Bird mouth size using 8x2 timber

Discussion in 'Carpenters' Talk' started by CFK, Jul 30, 2016.

  1. CFK

    CFK New Member

    Hi just wondering whats the size limitation for cutting out birds mouths in 8x2 cls timbers for joists. It will also give me an idea of what size wall plate to use. This is on a 17.5 to 18 degree pitches roof.
     
    CFK, Jul 30, 2016
    #1
  2. Ed Ugarte

    Ed Ugarte New Member

    As a general rule of thumb the birds mouth is 1/3 the timber thickness.
     
    Ed Ugarte, Jul 30, 2016
    #2
  3. CFK

    CFK New Member

    Thanks for the reply Ed. So id get away happily with using a 3x2 cls wall plate and notching out a 1.5"w x 2.5"h birds mouth?
     
    CFK, Jul 30, 2016
    #3
  4. Phil the Paver

    Phil the Paver Screwfix Select

    The wall plate should be 100 x 50mm, you would cut the bird mouth out to suit the angle of the rafter.

    birdsmouth-joint-on-roof-truss-notched-into-floor.jpg

    The horizontal cut being 100mm or what ever the exact mm is (96) ?
    The depth (vertical) is then determined by the angle.
     
    Phil the Paver, Jul 30, 2016
    #4
    FatHands likes this.
  5. yozzer

    yozzer Member

    I thought all wall plates should be tanalised ?
     
    yozzer, Aug 7, 2016
    #5
  6. CFK

    CFK New Member

    I'll be using C16 timber same as the joists.
     
    CFK, Aug 7, 2016
    #6
  7. KIAB

    KIAB Super Member

    You can get tanalised C16/24.:)
     
    KIAB, Aug 7, 2016
    #7
  8. sospan

    sospan Screwfix Select

    I tend to use mainly tanalised for all structural work where I can. Not just because it is treated but because I find it is better quality and worth paying the difference
     
    sospan, Aug 8, 2016
    #8
    KIAB likes this.

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