Roof joist widths

Discussion in 'Builders' Talk' started by Mark8828, Apr 14, 2014.

  1. Mark8828

    Mark8828 New Member

    Hi guys, I'm putting a solid lean to roof on my conservatory with , 120mm by 47mm joists over a span of 3m from bolted on wall beam , covered in OSB board then synthetic roof shingles (keep weight down). Just wondering how far apart joists should be. Is it 600 centres like floor and roof or can I go wider , I'm planning on putting noggins in and then plasterboarding internal. Regards in advance
     
  2. Phil the Paver

    Phil the Paver Screwfix Select

    Personally for the size of timber being used, I would be looking at 400mm centre's:)
     
    FatHands likes this.
  3. Sean_ork

    Sean_ork Screwfix Select

    that's a very skinny timber - I'd not go any lower than 145 - even 195 - and put a rubber roof on it

    and don't be tempted to fill between the joists with insulation - and don't forget the VCL

    and and ......
     
    FatHands likes this.
  4. joinerjohn1

    joinerjohn1 Screwfix Select

    According to TRADA Span tables, you should be fine at 400mm centres. ;);)
     
  5. Sean_ork

    Sean_ork Screwfix Select

    at what loading ?
     
  6. joinerjohn1

    joinerjohn1 Screwfix Select

    Sorry Mark8828..Ignore my comment re- the TRADA Span tables, I'll leave it to the self proclaimed expert on here, to advise you.
     
    Deleted member 33931 likes this.
  7. Phil the Paver

    Phil the Paver Screwfix Select

  8. I usually do it at 450 centre's
     
    Last edited by a moderator: Feb 19, 2015
  9. Phil the Paver

    Phil the Paver Screwfix Select

     
    Last edited by a moderator: Feb 19, 2015
  10. lol thats true, its the stud wall that I do 450's at so I can use full boards, I miss-read the thread your right with 400 for the ceiling :)
     

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