First jack rafter measurement.

Discussion in 'Carpenters' Talk' started by Ed wood wood wood, Sep 21, 2019.

  1. Ed wood wood wood

    Ed wood wood wood New Member

    im having trouble with the first jack rafter measurement to keep all the rafters on 400 centres.

    Can anyone advise ?

    Thanks
     
  2. Shytot

    Shytot Active Member

    Your last rafter should abut the hip at the ridge , then all you do is hook your tape on the last rafter and mark 400mm across onto the hip , put a pencil mark on the hip. Then measure from pencil mark to a 400mm mark on the wall plate.. Or you can use a ready reckoner, in the book it tells you how much jack rafters decrease by ..
    what’s the pitch of your roof ?
     
  3. Ed wood wood wood

    Ed wood wood wood New Member

    Thanks shytot

    My roof is 42 so my jacks decrease 538 mm

    But from what point on the jack side cut do I measure?
    Long side , middle or short side.

    Cheers
     
  4. Shytot

    Shytot Active Member

    I measure from the long side . Just treat it exactly the same as you cut your common rafter, what ever method you use to measure a CR do exactly the same for Jacks .
     

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