Roof rafter weight calculation

Discussion in 'Builders' Talk' started by James V, Apr 20, 2015.

  1. James V

    James V Member

    Hi

    Just wondered if there is a website where rafter calculations can be done?

    I'm building a flat roof outbuilding using 2 x 4, which will be clad 2 layers thick on walls and roof with OSB. Sixe is 4.8 x 5.6m. The rafter span will be 4.8 metres, so the rafters will run this length; spaced 45cm apart, and with noggins at thirds. I'm planning to use 75 x 220 timber for the rafters. This would seem to be the right size based on a general span table (below) , but I'm wondering what impact by double thick OSB on the roof ill have on the dead weight? Would it fit the 'more than 0.75 but not more than 1' category, as per the table?

    Incidentally I'm building a music practice room, hence the double thickness board (there will be another independent frame inside this one too; also clad in double thickness boards)

    Any thoughts appreciated! I'm not going through planning or building control as I'm just under scope.

    James


    Span calculations.JPG
     
  2. chippie244

    chippie244 Super Member

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