    ultrawool at 50mm weighs 3.1kg/m sq = 0.31 kN/m sq

    so the total load would be increased by 0.41

    = 0.7
    so I could still use 38 by 145 (6" by 1.5")
    So combined floor and ceiling joist of 7" by 2" would still be more than adequate?

    Any thoughts?
    Many thanks,
    Stephen
     
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  3. StephenStephen

    StephenStephen

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    ...just wondering if this is in the right forum, or should I put it in 'building'?
     
  4. freddiemercurystwin

    freddiemercurystwin

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    What a long winded posts, you are over-thinking it all, for any domestic floor you will not go far wrong if you use the centre loading so between 0.25 and0.50. Then use your span/centres to determine the size. So anything above 38x147 @600 centres will be OK. Obviously bigger is best to minimise bounce.

    But yes no responses because you’re in Woodwork not Building where the SE’s hang out.
     
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